145 lines
4.9 KiB
Nix
145 lines
4.9 KiB
Nix
lib: {
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generators = {
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## Limit evaluation of a valud to a certain depth.
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##
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## @type { limit? :: Int | Null, throw? :: Bool } -> a -> a
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withRecursion = {
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limit ? null,
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throw ? true,
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}:
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assert builtins.isInt limit; let
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special = [
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"__functor"
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"__functionArgs"
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"__toString"
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"__pretty__"
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];
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attr = next: name:
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if builtins.elem name special
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then lib.fp.id
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else next;
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transform = depth:
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if limit != null && depth > limit
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then
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if throw
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then builtins.throw "Exceeded maximum eval-depth limit of ${builtins.toString limit} while trying to evaluate with `lib.generators.withRecursion'!"
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else lib.fp.const "<unevaluated>"
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else lib.fp.id;
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process = depth: value: let
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next = x: process (depth + 1) (transform (depth + 1) x);
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in
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if builtins.isAttrs value
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then builtins.mapAttrs (attr next) value
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else if builtins.isList value
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then builtins.map next value
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else transform (depth + 1) value;
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in
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process 0;
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## Create a pretty printer for Nix values.
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##
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## @type { indent? :: String, multiline? :: Bool, allowCustomPrettifiers? :: Bool } -> a -> string
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pretty = {
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indent ? "",
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multiline ? true,
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allowCustomPrettifiers ? false,
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}: let
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process = indent: value: let
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prefix =
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if multiline
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then "\n${indent} "
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else " ";
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suffix =
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if multiline
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then "\n${indent}"
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else " ";
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prettyNull = "null";
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prettyNumber = lib.numbers.into.string value;
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prettyBool = lib.bools.into.string value;
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prettyPath = builtins.toString value;
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prettyString = let
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lines = builtins.filter (x: !builtins.isList x) (builtins.split "\n" value);
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escapeSingleline = lib.strings.escape.any ["\\" "\"" "\${"];
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escapeMultiline = builtins.replaceStrings ["\${" "''"] ["''\${" "'''"];
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singlelineResult = "\"" + lib.strings.concatMapSep "\\n" escapeSingleline lines + "\"";
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multilineResult = let
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escapedLines = builtins.map escapeMultiline lines;
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# The last line gets a special treatment: if it's empty, '' is on its own line at the "outer"
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# indentation level. Otherwise, '' is appended to the last line.
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lastLine = lib.last escapedLines;
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contents = builtins.concatStringsSep prefix (lib.lists.init escapedLines);
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contentsSuffix =
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if lastLine == ""
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then suffix
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else prefix + lastLine;
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in
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"''"
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+ prefix
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+ contents
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+ contentsSuffix
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+ "''";
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in
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if multiline && builtins.length lines > 1
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then multilineResult
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else singlelineResult;
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prettyList = let
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contents = lib.strings.concatMapSep prefix (process (indent + " ")) value;
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in
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if builtins.length value == 0
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then "[ ]"
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else "[${prefix}${contents}${suffix}]";
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prettyFunction = let
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args = lib.fp.args value;
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markArgOptional = name: default:
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if default
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then name + "?"
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else name;
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argsWithDefaults = lib.attrs.mapToList markArgOptional args;
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serializedArgs = builtins.concatStringsSep ", " argsWithDefaults;
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in
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if args == {}
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then "<function>"
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else "<function, args: {${serializedArgs}}>";
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prettyAttrs = let
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contents = builtins.concatStringsSep prefix (lib.attrs.mapToList
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(name: value: "${lib.strings.escape.nix.identifier name} = ${
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builtins.addErrorContext "while evaluating an attribute `${name}`"
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(process (indent + " ") value)
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};")
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value);
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in
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if allowCustomPrettifiers && value ? __pretty__ && value ? value
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then value.__pretty__ value.value
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else if value == {}
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then "{ }"
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else if lib.packages.isDerivation value
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then "<derivation ${value.name or "???"}>"
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else "{${prefix}${contents}${suffix}}";
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in
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if null == value
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then prettyNull
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else if builtins.isInt value || builtins.isFloat value
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then prettyNumber
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else if builtins.isBool value
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then prettyBool
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else if builtins.isString value
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then prettyString
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else if builtins.isPath value
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then prettyPath
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else if builtins.isList value
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then prettyList
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else if builtins.isFunction value
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then prettyFunction
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else if builtins.isAttrs value
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then prettyAttrs
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else builtins.abort "lib.generators.pretty: should never happen (value = ${value})";
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in
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process indent;
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};
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}
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