replaceVars: init

{ lib, stdenvNoCC }:

/**

  `replaceVars` is a wrapper around the [bash function `substitute`](https://nixos.org/manual/nixpkgs/stable/#fun-substitute)

  in the stdenv. It allows for terse replacement of names in the specified path, while checking

  for common mistakes such as naming a replacement that does nothing or forgetting a variable which

  needs to be replaced.

  As with the [`--subst-var-by`](https://nixos.org/manual/nixpkgs/stable/#fun-substitute-subst-var-by)

  flag, names are encoded as `@name@` in the provided file at the provided path.

  Any unmatched variable names in the file at the provided path will cause a build failure.

  Any remaining text that matches `@[A-Za-z_][0-9A-Za-z_'-]@` in the output after replacement

  has occurred will cause a build failure.

  # Inputs

  `path` ([Store Path](https://nixos.org/manual/nix/latest/store/store-path.html#store-path) String)

  : The file in which to replace variables.

  `attrs` (AttrsOf String)

  : Each entry in this set corresponds to a `--subst-var-by` entry in [`substitute`](https://nixos.org/manual/nixpkgs/stable/#fun-substitute).

  # Example

  ```nix

  { replaceVars }:

  replaceVars ./greeting.txt { world = "hello"; }

  ```

  See `../../test/replace-vars/default.nix` for tests of this function.

*/

path: attrs:

let

  # We use `--replace-fail` instead of `--subst-var-by` so that if the thing isn't there, we fail.

  subst-var-by = name: value: [

    "--replace-fail"

    (lib.escapeShellArg "@${name}@")

    (lib.escapeShellArg value)

  ];

  replacements = lib.concatLists (lib.mapAttrsToList subst-var-by attrs);

in

stdenvNoCC.mkDerivation {

  name = baseNameOf (toString path);

  src = path;

  doCheck = true;

  dontUnpack = true;

  preferLocalBuild = true;

  allowSubstitutes = false;

  buildPhase = ''

    runHook preBuild

    substitute "$src" "$out" ${lib.concatStringsSep " " replacements}

    runHook postBuild

  '';

  # Look for Nix identifiers surrounded by `@` that aren't substituted.

  checkPhase =

    let

      regex = lib.escapeShellArg "@[a-zA-Z_][0-9A-Za-z_'-]*@";

    in

    ''

      runHook preCheck

      if grep -qe ${regex} "$out"; then

        echo The following look like unsubstituted Nix identifiers that remain in "$out":

        grep -oe ${regex} "$out"

        echo Use the more precise '`substitute`' function if this check is in error.

        exit 1

      fi

      runHook postCheck

    '';

}

  systemd = callPackage ./systemd { };

  replaceVars = recurseIntoAttrs (callPackage ./replace-vars { });

  substitute = recurseIntoAttrs (callPackage ./substitute { });

}

{

  replaceVars,

  emptyDirectory,

  emptyFile,

  runCommand,

  testers,

}:

let

  inherit (testers) testEqualContents testBuildFailure;

in

{

  # Success case for `replaceVars`.

  replaceVars = testEqualContents {

    assertion = "replaceVars";

    actual = replaceVars ./source.txt {

      free = "free";

      "equal in" = "are the same in";

      brotherhood = "shared humanity";

    };

    expected = builtins.toFile "expected" ''

      All human beings are born free and are the same in dignity and rights.

      They are endowed with reason and conscience and should act towards

      one another in a spirit of shared humanity.

        -- eroosevelt@humanrights.un.org

    '';

  };

  # There might eventually be a usecase for this, but it's not supported at the moment.

  replaceVars-fails-on-directory =

    runCommand "replaceVars-fails" { failed = testBuildFailure (replaceVars emptyDirectory { }); }

      ''

        grep -e "ERROR: file.*empty-directory.*does not exist" $failed/testBuildFailure.log

        touch $out

      '';

  replaceVars-fails-in-build-phase =

    runCommand "replaceVars-fails"

      { failed = testBuildFailure (replaceVars emptyFile { not-found = "boo~"; }); }

      ''

        grep -e "ERROR: pattern @not-found@ doesn't match anything in file.*empty-file" $failed/testBuildFailure.log

        touch $out

      '';

  replaceVars-fails-in-check-phase =

    runCommand "replaceVars-fails"

      {

        failed =

          let

            src = builtins.toFile "source.txt" ''

              Header.

              before @whatIsThis@ middle @It'sOdd2Me@ after.

              @cannot detect due to space@

              Trailer.

            '';

          in

          testBuildFailure (replaceVars src { });

      }

      ''

        grep -e "unsubstituted Nix identifiers.*source.txt" $failed/testBuildFailure.log

        grep -F "@whatIsThis@" $failed/testBuildFailure.log

        grep -F "@It'sOdd2Me@" $failed/testBuildFailure.log

        grep -F 'more precise `substitute` function' $failed/testBuildFailure.log

        # Shouldn't see irrelevant details.

        ! grep -q -E -e "Header|before|middle|after|Trailer" $failed/testBuildFailure.log

        # Shouldn't see the "cannot detect" version.

        ! grep -q -F "cannot detect due to space" $failed/testBuildFailure.log

        touch $out

      '';

}

All human beings are born @free@ and @equal in@ dignity and rights.

They are endowed with reason and conscience and should act towards

one another in a spirit of @brotherhood@.

  -- eroosevelt@humanrights.un.org

  replaceDependency = callPackage ../build-support/replace-dependency.nix { };

  replaceVars = callPackage ../build-support/replace-vars { };

  nukeReferences = callPackage ../build-support/nuke-references {

    inherit (darwin) signingUtils;

  };