core/lib/filesystem.nix

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/*
Functions for querying information about the filesystem
without copying any files to the Nix store.
*/
{ lib }:
# Tested in lib/tests/filesystem.sh
let
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inherit (builtins) readDir pathExists toString;
inherit (lib.attrsets) mapAttrs' filterAttrs;
inherit (lib.filesystem) pathType;
inherit (lib.strings) hasSuffix removeSuffix;
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in
{
/*
The type of a path. The path needs to exist and be accessible.
The result is either "directory" for a directory, "regular" for a regular file, "symlink" for a symlink, or "unknown" for anything else.
Type:
pathType :: Path -> String
Example:
pathType /.
=> "directory"
pathType /some/file.nix
=> "regular"
*/
pathType =
builtins.readFileType or
# Nix <2.14 compatibility shim
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(
path:
if
!pathExists path
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# Fail irrecoverably to mimic the historic behavior of this function and
# the new builtins.readFileType
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then
abort "lib.filesystem.pathType: Path ${toString path} does not exist."
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# The filesystem root is the only path where `dirOf / == /` and
# `baseNameOf /` is not valid. We can detect this and directly return
# "directory", since we know the filesystem root can't be anything else.
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else if dirOf path == path then
"directory"
else
(readDir (dirOf path)).${baseNameOf path}
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);
/*
Whether a path exists and is a directory.
Type:
pathIsDirectory :: Path -> Bool
Example:
pathIsDirectory /.
=> true
pathIsDirectory /this/does/not/exist
=> false
pathIsDirectory /some/file.nix
=> false
*/
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pathIsDirectory = path: pathExists path && pathType path == "directory";
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/*
Whether a path exists and is a regular file, meaning not a symlink or any other special file type.
Type:
pathIsRegularFile :: Path -> Bool
Example:
pathIsRegularFile /.
=> false
pathIsRegularFile /this/does/not/exist
=> false
pathIsRegularFile /some/file.nix
=> true
*/
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pathIsRegularFile = path: pathExists path && pathType path == "regular";
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/*
A map of all haskell packages defined in the given path,
identified by having a cabal file with the same name as the
directory itself.
Type: Path -> Map String Path
*/
haskellPathsInDir =
# The directory within to search
root:
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let
# Files in the root
root-files = builtins.attrNames (builtins.readDir root);
# Files with their full paths
root-files-with-paths = map (file: {
name = file;
value = root + "/${file}";
}) root-files;
# Subdirectories of the root with a cabal file.
cabal-subdirs = builtins.filter (
{ name, value }: builtins.pathExists (value + "/${name}.cabal")
) root-files-with-paths;
in
builtins.listToAttrs cabal-subdirs;
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/*
Find the first directory containing a file matching 'pattern'
upward from a given 'file'.
Returns 'null' if no directories contain a file matching 'pattern'.
Type: RegExp -> Path -> Nullable { path : Path; matches : [ MatchResults ]; }
*/
locateDominatingFile =
# The pattern to search for
pattern:
# The file to start searching upward from
file:
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let
go =
path:
let
files = builtins.attrNames (builtins.readDir path);
matches = builtins.filter (match: match != null) (map (builtins.match pattern) files);
in
if builtins.length matches != 0 then
{ inherit path matches; }
else if path == /. then
null
else
go (dirOf path);
parent = dirOf file;
isDir =
let
base = baseNameOf file;
type = (builtins.readDir parent).${base} or null;
in
file == /. || type == "directory";
in
go (if isDir then file else parent);
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/*
Given a directory, return a flattened list of all files within it recursively.
Type: Path -> [ Path ]
*/
listFilesRecursive =
# The path to recursively list
dir:
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lib.flatten (
lib.mapAttrsToList (
name: type:
if type == "directory" then
lib.filesystem.listFilesRecursive (dir + "/${name}")
else
dir + "/${name}"
) (builtins.readDir dir)
);
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/*
Transform a directory tree containing package files suitable for
`callPackage` into a matching nested attribute set of derivations.
For a directory tree like this:
```
my-packages
a.nix
b.nix
c
my-extra-feature.patch
package.nix
support-definitions.nix
my-namespace
d.nix
e.nix
f
package.nix
```
`packagesFromDirectoryRecursive` will produce an attribute set like this:
```nix
# packagesFromDirectoryRecursive {
# callPackage = pkgs.callPackage;
# directory = ./my-packages;
# }
{
a = pkgs.callPackage ./my-packages/a.nix { };
b = pkgs.callPackage ./my-packages/b.nix { };
c = pkgs.callPackage ./my-packages/c/package.nix { };
my-namespace = {
d = pkgs.callPackage ./my-packages/my-namespace/d.nix { };
e = pkgs.callPackage ./my-packages/my-namespace/e.nix { };
f = pkgs.callPackage ./my-packages/my-namespace/f/package.nix { };
};
}
```
In particular:
- If the input directory contains a `package.nix` file, then
`callPackage <directory>/package.nix { }` is returned.
- Otherwise, the input directory's contents are listed and transformed into
an attribute set.
- If a file name has the `.nix` extension, it is turned into attribute
where:
- The attribute name is the file name without the `.nix` extension
- The attribute value is `callPackage <file path> { }`
- Other files are ignored.
- Directories are turned into an attribute where:
- The attribute name is the name of the directory
- The attribute value is the result of calling
`packagesFromDirectoryRecursive { ... }` on the directory.
As a result, directories with no `.nix` files (including empty
directories) will be transformed into empty attribute sets.
Example:
packagesFromDirectoryRecursive {
inherit (pkgs) callPackage;
directory = ./my-packages;
}
=> { ... }
lib.makeScope pkgs.newScope (
self: packagesFromDirectoryRecursive {
callPackage = self.callPackage;
directory = ./my-packages;
}
)
=> { ... }
Type:
packagesFromDirectoryRecursive :: AttrSet -> AttrSet
*/
packagesFromDirectoryRecursive =
# Options.
{
/*
`pkgs.callPackage`
Type:
Path -> AttrSet -> a
*/
callPackage,
/*
The directory to read package files from
Type:
Path
*/
directory,
...
}:
let
# Determine if a directory entry from `readDir` indicates a package or
# directory of packages.
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directoryEntryIsPackage = basename: type: type == "directory" || hasSuffix ".nix" basename;
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# List directory entries that indicate packages in the given `path`.
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packageDirectoryEntries = path: filterAttrs directoryEntryIsPackage (readDir path);
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# Transform a directory entry (a `basename` and `type` pair) into a
# package.
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directoryEntryToAttrPair =
subdirectory: basename: type:
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let
path = subdirectory + "/${basename}";
in
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if type == "regular" then
{
name = removeSuffix ".nix" basename;
value = callPackage path { };
}
else if type == "directory" then
{
name = basename;
value = packagesFromDirectory path;
}
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else
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throw ''
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lib.filesystem.packagesFromDirectoryRecursive: Unsupported file type ${type} at path ${toString subdirectory}
'';
# Transform a directory into a package (if there's a `package.nix`) or
# set of packages (otherwise).
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packagesFromDirectory =
path:
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let
defaultPackagePath = path + "/package.nix";
in
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if pathExists defaultPackagePath then
callPackage defaultPackagePath { }
else
mapAttrs' (directoryEntryToAttrPair path) (packageDirectoryEntries path);
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in
packagesFromDirectory directory;
}