"Fix lib.types.derivations.shell's check" (#7)

"`lib.types.derivations.shell` uses `lib.packages.isDerivation` but didn't passed an argument, making code using it fail with `error: value is a function while a Boolean was expected`"

Co-authored-by: Austreelis <dev@austreelis.net>
Reviewed-on: auxolotl/labs#7
Reviewed-by: isabel roses <isabel@isabelroses.com>
Reviewed-by: Jake Hamilton <jake.hamilton@hey.com>
Co-authored-by: Austreelis <austreelis@noreply.git.auxolotl.org>
Co-committed-by: Austreelis <austreelis@noreply.git.auxolotl.org>

format.sh

@@ -1,5 +1,5 @@
 #!/usr/bin/env nix-shell
-#!nix-shell -i bash -I "nixpkgs=https://github.com/nixos/nixpkgs/archive/nixos-24.05.tar.gz" -p nixfmt-rfc-style
+#!nix-shell -i bash -I "nixpkgs=https://github.com/nixos/nixpkgs/archive/nixos-unstable.tar.gz" -p nixfmt-rfc-style
 
 files=$(find . -name "*.nix" -type f)
 

foundation/flake.lock

@@ -3,10 +3,10 @@
     "lib": {
       "locked": {
         "dir": "lib",
-        "dirtyRev": "9850da8aa9dc9be22e237c9b424a18e801e53ecb-dirty",
+        "dirtyRev": "2be3111b2c0911f40b47fe0a1fb22b5f5188cf59-dirty",
-        "dirtyShortRev": "9850da8-dirty",
+        "dirtyShortRev": "2be3111-dirty",
-        "lastModified": 1718529861,
+        "lastModified": 1719251485,
-        "narHash": "sha256-tv/0C7ixH+9Ij+r+5nua48OlXXXnbdEsnenxX4eG/Sk=",
+        "narHash": "sha256-63NvfFVeTDITfNu60rmCUlaZtAeZUnvrIaOLSk9ScC8=",
         "type": "git",
         "url": "file:../?dir=lib"
       },

foundation/src/stages/stage1/gawk/boot.nix

@@ -68,6 +68,7 @@ in
             export CC="tcc -B ${stage1.tinycc.mes.libs.package}/lib"
             export ac_cv_func_getpgrp_void=yes
             export ac_cv_func_tzset=yes
+            chmod 0755 missing
             bash ./configure \
               --build=${platform.build} \
               --host=${platform.host} \

foundation/src/stages/stage1/gnutar/boot.nix

@@ -58,6 +58,7 @@ in
 
             # Configure
             export CC="tcc -B ${stage1.tinycc.mes.libs.package}/lib"
+            chmod 0755 missing
             bash ./configure \
               --build=${platform.build} \
               --host=${platform.host} \

foundation/src/stages/stage1/gnutar/musl.nix

@@ -59,6 +59,7 @@ in
           export ac_cv_sizeof_unsigned_long=4
           export ac_cv_sizeof_long_long=8
           export ac_cv_header_netdb_h=no
+          chmod 0755 missing
           bash ./configure \
             --prefix=$out \
             --build=${platform.build} \

lib/src/dag/default.nix

@@ -21,7 +21,7 @@ lib: {
       ## Apply a topological sort to a DAG.
       ##
       ## @type Dag a -> { result :: List a } | { cycle :: List a, loops :: List a }
-      topographic =
+      topological =
         graph:
         let
           getEntriesBefore =
@@ -43,7 +43,7 @@ lib: {
 
           isBefore = a: b: builtins.elem a.name b.after;
 
-          sorted = lib.lists.sort.topographic isBefore entries;
+          sorted = lib.lists.sort.topological isBefore entries;
         in
         if sorted ? result then
           {
@@ -95,7 +95,7 @@ lib: {
       ## Create a new DAG entry.
       ##
       ## @type List String -> List String -> a -> { before :: List String, after :: List String, value :: a }
-      between = before: after: value: { inherit before after value; };
+      between = after: before: value: { inherit before after value; };
 
       ## Create a new DAG entry with no dependencies.
       ##
@@ -105,12 +105,12 @@ lib: {
       ## Create a new DAG entry that occurs before other entries.
       ##
       ## @type List String -> a -> { before :: List String, after :: List String, value :: a }
-      before = before: lib.dag.entry.between before [ ];
+      before = before: lib.dag.entry.between [ ] before;
 
       ## Create a new DAG entry that occurs after other entries.
       ##
       ## @type List String -> a -> { before :: List String, after :: List String, value :: a }
-      after = lib.dag.entry.between [ ];
+      after = after: lib.dag.entry.between after [ ];
     };
 
     entries = {
@@ -121,7 +121,7 @@ lib: {
         tag:
         let
           process =
-            i: before: after: entries:
+            i: after: before: entries:
             let
               name = "${tag}-${builtins.toString i}";
               entry = builtins.head entries;
@@ -130,7 +130,7 @@ lib: {
             if builtins.length entries == 0 then
               { }
             else if builtins.length entries == 1 then
-              { "${name}" = lib.dag.entry.between before after entry; }
+              { "${name}" = lib.dag.entry.between after before entry; }
             else
               { "${name}" = lib.dag.entry.after after entry; } // (process (i + 1) before [ name ] rest);
         in
@@ -144,12 +144,12 @@ lib: {
       ## Create a DAG from a list of entries, prefixed with a tag, that occurs before other entries.
       ##
       ## @type String -> List String -> List a -> Dag a
-      before = tag: before: lib.dag.entries.between tag before [ ];
+      before = tag: before: lib.dag.entries.between tag [ ] before;
 
       ## Create a DAG from a list of entries, prefixed with a tag, that occurs after other entries.
       ##
       ## @type String -> List String -> List a -> Dag a
-      after = tag: lib.dag.entries.between tag [ ];
+      after = tag: after: lib.dag.entries.between tag after [ ];
     };
   };
 }

lib/src/dag/default.test.nix

@@ -119,11 +119,11 @@ in
   };
 
   "sort" = {
-    "topographic" = {
+    "topological" = {
       "handles an empty graph" =
         let
           expected = [ ];
-          actual = lib.dag.sort.topographic { };
+          actual = lib.dag.sort.topological { };
         in
         actual.result == expected;
 
@@ -147,7 +147,7 @@ in
               value = "d";
             }
           ];
-          actual = lib.dag.sort.topographic {
+          actual = lib.dag.sort.topological {
             a = lib.dag.entry.anywhere "a";
             b = lib.dag.entry.between [ "c" ] [ "a" ] "b";
             c = lib.dag.entry.before [ "c" ] "c";

lib/src/lists/default.nix

@@ -31,15 +31,15 @@ lib: {
         in
         builtins.map (x: builtins.elemAt x 1) (builtins.sort isLess prepared);
 
-      ## Perform a topographic sort on a list of items. The predicate function determines whether
+      ## Perform a topological sort on a list of items. The predicate function determines whether
       ## its first argument comes before the second argument.
       ##
       ## @type (a -> a -> Bool) -> List a -> List a
-      topographic =
+      topological =
         predicate: list:
         let
           searched = lib.lists.search.depthFirst true predicate list;
-          results = lib.lists.sort.topographic predicate (searched.visited ++ searched.rest);
+          results = lib.lists.sort.topological predicate (searched.visited ++ searched.rest);
         in
         if builtins.length list < 2 then
           { result = list; }
@@ -224,5 +224,11 @@ lib: {
         filter = result: value: if builtins.elem value result then result else result ++ [ value ];
       in
       builtins.foldl' filter [ ] list;
+
+    ## Flatten a list of lists into a single list.
+    ##
+    ## @type List (List a) -> List a
+    flatten =
+      value: if builtins.isList value then builtins.concatMap lib.lists.flatten value else [ value ];
   };
 }

lib/src/options/default.nix

@@ -43,7 +43,7 @@ lib: {
           resolve =
             definition:
             let
-              properties = builtins.addErrorContext "while evaluating definitions from `${definition.__file__}`:" (
+              properties = builtins.addErrorContext "while evaluating definitions from `${definition.__file__ or "<unknown>"}`:" (
                 lib.modules.apply.properties definition.value
               );
               normalize = value: {

lib/src/types/default.nix

@@ -49,18 +49,18 @@ lib: {
     ##
     ## @type Attrs -> Attrs
     create =
-      settings@{
+      settings@{ name
-        name,
+      , description ? name
-        description ? name,
+      , fallback ? { }
-        fallback ? { },
+      , check ? lib.fp.const true
-        check ? lib.fp.const true,
+      , merge ? lib.options.merge.default
-        merge ? lib.options.merge.default,
+      , functor ? lib.types.functor name
-        functor ? lib.types.functor name,
+      , mergeType ? lib.types.merge functor
-        mergeType ? lib.types.merge functor,
+      , getSubOptions ? lib.fp.const { }
-        getSubOptions ? lib.fp.const { },
+      , getSubModules ? null
-        getSubModules ? null,
+      , withSubModules ? lib.fp.const null
-        withSubModules ? lib.fp.const null,
+      , children ? { }
-        children ? { },
+      ,
       }:
       {
         __type__ = "type";
@@ -108,7 +108,7 @@ lib: {
           identifier = lib.options.getIdentifier location;
           first = builtins.elemAt definitions 0;
 
-          files = builtins.map lib.modules.getFiles definitions;
+          files = lib.modules.getFiles definitions;
           serializedFiles = builtins.concatStringsSep " and " files;
 
           getType =
@@ -118,13 +118,16 @@ lib: {
             else
               builtins.typeOf value;
 
-          commonType = builtins.foldl' (
+          commonType = builtins.foldl'
+            (
               type: definition:
                 if getType definition.value != type then
-              builtins.throw "The option `${identifier}` has conflicting definitions in ${files}"
+                  builtins.throw "The option `${identifier}` has conflicting definitions in ${serializedFiles}"
                 else
                   type
-          ) (getType first.value) definitions;
+            )
+            (getType first.value)
+            definitions;
 
           mergeStringifiableAttrs = lib.options.merge.one;
 
@@ -132,7 +135,7 @@ lib: {
 
           mergeList =
             if builtins.length definitions > 1 then
-              builtins.throw "The option `${identifier}` has conflicting definitions in ${files}"
+              builtins.throw "The option `${identifier}` has conflicting definitions in ${serializedFiles}"
             else
               (lib.types.list.of lib.types.any).merge;
 
@@ -140,10 +143,12 @@ lib: {
             location: definitions: x:
             let
               resolvedLocation = location ++ [ "<function body>" ];
-              resolvedDefinitions = builtins.map (definition: {
+              resolvedDefinitions = builtins.map
+                (definition: {
                   __file__ = definition.__file__;
                   value = definition.value x;
-              }) definitions;
+                })
+                definitions;
             in
             lib.types.any.merge resolvedLocation resolvedDefinitions;
 
@@ -200,7 +205,8 @@ lib: {
         ## @type Int -> Int -> Attrs
         between =
           start: end:
-          assert lib.errors.trace (
+            assert lib.errors.trace
+              (
                 start <= end
               ) "lib.types.ints.between start must be less than or equal to end";
             lib.types.withCheck lib.types.int (value: value >= start && value <= end)
@@ -317,7 +323,8 @@ lib: {
         ## @type Int -> Int -> Attrs
         between =
           start: end:
-          assert lib.errors.trace (
+            assert lib.errors.trace
+              (
                 start <= end
               ) "lib.types.numbers.between start must be less than or equal to end";
             lib.types.withCheck lib.types.number (value: value >= start && value <= end)
@@ -447,8 +454,7 @@ lib: {
     };
 
     attrs = {
-      ## A type that allows an attribute set containing any type of value. The merged
+      ## A type that allows an attribute set containing any type of value.
-      ## definitions must all be.
       ##
       ## @type Attrs
       any = lib.types.create {
@@ -480,10 +486,12 @@ lib: {
             let
               normalize =
                 definition:
-                builtins.mapAttrs (name: value: {
+                builtins.mapAttrs
+                  (name: value: {
                     __file__ = definition.__file__;
                     value = value;
-                }) definition.value;
+                  })
+                  definition.value;
               normalized = builtins.map normalize definitions;
               zipper =
                 name: definitions: (lib.options.merge.definitions (location ++ [ name ]) type definitions).optional;
@@ -520,10 +528,12 @@ lib: {
             let
               normalize =
                 definition:
-                builtins.mapAttrs (name: value: {
+                builtins.mapAttrs
+                  (name: value: {
                     __file__ = definition.__file__;
                     value = value;
-                }) definition.value;
+                  })
+                  definition.value;
               normalized = builtins.map normalize definitions;
               zipper =
                 name: definitions:
@@ -569,7 +579,7 @@ lib: {
       ##
       ## @type Attrs
       shell = lib.types.derivation // {
-        check = value: lib.packages.isDerivation && builtins.hasAttr "shellPath" value;
+        check = value: lib.packages.isDerivation value && builtins.hasAttr "shellPath" value;
       };
     };
 
@@ -606,9 +616,11 @@ lib: {
           merge =
             location: definitions:
             let
-              result = lib.lists.mapWithIndex1 (
+              result = lib.lists.mapWithIndex1
+                (
                   i: definition:
-                lib.lists.mapWithIndex1 (
+                    lib.lists.mapWithIndex1
+                      (
                         j: value:
                           let
                             resolved =
@@ -622,9 +634,12 @@ lib: {
                                 ];
                           in
                           resolved.optional
-                ) definition.value
+                      )
-              ) definitions;
+                      definition.value
-              merged = builtins.concatLists result;
+                )
+                definitions;
+
+              merged = lib.lists.flatten result;
               filtered = builtins.filter (definition: definition ? value) merged;
               values = lib.options.getDefinitionValues filtered;
             in
@@ -777,11 +792,11 @@ lib: {
       ##
       ## @type { modules :: List Module, args? :: Attrs, description? :: String | Null, shorthand? :: Bool } -> Attrs
       of =
-        settings@{
+        settings@{ modules
-          modules,
+        , args ? { }
-          args ? { },
+        , description ? null
-          description ? null,
+        , shorthand ? true
-          shorthand ? true,
+        ,
         }:
         let
           getModules = builtins.map (
@@ -790,9 +805,12 @@ lib: {
               let
                 # TODO: Figure out if we can apply additional attributes to the generated module.
                 # Currently this causes issues to do with redefined options.
-                rest = builtins.removeAttrs (lib.attrs.filter (
+                rest = builtins.removeAttrs
+                  (lib.attrs.filter
+                    (
                       name: value: builtins.elem name lib.modules.VALID_KEYS
-                ) definition.value) [ "freeform" ];
+                    )
+                    definition.value) [ "freeform" ];
               in
               if definition.value ? config then
                 rest
@@ -922,10 +940,12 @@ lib: {
           merge = location: definitions: {
             includes =
               modules
-              ++ builtins.map (definition: {
+              ++ builtins.map
+                (definition: {
                   __file__ = "${definition.__file__}; via ${lib.options.getIdentifier location}";
                   includes = [ definition.value ];
-              }) definitions;
+                })
+                definitions;
           };
           getSubOptions = submodule.getSubOptions;
           getSubModules = submodule.getSubModules;
@@ -961,10 +981,12 @@ lib: {
         location: definitions:
         let
           first = builtins.elemAt definitions 0;
-          modules = builtins.map (definition: {
+          modules = builtins.map
+            (definition: {
               __file__ = definition.__file__;
               options = lib.options.create { type = definition.value; };
-          }) definitions;
+            })
+            definitions;
           merged = lib.modules.fixup location (lib.options.merge.declarations location modules);
         in
         if builtins.length definitions == 1 then first.value else merged.type;
@@ -1100,6 +1122,43 @@ lib: {
           };
         };
 
+    ## Create a type that allows a value which is either the final type or is transformable
+    ## to the final type.
+    ##
+    ## @type Attrs -> (Any -> Any) -> Attrs -> Attrs
+    coerceWithLocation =
+      initial: transform: final:
+      let
+      in
+      if initial.getSubModules != null then
+        builtins.throw "lib.types.coerceWithLocation's first argument may not have submodules, but got ${initial.description}"
+      else
+        lib.types.create {
+          name = "Coerce";
+          description = "${initial.description} that is transformed to ${final.description}";
+          fallback = final.fallback;
+          check = value: final.check value || (initial.check value && final.check (transform [ ] value));
+          merge =
+            location: definitions:
+            let
+              process = value: if initial.check value then transform location value else value;
+              normalize = definition: definition // { value = process definition.value; };
+              normalized = builtins.map normalize definitions;
+            in
+            final.merge location normalized;
+          getSubOptions = final.getSubOptions;
+          getSubModules = final.getSubModules;
+          withSubModules =
+            modules: lib.types.coerceWithLocation initial transform (final.withSubModules modules);
+          mergeType = x: y: null;
+          functor = lib.types.functor "coerceWithLocation" // {
+            wrapped = final;
+          };
+          children = {
+            inherit initial final;
+          };
+        };
+
     dag = {
       ## Create a type that allows a DAG (Directed Acyclic Graph) of a given type.
       ##
@@ -1160,10 +1219,12 @@ lib: {
           merge =
             location: definitions:
             submodule.merge location (
-              builtins.map (definition: {
+              builtins.map
+                (definition: {
                   __file__ = definition.__file__;
                   value = normalize definition;
-              }) definitions
+                })
+                definitions
             );
         };
     };

tidepool/flake.lock

@@ -8,10 +8,10 @@
       },
       "locked": {
         "dir": "foundation",
-        "dirtyRev": "9850da8aa9dc9be22e237c9b424a18e801e53ecb-dirty",
+        "dirtyRev": "3f9d287065ac685ce500c2cddb35428b2927f5a2-dirty",
-        "dirtyShortRev": "9850da8-dirty",
+        "dirtyShortRev": "3f9d287-dirty",
-        "lastModified": 1718529861,
+        "lastModified": 1720514984,
-        "narHash": "sha256-X1Wd6mDz8GTaoxt1ylkvZfrJOcZtspJrEjXMtJ2ZyG0=",
+        "narHash": "sha256-AuixwSlYk34Z6+GEc7y4QotF3Hk963zC9I9hAwX5KCE=",
         "type": "git",
         "url": "file:../?dir=foundation"
       },
@@ -24,10 +24,10 @@
     "lib": {
       "locked": {
         "dir": "lib",
-        "dirtyRev": "9850da8aa9dc9be22e237c9b424a18e801e53ecb-dirty",
+        "dirtyRev": "3f9d287065ac685ce500c2cddb35428b2927f5a2-dirty",
-        "dirtyShortRev": "9850da8-dirty",
+        "dirtyShortRev": "3f9d287-dirty",
-        "lastModified": 1718529861,
+        "lastModified": 1720514984,
-        "narHash": "sha256-X1Wd6mDz8GTaoxt1ylkvZfrJOcZtspJrEjXMtJ2ZyG0=",
+        "narHash": "sha256-AuixwSlYk34Z6+GEc7y4QotF3Hk963zC9I9hAwX5KCE=",
         "type": "git",
         "url": "file:../?dir=lib"
       },

tidepool/src/builders/basic.nix

@@ -1,10 +1,8 @@
-{ lib, config }:
+{ config }:
 let
   cfg = config.builders.basic;
 
-  lib' = config.lib;
+  inherit (config) lib foundation;
-
-  inherit (config) foundation;
 in
 {
   config.builders = {
@@ -14,15 +12,46 @@ in
       build =
         package:
         let
-          phases = package.phases;
-          sorted = lib.dag.sort.topographic phases;
-
-          script = lib.strings.concatMapSep "\n" (
-            entry: if builtins.isFunction entry.value then entry.value package else entry.value
-          ) sorted.result;
-
           system = package.platform.build.double;
 
+          dependencies = lib.packages.dependencies.collect package;
+
+          context = lib.packages.context.create dependencies { };
+
+          hooks = lib.packages.hooks.create dependencies context;
+
+          phasesWithHooks =
+            let
+              all = lib.lists.flatten [
+                hooks.build.only
+                hooks.build.build
+                hooks.build.host
+                hooks.build.target
+                hooks.host.only
+                hooks.host.host
+                hooks.host.target
+                hooks.target.only
+                hooks.target.target
+              ];
+            in
+            builtins.foldl' (final: defaults: lib.dag.apply.defaults final defaults) package.phases all;
+
+          phases = lib.dag.apply.defaults phasesWithHooks {
+            unpack = lib.dag.entry.before [ "patch" ] "";
+
+            patch = lib.dag.entry.between [ "unpack" ] [ "configure" ] "";
+
+            configure = lib.dag.entry.between [ "patch" ] [ "build" ] "";
+
+            build = lib.dag.entry.between [ "configure" ] [ "install" ] "";
+
+            install = lib.dag.entry.after [ "build" ] "";
+          };
+
+          sorted = lib.dag.sort.topological phases;
+
+          script = lib.strings.concatMapSep "\n" (entry: entry.value) sorted.result;
+
           built = builtins.derivation (
             package.env
             // {
@@ -36,7 +65,7 @@ in
               PATH =
                 let
                   bins = lib.paths.bin (
-                    (lib'.packages.dependencies.getPackages package.deps.build.host)
+                    (lib.packages.dependencies.get dependencies.build.host)
                     ++ [
                       foundation.stage2-bash
                       foundation.stage2-coreutils
@@ -70,7 +99,14 @@ in
             }
           );
         in
-        built // { inherit (package) meta; };
+        built
+        // {
+          inherit (package) meta;
+          extras = {
+            inherit package context;
+            phases = builtins.listToAttrs sorted.result;
+          } // package.extras;
+        };
     };
   };
 }

tidepool/src/export.nix

@@ -1,18 +1,21 @@
 # This file handles creating all of the exports for this project and is not
 # exported itself.
-{ lib, config }:
+{ config }:
 let
-  lib' = config.lib;
+  inherit (config) lib;
 in
 {
-  freeform = lib.types.any;
+  # freeform = lib.types.any;
 
   config = {
     exports = {
-      lib = config.lib;
+      inherit lib;
       modules = import ./modules.nix;
 
       packages = {
+        aux-a = config.packages.aux.a;
+        aux-b = config.packages.aux.b;
+
         # foundation-gcc-x86_64 =
         # (config.packages.foundation.gcc.versions."13.2.0".extend (args: {
         #   config = {
@@ -24,11 +27,13 @@ in
         # .config;
         foundation-gcc = config.packages.foundation.gcc;
         foundation-binutils = config.packages.foundation.binutils;
-        foundation-linux-headers = config.packages.foundation.linux-headers.versions.latest.extend {
+        foundation-linux-headers = config.packages.foundation.linux-headers;
-          platform.host = lib.modules.overrides.force "x86_64-linux";
+        # foundation-linux-headers = config.packages.foundation.linux-headers.versions.latest.extend {
-        };
+        #   platform.host = lib.modules.overrides.force "x86_64-linux";
+        # };
         # example-x = config.packages.example.x;
-        # cross-example-x-x86_64-linux = config.packages.cross.x86_64-linux.example.x;
+        cross-aux-a-x86_64-linux = config.packages.cross.x86_64-linux.aux.a;
+        cross-foundation-gcc-x86_64-linux = config.packages.cross.x86_64-linux.foundation.gcc;
       };
     };
 

tidepool/src/lib/options.nix

@@ -5,7 +5,7 @@ in
   config = {
     lib.options = {
       package = lib.options.create {
-        type = config.lib.types.package;
+        type = config.lib.types.package.base;
         description = "A package definition.";
       };
     };

tidepool/src/lib/packages.nix

@@ -1,20 +1,272 @@
-{
+{ lib, config }:
-  lib,
+let
-  lib',
+  lib' = config.lib;
-  config,
+in
-}:
 {
   config = {
     lib.packages = {
       dependencies = {
-        getPackages =
+        get =
           dependencies:
           let
-            available = builtins.filter (dependency: !(builtins.isNull dependency)) (
+            exists = value: !(builtins.isNull value);
-              builtins.attrValues dependencies
+            available = builtins.filter exists dependencies;
-            );
           in
           builtins.map (dependency: dependency.package) available;
+
+        build =
+          build': host': target':
+          builtins.mapAttrs (name: dep: lib'.packages.build dep build' host' target');
+
+        collect =
+          package:
+          let
+            isPropagated = name: package: package.propagate or false;
+            getPropagatedDependencies = target: builtins.attrValues (lib.attrs.filter isPropagated target);
+
+            process =
+              dependencies:
+              let
+                getDeps =
+                  name: dependency:
+                  let
+                    deps = {
+                      build = {
+                        only = getPropagatedDependencies dependency.deps.build.only ++ process dependency.deps.build.only;
+                        build =
+                          getPropagatedDependencies dependency.deps.build.build
+                          ++ process dependency.deps.build.build;
+                        host = getPropagatedDependencies dependency.deps.build.host ++ process dependency.deps.build.host;
+                        target =
+                          getPropagatedDependencies dependency.deps.build.target
+                          ++ process dependency.deps.build.target;
+                      };
+                      host = {
+                        only = getPropagatedDependencies dependency.deps.host.only ++ process dependency.deps.host.only;
+                        host = getPropagatedDependencies dependency.deps.host.host ++ process dependency.deps.host.host;
+                        target =
+                          getPropagatedDependencies dependency.deps.host.target
+                          ++ process dependency.deps.host.target;
+                      };
+                      target = {
+                        only = getPropagatedDependencies dependency.deps.target.only ++ process dependency.deps.target.only;
+                        target =
+                          getPropagatedDependencies dependency.deps.target.target
+                          ++ process dependency.deps.target.target;
+                      };
+                    };
+                  in
+                  lib.lists.flatten [
+                    deps.build.only
+                    deps.build.build
+                    deps.build.host
+                    deps.build.target
+                    deps.host.only
+                    deps.host.host
+                    deps.host.target
+                    deps.target.only
+                    deps.target.target
+                  ];
+
+                propagated = lib.attrs.mapToList getDeps dependencies;
+              in
+              lib.lists.flatten propagated;
+          in
+          {
+            build = {
+              only = builtins.attrValues package.deps.build.only ++ process package.deps.build.only;
+              build = builtins.attrValues package.deps.build.build ++ process package.deps.build.build;
+              host = builtins.attrValues package.deps.build.host ++ process package.deps.build.host;
+              target = builtins.attrValues package.deps.build.target ++ process package.deps.build.target;
+            };
+            host = {
+              only = builtins.attrValues package.deps.host.only ++ process package.deps.host.only;
+              host = builtins.attrValues package.deps.host.host ++ process package.deps.host.host;
+              target = builtins.attrValues package.deps.host.target ++ process package.deps.host.target;
+            };
+            target = {
+              only = builtins.attrValues package.deps.target.only ++ process package.deps.target.only;
+              target = builtins.attrValues package.deps.target.target ++ process package.deps.target.target;
+            };
+          };
+      };
+
+      context = {
+        create =
+          collected: ctx:
+          let
+            process =
+              path:
+              let
+                dependencies = lib.attrs.selectOrThrow path collected;
+                contexts = builtins.map (dependency: dependency.context or { }) dependencies;
+                result = lib.modules.run {
+                  prefix = [ "<package>" ];
+                  modules = builtins.map (context: { config = context; }) contexts ++ [
+                    {
+                      freeform = lib.types.any;
+
+                      options = config.packages.context.options // {
+                        target = lib.options.create {
+                          description = "The dependency target that is being generated.";
+                          type = lib.types.enum [
+                            "build.only"
+                            "build.build"
+                            "build.host"
+                            "build.target"
+                            "host.only"
+                            "host.host"
+                            "host.target"
+                            "target.only"
+                            "target.target"
+                          ];
+                          writable = false;
+                          default.value = builtins.concatStringsSep "." path;
+                        };
+
+                        deps = lib.options.create {
+                          description = "The collected dependencies.";
+                          writable = false;
+                          default.value = collected;
+                          type = lib.types.submodule {
+                            options = {
+                              build = {
+                                only = lib.options.create { type = lib.types.list.of lib'.types.package; };
+                                build = lib.options.create { type = lib.types.list.of lib'.types.package; };
+                                host = lib.options.create { type = lib.types.list.of lib'.types.package; };
+                                target = lib.options.create { type = lib.types.list.of lib'.types.package; };
+                              };
+                              host = {
+                                only = lib.options.create { type = lib.types.list.of lib'.types.package; };
+                                host = lib.options.create { type = lib.types.list.of lib'.types.package; };
+                                target = lib.options.create { type = lib.types.list.of lib'.types.package; };
+                              };
+                              target = {
+                                only = lib.options.create { type = lib.types.list.of lib'.types.package; };
+                                target = lib.options.create { type = lib.types.list.of lib'.types.package; };
+                              };
+                            };
+                          };
+                        };
+                      };
+
+                      config = ctx;
+                    }
+                  ];
+                };
+              in
+              result.config;
+          in
+          {
+            build = {
+              only = process [
+                "build"
+                "only"
+              ];
+              build = process [
+                "build"
+                "build"
+              ];
+              host = process [
+                "build"
+                "host"
+              ];
+              target = process [
+                "build"
+                "target"
+              ];
+            };
+            host = {
+              only = process [
+                "host"
+                "only"
+              ];
+              host = process [
+                "host"
+                "host"
+              ];
+              target = process [
+                "host"
+                "target"
+              ];
+            };
+            target = {
+              only = process [
+                "target"
+                "only"
+              ];
+              target = process [
+                "target"
+                "target"
+              ];
+            };
+          };
+      };
+
+      hooks = {
+        create =
+          collected: ctx:
+          let
+            process =
+              path:
+              let
+                dependencies = lib.attrs.selectOrThrow path collected;
+                hooks = builtins.map
+                  (
+                    dependency:
+                    let
+                      getHooks = dependency.hooks or (lib.fp.const { });
+                    in
+                    getHooks ctx
+                  )
+                  dependencies;
+              in
+              hooks;
+          in
+          {
+            build = {
+              only = process [
+                "build"
+                "only"
+              ];
+              build = process [
+                "build"
+                "build"
+              ];
+              host = process [
+                "build"
+                "host"
+              ];
+              target = process [
+                "build"
+                "target"
+              ];
+            };
+            host = {
+              only = process [
+                "host"
+                "only"
+              ];
+              host = process [
+                "host"
+                "host"
+              ];
+              target = process [
+                "host"
+                "target"
+              ];
+            };
+            target = {
+              only = process [
+                "target"
+                "only"
+              ];
+              target = process [
+                "target"
+                "target"
+              ];
+            };
+          };
       };
 
       getLatest =
@@ -25,54 +277,89 @@
         in
         builtins.head sorted;
 
-      build =
+      resolve =
-        package: build: host: target:
+        alias:
-        let
+        if alias ? versions then
-          resolved =
+          alias.versions.${config.preferences.packages.version}
-            if package ? versions then
+            or (alias.versions.${lib'.packages.getLatest alias})
-              package.versions.${config.preferences.packages.version}
-                or (package.versions.${lib'.packages.getLatest package})
         else
-              package;
+          alias;
+
+      build =
+        alias: build: host: target:
+        let
+          package = lib'.packages.resolve alias;
 
           buildDependencies =
             build': host': target':
             builtins.mapAttrs (name: dep: lib'.packages.build dep build' host' target');
 
-          result = resolved.extend (
+          platform = {
+            build = lib.modules.overrides.force build;
+            host = lib.modules.overrides.force host;
+            target = lib.modules.overrides.force target;
+          };
+
+          withPlatform = lib.modules.run {
+            modules = package.__modules__ ++ [
+              lib'.types.package.children.submodule
+              (
                 { config }:
                 {
                   config = {
-                platform = {
+                    __modules__ = package.__modules__;
-                  build = build;
+
-                  host = host;
+                    inherit platform;
-                  target = lib.modules.override 150 target;
+                  };
+                }
+              )
+            ];
           };
 
+          # Not all platform information can be effectively handled via submodules. To handle
+          # the case where a user copies the resolved config over we need to ensure that
+          # dependencies are appropriately updated.
+          withDeps = withPlatform.config // {
             deps = {
               build = {
-                    only = buildDependencies build build build resolved.deps.build.only;
+                only = buildDependencies build build build withPlatform.config.deps.build.only;
-                    build = buildDependencies build build target resolved.deps.build.build;
+                build = buildDependencies build build target withPlatform.config.deps.build.build;
-                    host = buildDependencies build host target resolved.deps.build.host;
+                host = buildDependencies build host target withPlatform.config.deps.build.host;
-                    target = buildDependencies build target target resolved.deps.build.target;
+                target = buildDependencies build target target withPlatform.config.deps.build.target;
               };
               host = {
-                    only = buildDependencies host host host resolved.deps.host.only;
+                only = buildDependencies host host host withPlatform.config.deps.host.only;
-                    host = buildDependencies host host target resolved.deps.host.host;
+                host = buildDependencies host host target withPlatform.config.deps.host.host;
-                    target = buildDependencies host target target resolved.deps.host.target;
+                target = buildDependencies host target target withPlatform.config.deps.host.target;
               };
               target = {
-                    only = buildDependencies target target target resolved.deps.target.only;
+                only = buildDependencies target target target withPlatform.config.deps.target.only;
-                    target = buildDependencies target target target resolved.deps.target.target;
+                target = buildDependencies target target target withPlatform.config.deps.target.target;
+              };
             };
           };
 
-                package = config.builder.build config;
+          withPackage = lib.modules.run {
+            modules = package.__modules__ ++ [
+              lib'.types.package.children.submodule
+              (
+                { config }:
+                {
+                  config = {
+                    __modules__ = package.__modules__;
+
+                    inherit platform;
+
+                    deps = lib.modules.overrides.force withDeps.deps;
+
+                    package = lib.modules.overrides.force (withDeps.builder.build withDeps);
                   };
                 }
-          );
+              )
+            ];
+          };
         in
-        result;
+        withPackage.config;
     };
   };
 }

tidepool/src/lib/systems.nix

@@ -1220,6 +1220,7 @@ in
               vendor,
               kernel,
               abi,
+              ...
             }:
             types.cpu.check cpu
             && types.vendor.check vendor
@@ -1227,6 +1228,17 @@ in
             && types.abi.check abi;
         };
 
+        platformWithBuildInfo = lib.types.create {
+          name = "systemWithBuildInfo";
+          description = "fully parsed representation of llvm- or nix-style platform tuple with build information";
+          merge = lib.options.merge.one;
+          check =
+            value:
+            lib.types.is "systemWithBuildInfo" value
+            && value ? system
+            && lib'.systems.types.platform.check value.system;
+        };
+
         endian = lib.types.enum (builtins.attrValues types.endians);
 
         endians = setTypes types.generic.endian {
@@ -2792,7 +2804,7 @@ in
         assert resolved.useAndroidPrebuilt -> resolved.isAndroid;
         assert assertions;
         # And finally, return the generated system info.
-        resolved;
+        lib.types.set "systemWithBuildInfo" resolved;
     };
   };
 }

tidepool/src/lib/types.nix

@@ -1,8 +1,9 @@
-{
+{ lib, config }:
-  lib,
+let
-  lib',
+  inherit (config) preferences builders;
-  config,
+
-}:
+  lib' = config.lib;
+in
 {
   config = {
     lib.types = {
@@ -55,6 +56,10 @@
         in
         lib.types.either type (lib.types.list.of type);
 
+      platform =
+        lib.types.coerce lib.types.string lib'.systems.withBuildInfo
+          lib'.systems.types.platformWithBuildInfo;
+
       builder = lib.types.submodule {
         freeform = lib.types.any;
 
@@ -66,60 +71,191 @@
         };
       };
 
-      packages = lib.types.attrs.of (lib'.types.alias);
+      packages = lib.types.attrs.of (lib.types.attrs.of lib'.types.alias);
 
-      alias = lib.types.attrs.of (
+      dependencies =
-        lib.types.submodule {
+        build: host: target:
-          options = {
+        let
-            versions = lib.options.create {
+          initial = lib.types.raw;
-              description = "All available package versions.";
-              type = lib.types.attrs.of lib'.types.package;
-            };
-          };
-        }
-      );
 
-      dependencies = lib.types.attrs.of (
+          transform =
-        lib.types.nullish (lib.types.either lib'.types.alias lib'.types.package)
-      );
-
-      package = lib.types.submodule (
-        { config, meta }:
-        {
-          options = {
-            extend = lib.options.create {
-              description = "Extend the package's submodules with additional configuration.";
-              type = lib.types.function lib.types.raw;
-              default.value =
             value:
             let
-                  result = meta.extend {
+              package = lib'.packages.resolve value;
-                    modules = if builtins.isAttrs value then [ { config = value; } ] else lib.lists.from.any value;
+            in
+            lib'.packages.build package build host target;
+        in
+        lib.types.attrs.of (lib.types.coerce initial transform lib'.types.package);
+
+      alias = lib.types.submodule {
+        options = {
+          stable = lib.options.create {
+            description = "The stable version of the package.";
+            type = lib.types.nullish lib'.types.package;
+          };
+
+          latest = lib.options.create {
+            description = "The latest version of the package.";
+            type = lib'.types.package;
+          };
+
+          versions = lib.options.create {
+            description = "Available versions of the package.";
+            type = lib.types.attrs.of lib'.types.package;
+            default.value = { };
+          };
+        };
+      };
+
+      package =
+        let
+          normalize =
+            value:
+            if builtins.isFunction value || builtins.isList value then
+              value
+            else if value ? __modules__ then
+              value.__modules__
+            else
+              { config = value; };
+
+          initial = lib.types.create {
+            name = "PackageConfig";
+            description = "configuration for a package";
+            check = value: builtins.isFunction value || builtins.isAttrs value || builtins.isList value;
+            merge =
+              location: definitions:
+              let
+                normalized = builtins.map (definition: lib.lists.from.any (normalize definition.value)) definitions;
+              in
+              builtins.concatLists normalized;
+          };
+
+          transform =
+            location: value:
+            let
+              modules = lib.lists.from.any (normalize value);
+
+              result = lib.modules.run {
+                prefix = location;
+                modules = modules ++ [
+                  submodule
+                  { config.__modules__ = modules; }
+                ];
               };
             in
             result.config;
+
+          final = lib.types.raw;
+
+          deps =
+            build: host: target:
+            lib.types.submodule {
+              options = {
+                build = {
+                  only = lib.options.create {
+                    description = "Dependencies which are only used in the build environment.";
+                    type = lib'.types.dependencies build build build;
+                    default.value = { };
                   };
 
-            name = lib.options.create {
+                  build = lib.options.create {
-              description = "The name of the package.";
+                    description = "Dependencies which are created in the build environment and are executed in the build environment.";
-              type = lib.types.string;
+                    type = lib'.types.dependencies build build target;
-              default = {
+                    default.value = { };
-                text = "\${config.pname}-\${config.version}";
+                  };
-                value =
+
-                  if config.pname != null && config.version != null then "${config.pname}-${config.version}" else "";
+                  host = lib.options.create {
+                    description = "Dependencies which are created in the build environment and are executed in the host environment.";
+                    type = lib'.types.dependencies build host target;
+                    default.value = { };
+                  };
+
+                  target = lib.options.create {
+                    description = "Dependencies which are created in the build environment and are executed in the target environment.";
+                    type = lib'.types.dependencies build target target;
+                    default.value = { };
                   };
                 };
 
-            pname = lib.options.create {
+                host = {
-              description = "The program name for the package";
+                  only = lib.options.create {
-              type = lib.types.nullish lib.types.string;
+                    description = "Dependencies which are only used in the host environment.";
-              default.value = null;
+                    type = lib'.types.dependencies host host host;
+                    default.value = { };
                   };
 
-            version = lib.options.create {
+                  host = lib.options.create {
-              description = "The version for the package.";
+                    description = "Dependencies which are executed in the host environment.";
-              type = lib.types.nullish lib.types.version;
+                    type = lib'.types.dependencies host host target;
-              default.value = null;
+                    default.value = { };
+                  };
+
+                  target = lib.options.create {
+                    description = "Dependencies which are executed in the host environment which produces code for the target environment.";
+                    type = lib'.types.dependencies host target target;
+                    default.value = { };
+                  };
+                };
+
+                target = {
+                  only = lib.options.create {
+                    description = "Dependencies which are only used in the target environment.";
+                    type = lib'.types.dependencies target target target;
+                    default.value = { };
+                  };
+
+                  target = lib.options.create {
+                    description = "Dependencies which are executed in the target environment.";
+                    type = lib'.types.dependencies target target target;
+                    default.value = { };
+                  };
+                };
+              };
+            };
+
+          submodule =
+            { config, meta }:
+            let
+              build = config.platform.build;
+              host = config.platform.host;
+              target = config.platform.target;
+            in
+            {
+              options = {
+                __modules__ = lib.options.create {
+                  description = "User specified modules for the package definition.";
+                  type = lib.types.list.of (initial // { merge = lib.options.merge.one; });
+                  # writable = false;
+                  internal = true;
+                  default.value = [ ];
+                };
+
+                extend = lib.options.create {
+                  description = "Extend the package definition.";
+                  type = lib.types.function lib.types.raw;
+                  internal = true;
+                  writable = false;
+                  default.value = module:
+                    let
+                      normalized =
+                        if builtins.isList module then
+                          module
+                        else if builtins.isFunction module || module ? config then
+                          [ module ]
+                        else
+                          [{
+                            config = module;
+                          }];
+                      result = meta.extend {
+                        modules =
+                          normalized ++ [
+                            {
+                              config.__modules__ = lib.modules.overrides.force (config.__modules__ ++ normalized);
+                            }
+                          ];
+                      };
+                    in
+                    result.config;
                 };
 
                 meta = {
@@ -172,67 +308,57 @@
                   };
                 };
 
+                extras = lib.options.create {
+                  description = "Extra information for the package.";
+                  type = lib.types.attrs.of lib.types.any;
+                  default.value = { };
+                };
+
                 platform = {
                   build = lib.options.create {
                     description = "The build platform for the package.";
-                type = lib.types.string;
+                    type = lib'.types.platform;
-                default.value = "x86_64-linux";
+                    default.value = lib'.systems.withBuildInfo "x86_64-linux";
-                apply =
-                  raw:
-                  let
-                    system = lib'.systems.from.string raw;
-                    x = lib'.systems.withBuildInfo raw;
-                  in
-                  x;
                   };
 
                   host = lib.options.create {
                     description = "The host platform for the package.";
-                type = lib.types.string;
+                    type = lib'.types.platform;
-                default.value = "x86_64-linux";
+                    default.value = lib'.systems.withBuildInfo "x86_64-linux";
-                # apply = raw: let
-                #   system = lib'.systems.from.string raw;
-                # in {
-                #   inherit raw system;
-
-                #   double = lib'.systems.into.double system;
-                #   triple = lib'.systems.into.triple system;
-                # };
-                apply =
-                  raw:
-                  let
-                    system = lib'.systems.from.string raw;
-                    x = lib'.systems.withBuildInfo raw;
-                  in
-                  x;
                   };
 
                   target = lib.options.create {
                     description = "The target platform for the package.";
+                    type = lib'.types.platform;
+                    default.value = lib'.systems.withBuildInfo "x86_64-linux";
+                  };
+                };
+
+                name = lib.options.create {
+                  description = "The name of the package.";
                   type = lib.types.string;
-                default.value = "x86_64-linux";
+                  default = {
-                # apply = raw: let
+                    text = "\${config.pname}-\${config.version}";
-                #   system = lib'.systems.from.string raw;
+                    value =
-                # in {
+                      if config.pname != null && config.version != null then "${config.pname}-${config.version}" else "";
-                #   inherit raw system;
-
-                #   double = lib'.systems.into.double system;
-                #   triple = lib'.systems.into.triple system;
-                # };
-                apply =
-                  raw:
-                  let
-                    system = lib'.systems.from.string raw;
-                    x = lib'.systems.withBuildInfo raw;
-                  in
-                  x;
                   };
                 };
 
-            phases = lib.options.create {
+                pname = lib.options.create {
-              description = "The phases for the package.";
+                  description = "The program name for the package";
-              type = lib.types.dag.of (lib.types.either lib.types.string (lib.types.function lib.types.string));
+                  type = lib.types.nullish lib.types.string;
-              default.value = { };
+                  default.value = null;
+                };
+
+                version = lib.options.create {
+                  description = "The version for the package.";
+                  type = lib.types.nullish lib.types.version;
+                  default.value = null;
+                };
+
+                builder = lib.options.create {
+                  description = "The builder for the package.";
+                  type = lib'.types.builder;
                 };
 
                 env = lib.options.create {
@@ -241,81 +367,72 @@
                   default.value = { };
                 };
 
-            builder = lib.options.create {
-              description = "The builder for the package.";
-              type = lib'.types.builder;
-            };
-
-            deps = {
-              build = {
-                only = lib.options.create {
-                  description = "Dependencies which are only used in the build environment.";
-                  type = lib'.types.dependencies;
-                  default.value = { };
-                };
-
-                build = lib.options.create {
-                  description = "Dependencies which are created in the build environment and are executed in the build environment.";
-                  type = lib'.types.dependencies;
-                  default.value = { };
-                };
-
-                host = lib.options.create {
-                  description = "Dependencies which are created in the build environment and are executed in the host environment.";
-                  type = lib'.types.dependencies;
-                  default.value = { };
-                };
-
-                target = lib.options.create {
-                  description = "Dependencies which are created in the build environment and are executed in the target environment.";
-                  type = lib'.types.dependencies;
-                  default.value = { };
-                };
-              };
-
-              host = {
-                only = lib.options.create {
-                  description = "Dependencies which are only used in the host environment.";
-                  type = lib'.types.dependencies;
-                  default.value = { };
-                };
-
-                host = lib.options.create {
-                  description = "Dependencies which are executed in the host environment.";
-                  type = lib'.types.dependencies;
-                  default.value = { };
-                };
-
-                target = lib.options.create {
-                  description = "Dependencies which are executed in the host environment which produces code for the target environment.";
-                  type = lib'.types.dependencies;
-                  default.value = { };
-                };
-              };
-
-              target = {
-                only = lib.options.create {
-                  description = "Dependencies which are only used in the target environment.";
-                  type = lib'.types.dependencies;
-                  default.value = { };
-                };
-
-                target = lib.options.create {
-                  description = "Dependencies which are executed in the target environment.";
-                  type = lib'.types.dependencies;
-                  default.value = { };
-                };
-              };
-            };
-
                 package = lib.options.create {
                   description = "The built derivation.";
                   type = lib.types.derivation;
                   default.value = config.builder.build config;
                 };
+
+                phases = lib.options.create {
+                  description = "The phases for the package.";
+                  type = lib.types.dag.of lib.types.string;
+                  default.value = { };
+                };
+
+                context = lib.options.create {
+                  description = "The context information that the package provides.";
+                  type = lib.types.attrs.of lib.types.raw;
+                  default.value = { };
+                };
+
+                hooks = lib.options.create {
+                  description = "The hooks that the package provides.";
+                  type = lib.types.function (lib.types.dag.of lib.types.string);
+                  default.value = ctx: { };
+                };
+
+                propagate = lib.options.create {
+                  description = "Whether the package should propagate its hooks and context.";
+                  type = lib.types.bool;
+                  default.value = false;
+                };
+
+                deps = lib.options.create {
+                  description = "The dependencies for the package.";
+                  type = deps build host target;
+                  default.value = { };
+                  apply = value: {
+                    build = {
+                      only = lib'.packages.dependencies.build build build build value.build.only;
+                      build = lib'.packages.dependencies.build build build target value.build.build;
+                      host = lib'.packages.dependencies.build build host target value.build.host;
+                      target = lib'.packages.dependencies.build build target target value.build.target;
+                    };
+                    host = {
+                      only = lib'.packages.dependencies.build host host host value.host.only;
+                      host = lib'.packages.dependencies.build host host target value.host.host;
+                      target = lib'.packages.dependencies.build host target target value.host.target;
+                    };
+                    target = {
+                      only = lib'.packages.dependencies.build target target target value.target.only;
+                      target = lib'.packages.dependencies.build target target target value.target.target;
+                    };
+                  };
+                };
+              };
+            };
+
+          type = (lib.types.coerceWithLocation initial transform final) // {
+            name = "Package";
+            description = "a package definition";
+          };
+        in
+        type
+        // {
+          children = type.children // {
+            inherit submodule;
+          };
         };
-        }
-      );
     };
   };
 }

tidepool/src/packages/aux/a.nix

@@ -0,0 +1,36 @@
+{ lib', config }:
+let
+  inherit (config) builders packages;
+in
+{
+  config.packages.aux.a = {
+    versions = {
+      "latest" =
+        { config }:
+        {
+          config = {
+            meta = {
+              platforms = [ "i686-linux" ];
+            };
+
+            name = "${config.pname}-${config.version}";
+
+            pname = "a";
+            version = "1.0.0";
+
+            builder = builders.basic;
+
+            deps.build.host = {
+              inherit (packages.aux) b;
+            };
+
+            phases = {
+              install = ''
+                echo "a with b: ${config.deps.build.host.b.package.system}" > $out
+              '';
+            };
+          };
+        };
+    };
+  };
+}

tidepool/src/packages/aux/b.nix

@@ -0,0 +1,54 @@
+{ config }:
+let
+  inherit (config) lib builders packages;
+in
+{
+  config.packages.aux.b = {
+    versions = {
+      "latest" =
+        { config }:
+        {
+          options = {
+            custom = lib.options.create { type = lib.types.bool; };
+          };
+
+          config = {
+            meta = {
+              platforms = [ "i686-linux" ];
+            };
+
+            name = "${config.pname}-${config.version}";
+
+            custom = true;
+
+            pname = "b";
+            version = "1.0.0";
+
+            builder = builders.basic;
+
+            deps = {
+              build = {
+                host = {
+                  c = packages.aux.c.versions.latest.extend {
+                    propagate = true;
+                  };
+                };
+              };
+            };
+
+            context = {
+              "foundation:cflags" = [ "-I $AUX_B/include" ];
+            };
+
+            hooks = ctx: { "aux:b:env" = lib.dag.entry.after [ "unpack" ] ''export AUX_B=${config.package}''; };
+
+            phases = {
+              install = ''
+                echo "b" > $out
+              '';
+            };
+          };
+        };
+    };
+  };
+}

tidepool/src/packages/aux/c.nix

@@ -0,0 +1,44 @@
+{ config }:
+let
+  inherit (config) lib builders packages;
+in
+{
+  config.packages.aux.c = {
+    versions = {
+      "latest" =
+        { config }:
+        {
+          options = {
+            custom = lib.options.create { type = lib.types.bool; };
+          };
+
+          config = {
+            meta = {
+              platforms = [ "i686-linux" ];
+            };
+
+            name = "${config.pname}-${config.version}";
+
+            custom = true;
+
+            pname = "c";
+            version = "1.0.0";
+
+            builder = builders.basic;
+
+            context = {
+              "foundation:cflags" = [ "-I $AUX_C/include" ];
+            };
+
+            hooks = ctx: { "aux:c:env" = lib.dag.entry.after [ "unpack" ] ''export AUX_C=${config.package}''; };
+
+            phases = {
+              install = ''
+                echo "c" > $out
+              '';
+            };
+          };
+        };
+    };
+  };
+}

tidepool/src/packages/default.nix

@@ -1,30 +1,43 @@
-{
+{ config }:
-  lib,
-  lib',
-  config,
-}:
 let
-  doubles = lib'.systems.doubles.all;
+  inherit (config) lib;
+
+  doubles = lib.systems.doubles.all;
 
   packages = builtins.removeAttrs config.packages [ "cross" ];
 in
 {
-  includes = [ ./foundation ];
+  includes = [
+    ./foundation
+    ./aux/a.nix
+    ./aux/b.nix
+    ./aux/c.nix
+  ];
 
   options = {
     packages = lib.options.create {
       description = "The package set.";
       type = lib.types.submodule {
-        freeform = lib.types.attrs.of (lib.types.submodule { freeform = lib'.types.alias; });
+        freeform = lib.types.packages;
 
-        options.cross = lib.attrs.generate doubles (
+        options = {
+          cross = lib.attrs.generate doubles (
             system:
             lib.options.create {
               description = "The cross-compiled package set for the ${system} target.";
-            type = lib'.types.packages;
+              type = lib.types.packages;
-            default = { };
+              default.value = { };
             }
           );
+
+          # NOTE: We may offer a way to set default context values. For this reason we have
+          # nested `options` under `context` rather than using a plain option directly under `packages`.
+          context.options = lib.options.create {
+            description = "The available options for package contexts.";
+            default.value = { };
+            type = lib.types.attrs.of lib.types.option;
+          };
+        };
       };
     };
 
@@ -40,47 +53,28 @@ in
     };
   };
 
-  config.packages.cross = lib.attrs.generate doubles (
+  config = {
+    packages.cross = lib.attrs.generate doubles (
       system:
-    builtins.mapAttrs (
+      builtins.mapAttrs
+        (
           namespace:
           builtins.mapAttrs (
             name: alias:
               let
                 setHost =
                   package:
-            if package != { } then
+                  package
-              (package.extend (
+                  // {
-                { config }:
+                    __modules__ = package.__modules__ ++ [
                       {
-                  config = {
+                        config.platform = {
-                    platform = {
+                          host = lib.modules.override 5 system;
-                      host = lib.modules.overrides.force system;
+                          target = lib.modules.override 5 system;
-                      target = lib.modules.overrides.default system;
-                    };
-
-                    deps = {
-                      build = {
-                        only = setHost package.deps.build.only;
-                        build = setHost package.deps.build.build;
-                        host = setHost package.deps.build.host;
-                        target = setHost package.deps.build.target;
-                      };
-                      host = {
-                        only = setHost package.deps.host.only;
-                        host = setHost package.deps.host.host;
-                        target = setHost package.deps.host.target;
-                      };
-                      target = {
-                        only = setHost package.deps.target.only;
-                        target = setHost package.deps.target.target;
-                      };
-                    };
                         };
                       }
-              )).config
+                    ];
-            else
+                  };
-              package;
 
                 updated = alias // {
                   versions = builtins.mapAttrs (version: package: setHost package) alias.versions;
@@ -88,6 +82,8 @@ in
               in
               updated
           )
-    ) packages
+        )
+        packages
     );
+  };
 }

tidepool/src/packages/foundation/binutils/default.nix

@@ -11,13 +11,14 @@ let
     # These are the upstream foundational packages exported from the Aux Foundation project.
 
     foundation
+    packages
     ;
 in
 {
   config.packages.foundation.binutils = {
     versions = {
       "latest" =
-        { config, meta }:
+        { config }:
         {
           options = {
             src = lib.options.create {
@@ -36,9 +37,17 @@ in
 
             builder = builders.basic;
 
+            deps = {
+              build = {
+                host = {
+                  inherit (packages.foundation) gcc;
+                };
+              };
+            };
+
             env = {
               PATH = lib.paths.bin [
-                foundation.stage2-gcc
+                # foundation.stage2-gcc
                 foundation.stage2-binutils
                 foundation.stage2-gnumake
                 foundation.stage2-gnupatch
@@ -86,24 +95,24 @@ in
                 ];
               in
               {
-                unpack = lib.dag.entry.before [ "patch" ] ''
+                unpack = ''
                   tar xf ${config.src}
                   cd binutils-${config.version}
                 '';
 
-                patch = lib.dag.entry.between [ "configure" ] [ "unpack" ] ''
+                patch = ''
                   ${lib.strings.concatMapSep "\n" (file: "patch -Np1 -i ${file}") patches}
                 '';
 
-                configure = lib.dag.entry.between [ "build" ] [ "patch" ] ''
+                configure = ''
                   bash ./configure ${builtins.concatStringsSep " " configureFlags}
                 '';
 
-                build = lib.dag.entry.between [ "install" ] [ "configure" ] ''
+                build = ''
                   make -j $NIX_BUILD_CORES
                 '';
 
-                install = lib.dag.entry.after [ "build" ] ''
+                install = ''
                   make -j $NIX_BUILD_CORES install-strip
                 '';
               };

tidepool/src/packages/foundation/default.nix

@@ -9,6 +9,8 @@
     ./gcc
     ./binutils
     ./linux-headers
+    ./glibc
+    # ./xz
   ];
 
   config = {

tidepool/src/packages/foundation/gcc/default.nix

@@ -1,19 +1,23 @@
-{
+{ config, options }:
-  lib,
-  lib',
-  config,
-  options,
-}:
 let
   inherit (config)
+    lib
     mirrors
     builders
     # These are the upstream foundational packages exported from the Aux Foundation project.
 
     foundation
+    packages
     ;
 in
 {
+  config.packages.context.options = {
+    "foundation:cflags" = lib.options.create {
+      type = lib.types.list.of lib.types.string;
+      default.value = [ ];
+    };
+  };
+
   config.packages.foundation.gcc = {
     versions = {
       "latest" =
@@ -91,28 +95,7 @@ in
             builder = builders.basic;
 
             env = {
-              PATH =
+              PATH = lib.paths.bin [
-                let
-                  gcc =
-                    if
-                      config.platform.build.triple == config.platform.host.triple
-                    # If we're on the same system then we can use the existing GCC instance.
-                    then
-                      foundation.stage2-gcc
-                    # Otherwise we are going to need a cross-compiler.
-                    else
-                      # TODO: Create a gcc-cross package.
-                      (meta.extend (args: {
-                        config = {
-                          platform = {
-                            build = config.platform.build.triple;
-                            host = config.platform.build.triple;
-                            target = lib.modules.override.force config.platform.host.triple;
-                          };
-                        };
-                      })).config.package;
-                in
-                lib.paths.bin [
                 foundation.stage2-gcc
                 foundation.stage2-binutils
                 foundation.stage2-gnumake
@@ -130,12 +113,12 @@ in
 
             phases =
               let
-                host = lib'.systems.withBuildInfo config.platform.host;
+                host = lib.systems.withBuildInfo config.platform.host;
 
                 mbits = if host.system.cpu.family == "x86" then if host.is64bit then "-m64" else "-m32" else "";
               in
               {
-                unpack = lib.dag.entry.before [ "patch" ] ''
+                unpack = ''
                   # Unpack
                   tar xf ${config.src}
                   tar xf ${config.gmp.src}
@@ -150,17 +133,15 @@ in
                   ln -s ../isl-${config.isl.version} isl
                 '';
 
-                patch = lib.dag.entry.between [ "configure" ] [ "unpack" ] ''
+                patch = ''
                   # Patch
                   # force musl even if host triple is gnu
                   sed -i 's|"os/gnu-linux"|"os/generic"|' libstdc++-v3/configure.host
                 '';
 
-                configure = lib.dag.entry.between [ "build" ] [ "patch" ] ''
+                configure = ''
                   # Configure
-                  export CC="gcc -Wl,-dynamic-linker -march=${
+                  export CC="gcc -Wl,-dynamic-linker -Wl,${foundation.stage1-musl}/lib/libc.so"
-                    host.gcc.arch or host.system.cpu.family
-                  } ${mbits} -Wl,${foundation.stage1-musl}/lib/libc.so"
                   export CXX="g++ -Wl,-dynamic-linker -Wl,${foundation.stage1-musl}/lib/libc.so"
                   export CFLAGS_FOR_TARGET="-Wl,-dynamic-linker -Wl,${foundation.stage1-musl}/lib/libc.so"
                   export LIBRARY_PATH="${foundation.stage1-musl}/lib"
@@ -182,12 +163,12 @@ in
                     CXXFLAGS=-static
                 '';
 
-                build = lib.dag.entry.between [ "install" ] [ "configure" ] ''
+                build = ''
                   # Build
                   make -j $NIX_BUILD_CORES
                 '';
 
-                install = lib.dag.entry.after [ "build" ] ''
+                install = ''
                   # Install
                   make -j $NIX_BUILD_CORES install-strip
                 '';

tidepool/src/packages/foundation/glibc/default.nix

@@ -79,12 +79,12 @@ in
             };
 
             phases = {
-              unpack = lib.dag.entry.before [ "patch" ] ''
+              unpack = ''
                 tar xf ${config.src}
                 cd glibc-${config.version}
               '';
 
-              configure = lib.dag.entry.between [ "build" ] [ "patch" ] ''
+              configure = ''
                 mkdir build
                 cd build
                 # libstdc++.so is built against musl and fails to link
@@ -96,12 +96,12 @@ in
                   --with-headers=${foundation.stage1-linux-headers}/include
               '';
 
-              build = lib.dag.entry.between [ "install" ] [ "configure" ] ''
+              build = ''
                 # Build
                 make -j $NIX_BUILD_CORES
               '';
 
-              install = lib.dag.entry.after [ "build" ] ''
+              install = ''
                 # Install
                 make -j $NIX_BUILD_CORES install-strip
               '';

tidepool/src/packages/foundation/linux-headers/default.nix

@@ -54,20 +54,16 @@ in
             };
 
             phases = {
-              unpack = lib.dag.entry.before [ "patch" ] ''
+              unpack = ''
                 tar xf ${config.src}
                 cd linux-${config.version}
               '';
 
-              patch = lib.dag.entry.between [ "configure" ] [ "unpack" ] '''';
+              build = ''
-
-              configure = lib.dag.entry.between [ "build" ] [ "patch" ] '''';
-
-              build = lib.dag.entry.between [ "install" ] [ "configure" ] ''
                 make -j $NIX_BUILD_CORES CC=musl-gcc HOSTCC=musl-gcc ARCH=${config.platform.host.linux.arch} headers
               '';
 
-              install = lib.dag.entry.after [ "build" ] ''
+              install = ''
                 find usr/include -name '.*' -exec rm {} +
                 mkdir -p $out
                 cp -rv usr/include $out/