Merge pull request #267294 from fricklerhandwerk/note-trivial-builders

rec {

  /* Run the shell command `buildCommand' to produce a store path named

   `name'.  The attributes in `env' are added to the environment

   prior to running the command. By default `runCommand` runs in a

   stdenv with no compiler environment. `runCommandCC` uses the default

   stdenv, `pkgs.stdenv`.

  /*

    Run the shell command `buildCommand' to produce a store path named `name'.

    The attributes in `env' are added to the environment prior to running the command.

    Environment variables set by `stdenv.mkDerivation` take precedence.

    By default `runCommand` runs in a stdenv with no compiler environment.

    `runCommandCC` uses the default stdenv, `pkgs.stdenv`.

    Example:

    ```nix

    runCommand "name" {envVariable = true;} ''echo hello > $out'';

    ```

   runCommand "name" {envVariable = true;} ''echo hello > $out''

    ```nix

    runCommandCC "name" {} ''gcc -o myfile myfile.c; cp myfile $out'';

    ```

    The `*Local` variants force a derivation to be built locally,

    it is not substituted.

    It is the same as adding the special fields

   `preferLocalBuild = true;`

   `allowSubstitutes = false;`

    ```nix

    {

      preferLocalBuild = true;

      allowSubstitutes = false;

    }

    ```

    to a derivation’s attributes.

  */

  # `runCommandCCLocal` left out on purpose.

  # We shouldn’t force the user to have a cc in scope.

  /* Generalized version of the `runCommand`-variants

  /*

    Generalized version of the `runCommand`-variants

    which does customized behavior via a single

    attribute set passed as the first argument

    instead of having a lot of variants like

      // builtins.removeAttrs derivationArgs [ "passAsFile" ]);

  /* Writes a text file to the nix store.

  /*

    Writes a text file to the nix store.

    The contents of text is added to the file in the store.

    Example:

      matches = builtins.match "/bin/([^/]+)" destination;

    in

    runCommand name

      { inherit text executable checkPhase allowSubstitutes preferLocalBuild;

      {

        inherit text executable checkPhase allowSubstitutes preferLocalBuild;

        passAsFile = [ "text" ];

        meta = lib.optionalAttrs (executable && matches != null) {

        meta = lib.optionalAttrs (executable && matches != null)

          {

            mainProgram = lib.head matches;

          } // meta;

      }

        inherit preferLocalBuild allowSubstitutes;

        passAsFile = [ "paths" ];

      }; # pass the defaults

    in runCommand name args

    in

    runCommand name args

      ''

        mkdir -p $out

        for i in $(cat $pathsPath); do

        else if (lib.isList entries) then lib.foldl (a: b: a // { "${b.name}" = b.path; }) { } entries

        else throw "linkFarm entries must be either attrs or a list!";

    linkCommands = lib.mapAttrsToList (name: path: ''

      linkCommands = lib.mapAttrsToList

        (name: path: ''

          mkdir -p "$(dirname ${lib.escapeShellArg "${name}"})"

          ln -s ${lib.escapeShellArg "${path}"} ${lib.escapeShellArg "${name}"}

    '') entries';

        '')

        entries';

    in

  runCommand name {

    runCommand name

      {

        preferLocalBuild = true;

        allowSubstitutes = false;

        passthru.entries = entries';

    }

   */

  requireFile = { name ? null

  requireFile =

    { name ? null

    , sha256 ? null

    , sha1 ? null

    , hash ? null

      assert (message != null) || (url != null);

      assert (sha256 != null) || (sha1 != null) || (hash != null);

      assert (name != null) || (url != null);

    let msg =

      let

        msg =

          if message != null then message

          else ''

            Unfortunately, we cannot download file ${name_} automatically.

            or

              nix-prefetch-url --type ${hashAlgo} file:///path/to/${name_}

          '';

      hashAlgo = if hash != null then (builtins.head (lib.strings.splitString "-" hash))

        hashAlgo =

          if hash != null then (builtins.head (lib.strings.splitString "-" hash))

          else if sha256 != null then "sha256"

          else "sha1";

        hashAlgo_ = if hash != null then "" else hashAlgo;

      hash_ = if hash != null then hash

        hash_ =

          if hash != null then hash

          else if sha256 != null then sha256

          else sha1;

        name_ = if name == null then baseNameOf (toString url) else name;

    , patches ? [ ]

    , postPatch ? ""

    , ...

    }@args: stdenvNoCC.mkDerivation {

    }@args: stdenvNoCC.mkDerivation

      {

        inherit name src patches postPatch;

        preferLocalBuild = true;

        allowSubstitutes = false;

    // (removeAttrs args [ "src" "name" "patches" "postPatch" ]);

  /* An immutable file in the store with a length of 0 bytes. */

  emptyFile = runCommand "empty-file" {

  emptyFile = runCommand "empty-file"

    {

      outputHashAlgo = "sha256";

      outputHashMode = "recursive";

      outputHash = "0ip26j2h11n1kgkz36rl4akv694yz65hr72q4kv4b3lxcbi65b3p";

    } "touch $out";

  /* An immutable empty directory in the store. */

  emptyDirectory = runCommand "empty-directory" {

  emptyDirectory = runCommand "empty-directory"

    {

      outputHashAlgo = "sha256";

      outputHashMode = "recursive";

      outputHash = "0sjjj9z1dhilhpc8pq4154czrb79z9cm044jvn75kxcjv6v5l2m5";