doc: migrate filesets to doc-comment format (#303811)

/*

/**

  <!-- This anchor is here for backwards compatibility -->

  []{#sec-fileset}

  A file set is a (mathematical) set of local files that can be added to the Nix store for use in Nix derivations.

  File sets are easy and safe to use, providing obvious and composable semantics with good error messages to prevent mistakes.

  ## Overview {#sec-fileset-overview}

  # Overview {#sec-fileset-overview}

  Basics:

  - [Implicit coercion from paths to file sets](#sec-fileset-path-coercion)

  see [this issue](https://github.com/NixOS/nixpkgs/issues/266356) to request it.

  ## Implicit coercion from paths to file sets {#sec-fileset-path-coercion}

  # Implicit coercion from paths to file sets {#sec-fileset-path-coercion}

  All functions accepting file sets as arguments can also accept [paths](https://nixos.org/manual/nix/stable/language/values.html#type-path) as arguments.

  Such path arguments are implicitly coerced to file sets containing all files under that path:

  This is in contrast to using [paths in string interpolation](https://nixos.org/manual/nix/stable/language/values.html#type-path), which does add the entire referenced path to the store.

  :::

  ### Example {#sec-fileset-path-coercion-example}

  ## Example {#sec-fileset-path-coercion-example}

  Assume we are in a local directory with a file hierarchy like this:

  ```

in {

  /*

  /**

    Create a file set from a path that may or may not exist:

    - If the path does exist, the path is [coerced to a file set](#sec-fileset-path-coercion).

    - If the path does not exist, a file set containing no files is returned.

    Type:

    # Inputs

    `path`

    : 1\. Function argument

    # Type

    ```

    maybeMissing :: Path -> FileSet

    ```

    # Examples

    :::{.example}

    ## `lib.fileset.maybeMissing` usage example

    Example:

    ```nix

    # All files in the current directory, but excluding main.o if it exists

    difference ./. (maybeMissing ./main.o)

    ```

    :::

  */

  maybeMissing =

    path:

    else

      _singleton path;

  /*

  /**

    Incrementally evaluate and trace a file set in a pretty way.

    This function is only intended for debugging purposes.

    The exact tracing format is unspecified and may change.

    This variant is useful for tracing file sets in the Nix repl.

    Type:

    # Inputs

    `fileset`

    : The file set to trace.

      This argument can also be a path,

      which gets [implicitly coerced to a file set](#sec-fileset-path-coercion).

    `val`

    : The value to return.

    # Type

    ```

    trace :: FileSet -> Any -> Any

    ```

    Example:

    # Examples

    :::{.example}

    ## `lib.fileset.trace` usage example

    ```nix

    trace (unions [ ./Makefile ./src ./tests/run.sh ]) null

    =>

    trace: /home/user/src/myProject

    trace: - tests

    trace:   - run.sh (regular)

    null

  */

  trace =

    /*

    The file set to trace.

    ```

    This argument can also be a path,

    which gets [implicitly coerced to a file set](#sec-fileset-path-coercion).

    :::

  */

    fileset:

  trace = fileset:

    let

      # "fileset" would be a better name, but that would clash with the argument name,

      # and we cannot change that because of https://github.com/nix-community/nixdoc/issues/76

      (_printFileset actualFileset)

      (x: x);

  /*

  /**

    Incrementally evaluate and trace a file set in a pretty way.

    This function is only intended for debugging purposes.

    The exact tracing format is unspecified and may change.

    This variant is useful for tracing file sets passed as arguments to other functions.

    Type:

    # Inputs

    `fileset`

    : The file set to trace and return.

      This argument can also be a path,

      which gets [implicitly coerced to a file set](#sec-fileset-path-coercion).

    # Type

    ```

    traceVal :: FileSet -> FileSet

    ```

    # Examples

    :::{.example}

    ## `lib.fileset.traceVal` usage example

    Example:

    ```nix

    toSource {

      root = ./.;

      fileset = traceVal (unions [

    trace: - tests

    trace:   - run.sh (regular)

    "/nix/store/...-source"

  */

  traceVal =

    /*

    The file set to trace and return.

    ```

    This argument can also be a path,

    which gets [implicitly coerced to a file set](#sec-fileset-path-coercion).

    :::

  */

    fileset:

  traceVal = fileset:

    let

      # "fileset" would be a better name, but that would clash with the argument name,

      # and we cannot change that because of https://github.com/nix-community/nixdoc/issues/76

      # but that would then duplicate work for consumers of the fileset, because then they have to coerce it again

      actualFileset;

  /*

  /**

    Add the local files contained in `fileset` to the store as a single [store path](https://nixos.org/manual/nix/stable/glossary#gloss-store-path) rooted at `root`.

    The result is the store path as a string-like value, making it usable e.g. as the `src` of a derivation, or in string interpolation:

    The name of the store path is always `source`.

    Type:

    # Inputs

    Takes an attribute set with the following attributes

    `root` (Path; _required_)

    : The local directory [path](https://nixos.org/manual/nix/stable/language/values.html#type-path) that will correspond to the root of the resulting store path.

      Paths in [strings](https://nixos.org/manual/nix/stable/language/values.html#type-string), including Nix store paths, cannot be passed as `root`.

      `root` has to be a directory.

      :::{.note}

      Changing `root` only affects the directory structure of the resulting store path, it does not change which files are added to the store.

      The only way to change which files get added to the store is by changing the `fileset` attribute.

      :::

    `fileset` (FileSet; _required_)

    : The file set whose files to import into the store.

      File sets can be created using other functions in this library.

      This argument can also be a path,

      which gets [implicitly coerced to a file set](#sec-fileset-path-coercion).

      :::{.note}

      If a directory does not recursively contain any file, it is omitted from the store path contents.

      :::

    # Type

    ```

    toSource :: {

      root :: Path,

      fileset :: FileSet,

    } -> SourceLike

    ```

    Example:

    # Examples

    :::{.example}

    ## `lib.fileset.toSource` usage example

    ```nix

    # Import the current directory into the store

    # but only include files under ./src

    toSource {

      fileset = ./.;

    }

    => <error>

  */

  toSource = {

    /*

      (required) The local directory [path](https://nixos.org/manual/nix/stable/language/values.html#type-path) that will correspond to the root of the resulting store path.

      Paths in [strings](https://nixos.org/manual/nix/stable/language/values.html#type-string), including Nix store paths, cannot be passed as `root`.

      `root` has to be a directory.

    ```

      :::{.note}

      Changing `root` only affects the directory structure of the resulting store path, it does not change which files are added to the store.

      The only way to change which files get added to the store is by changing the `fileset` attribute.

    :::

  */

  toSource = {

    root,

    /*

      (required) The file set whose files to import into the store.

      File sets can be created using other functions in this library.

      This argument can also be a path,

      which gets [implicitly coerced to a file set](#sec-fileset-path-coercion).

      :::{.note}

      If a directory does not recursively contain any file, it is omitted from the store path contents.

      :::

    */

    fileset,

  }:

    let

      };

  /*

  /**

    The list of file paths contained in the given file set.

    :::{.note}

    The resulting list of files can be turned back into a file set using [`lib.fileset.unions`](#function-library-lib.fileset.unions).

    Type:

    # Inputs

    `fileset`

    : The file set whose file paths to return. This argument can also be a path, which gets [implicitly coerced to a file set](#sec-fileset-path-coercion).

    # Type

    ```

    toList :: FileSet -> [ Path ]

    ```

    Example:

    # Examples

    :::{.example}

    ## `lib.fileset.toList` usage example

    ```nix

    toList ./.

    [ ./README.md ./Makefile ./src/main.c ./src/main.h ]

    toList (difference ./. ./src)

    [ ./README.md ./Makefile ]

    ```

    :::

  */

  toList =

    # The file set whose file paths to return.

    # This argument can also be a path,

    # which gets [implicitly coerced to a file set](#sec-fileset-path-coercion).

    fileset:

  toList = fileset:

    _toList (_coerce "lib.fileset.toList: Argument" fileset);

  /*

  /**

    The file set containing all files that are in either of two given file sets.

    This is the same as [`unions`](#function-library-lib.fileset.unions),

    but takes just two file sets instead of a list.

    The given file sets are evaluated as lazily as possible,

    with the first argument being evaluated first if needed.

    Type:

    # Inputs

    `fileset1`

    : The first file set. This argument can also be a path, which gets [implicitly coerced to a file set](#sec-fileset-path-coercion).

    `fileset2`

    : The second file set. This argument can also be a path, which gets [implicitly coerced to a file set](#sec-fileset-path-coercion).

    # Type

    ```

    union :: FileSet -> FileSet -> FileSet

    ```

    Example:

    # Examples

    :::{.example}

    ## `lib.fileset.union` usage example

    ```nix

    # Create a file set containing the file `Makefile`

    # and all files recursively in the `src` directory

    union ./Makefile ./src

    # Create a file set containing the file `Makefile`

    # and the LICENSE file from the parent directory

    union ./Makefile ../LICENSE

    ```

    :::

  */

  union =

    # The first file set.

    # This argument can also be a path,

    # which gets [implicitly coerced to a file set](#sec-fileset-path-coercion).

    fileset1:

    # The second file set.

    # This argument can also be a path,

    # which gets [implicitly coerced to a file set](#sec-fileset-path-coercion).

    fileset2:

    _unionMany

      (_coerceMany "lib.fileset.union" [

        }

      ]);

  /*

  /**

    The file set containing all files that are in any of the given file sets.

    This is the same as [`union`](#function-library-lib.fileset.unions),

    but takes a list of file sets instead of just two.

    The given file sets are evaluated as lazily as possible,

    with earlier elements being evaluated first if needed.

    Type:

    # Inputs

    `filesets`

    : A list of file sets. The elements can also be paths, which get [implicitly coerced to file sets](#sec-fileset-path-coercion).

    # Type

    ```

    unions :: [ FileSet ] -> FileSet

    ```

    # Examples

    :::{.example}

    ## `lib.fileset.unions` usage example

    Example:

    ```nix

    # Create a file set containing selected files

    unions [

      # Include the single file `Makefile` in the current directory

      # Include the `LICENSE` file from the parent directory

      ../LICENSE

    ]

    ```

    :::

  */

  unions =

    # A list of file sets.

    # The elements can also be paths,

    # which get [implicitly coerced to file sets](#sec-fileset-path-coercion).

    filesets:

    if ! isList filesets then

      throw ''

        _unionMany

      ];

  /*

  /**

    The file set containing all files that are in both of two given file sets.

    See also [Intersection (set theory)](https://en.wikipedia.org/wiki/Intersection_(set_theory)).

    The given file sets are evaluated as lazily as possible,

    with the first argument being evaluated first if needed.

    Type:

    # Inputs

    `fileset1`

    : The first file set. This argument can also be a path, which gets [implicitly coerced to a file set](#sec-fileset-path-coercion).

    `fileset2`

    : The second file set. This argument can also be a path, which gets [implicitly coerced to a file set](#sec-fileset-path-coercion).

    # Type

    ```

    intersection :: FileSet -> FileSet -> FileSet

    ```

    # Examples

    :::{.example}

    ## `lib.fileset.intersection` usage example

    Example:

    ```nix

    # Limit the selected files to the ones in ./., so only ./src and ./Makefile

    intersection ./. (unions [ ../LICENSE ./src ./Makefile ])

    ```

    :::

  */

  intersection =

    # The first file set.

    # This argument can also be a path,

    # which gets [implicitly coerced to a file set](#sec-fileset-path-coercion).

    fileset1:

    # The second file set.

    # This argument can also be a path,

    # which gets [implicitly coerced to a file set](#sec-fileset-path-coercion).

    fileset2:

    let

      filesets = _coerceMany "lib.fileset.intersection" [

      (elemAt filesets 0)

      (elemAt filesets 1);

  /*

  /**

    The file set containing all files from the first file set that are not in the second file set.

    See also [Difference (set theory)](https://en.wikipedia.org/wiki/Complement_(set_theory)#Relative_complement).

    The given file sets are evaluated as lazily as possible,

    with the first argument being evaluated first if needed.

    Type:

    # Inputs

    `positive`

    : The positive file set. The result can only contain files that are also in this file set.  This argument can also be a path, which gets [implicitly coerced to a file set](#sec-fileset-path-coercion).

    `negative`

    : The negative file set. The result will never contain files that are also in this file set.  This argument can also be a path, which gets [implicitly coerced to a file set](#sec-fileset-path-coercion).

    # Type

    ```

    union :: FileSet -> FileSet -> FileSet

    ```

    # Examples

    :::{.example}

    ## `lib.fileset.difference` usage example

    Example:

    ```nix

    # Create a file set containing all files from the current directory,

    # except ones under ./tests

    difference ./. ./tests

    # Create a file set containing all files under ./tests, except ones in `nixFiles`,

    # meaning only without ./tests/default.nix

    difference ./tests nixFiles

    ```

    :::

  */

  difference =

    # The positive file set.

    # The result can only contain files that are also in this file set.

    #

    # This argument can also be a path,

    # which gets [implicitly coerced to a file set](#sec-fileset-path-coercion).

    positive:

    # The negative file set.

    # The result will never contain files that are also in this file set.

    #

    # This argument can also be a path,

    # which gets [implicitly coerced to a file set](#sec-fileset-path-coercion).

    negative:

    let

      filesets = _coerceMany "lib.fileset.difference" [

      (elemAt filesets 0)

      (elemAt filesets 1);

  /*

  /**

    Filter a file set to only contain files matching some predicate.

    Type:

    # Inputs

    `predicate`

    : The predicate function to call on all files contained in given file set.

      A file is included in the resulting file set if this function returns true for it.

      This function is called with an attribute set containing these attributes:

      - `name` (String): The name of the file

      - `type` (String, one of `"regular"`, `"symlink"` or `"unknown"`): The type of the file.

        This matches result of calling [`builtins.readFileType`](https://nixos.org/manual/nix/stable/language/builtins.html#builtins-readFileType) on the file's path.

      - `hasExt` (String -> Bool): Whether the file has a certain file extension.

        `hasExt ext` is true only if `hasSuffix ".${ext}" name`.

        This also means that e.g. for a file with name `.gitignore`,

        `hasExt "gitignore"` is true.

      Other attributes may be added in the future.

    `path`

    : The path whose files to filter

    # Type

    ```

    fileFilter ::

      ({

        name :: String,

      } -> Bool)

      -> Path

      -> FileSet

    ```

    # Examples

    :::{.example}

    ## `lib.fileset.fileFilter` usage example

    Example:

    ```nix

    # Include all regular `default.nix` files in the current directory

    fileFilter (file: file.name == "default.nix") ./.

    # Include all regular files (not symlinks or others) in the current directory

    fileFilter (file: file.type == "regular") ./.

  */

  fileFilter =

    /*

      The predicate function to call on all files contained in given file set.

      A file is included in the resulting file set if this function returns true for it.

      This function is called with an attribute set containing these attributes:

      - `name` (String): The name of the file

      - `type` (String, one of `"regular"`, `"symlink"` or `"unknown"`): The type of the file.

        This matches result of calling [`builtins.readFileType`](https://nixos.org/manual/nix/stable/language/builtins.html#builtins-readFileType) on the file's path.

      - `hasExt` (String -> Bool): Whether the file has a certain file extension.

        `hasExt ext` is true only if `hasSuffix ".${ext}" name`.

        This also means that e.g. for a file with name `.gitignore`,

        `hasExt "gitignore"` is true.

    ```

      Other attributes may be added in the future.

    :::

  */

  fileFilter =

    predicate:

    # The path whose files to filter

    path:

    if ! isFunction predicate then

      throw ''

    else

      _fileFilter predicate path;

  /*

  /**

    Create a file set with the same files as a `lib.sources`-based value.

    This does not import any of the files into the store.

    Turning the result of this function back into a source using `toSource` will therefore not preserve empty directories.

    :::

  Type:

    # Inputs

    `source`

    : 1\. Function argument

    # Type

    ```

    fromSource :: SourceLike -> FileSet

    ```

    # Examples

    :::{.example}

    ## `lib.fileset.fromSource` usage example

  Example:

    ```nix

    # There's no cleanSource-like function for file sets yet,

    # but we can just convert cleanSource to a file set and use it that way

    toSource {

        ./Makefile

        ./src

      ]);

    ```

    :::

  */

  fromSource = source:

    let

      # If there's no filter, no need to run the expensive conversion, all subpaths will be included

      _singleton path;

  /*

  /**

    Create a file set containing all [Git-tracked files](https://git-scm.com/book/en/v2/Git-Basics-Recording-Changes-to-the-Repository) in a repository.

    This function behaves like [`gitTrackedWith { }`](#function-library-lib.fileset.gitTrackedWith) - using the defaults.

    Type:

    # Inputs

    `path`

    : The [path](https://nixos.org/manual/nix/stable/language/values#type-path) to the working directory of a local Git repository.

      This directory must contain a `.git` file or subdirectory.

    # Type

    ```

    gitTracked :: Path -> FileSet

    ```

    # Examples

    :::{.example}

    ## `lib.fileset.gitTracked` usage example

    Example:

    ```nix

    # Include all files tracked by the Git repository in the current directory

    gitTracked ./.

    # Include only files tracked by the Git repository in the parent directory

    # that are also in the current directory

    intersection ./. (gitTracked ../.)

    ```

    :::

  */

  gitTracked =

    /*

      The [path](https://nixos.org/manual/nix/stable/language/values#type-path) to the working directory of a local Git repository.

      This directory must contain a `.git` file or subdirectory.

    */

    path:

    _fromFetchGit

      "gitTracked"

      path

      {};

  /*

  /**

    Create a file set containing all [Git-tracked files](https://git-scm.com/book/en/v2/Git-Basics-Recording-Changes-to-the-Repository) in a repository.

    The first argument allows configuration with an attribute set,

    while the second argument is the path to the Git working tree.

    This may change in the future.

    :::

    Type:

    # Inputs

    `options` (attribute set)

    : `recurseSubmodules` (optional, default: `false`)

      : Whether to recurse into [Git submodules](https://git-scm.com/book/en/v2/Git-Tools-Submodules) to also include their tracked files.

        If `true`, this is equivalent to passing the [--recurse-submodules](https://git-scm.com/docs/git-ls-files#Documentation/git-ls-files.txt---recurse-submodules) flag to `git ls-files`.

      `path`

      : The [path](https://nixos.org/manual/nix/stable/language/values#type-path) to the working directory of a local Git repository.

        This directory must contain a `.git` file or subdirectory.

    # Type

    ```

    gitTrackedWith :: { recurseSubmodules :: Bool ? false } -> Path -> FileSet

    ```

    # Examples

    :::{.example}

    ## `lib.fileset.gitTrackedWith` usage example

    Example:

    ```nix

    # Include all files tracked by the Git repository in the current directory

    # and any submodules under it

    gitTracked { recurseSubmodules = true; } ./.

    ```

    :::

  */

  gitTrackedWith =

    {

      /*

        (optional, default: `false`) Whether to recurse into [Git submodules](https://git-scm.com/book/en/v2/Git-Tools-Submodules) to also include their tracked files.

        If `true`, this is equivalent to passing the [--recurse-submodules](https://git-scm.com/docs/git-ls-files#Documentation/git-ls-files.txt---recurse-submodules) flag to `git ls-files`.

      */

      recurseSubmodules ? false,

    }:

    /*

      The [path](https://nixos.org/manual/nix/stable/language/values#type-path) to the working directory of a local Git repository.

      This directory must contain a `.git` file or subdirectory.

    */

    path:

    if ! isBool recurseSubmodules then

      throw "lib.fileset.gitTrackedWith: Expected the attribute `recurseSubmodules` of the first argument to be a boolean, but it's a ${typeOf recurseSubmodules} instead."