genemichaels: init

Adds a module to use the genemichaels formatter for Rust files that is
compatible with version 0.5.7.

examples/formatter-genemichaels.toml

@@ -0,0 +1,6 @@
+# Example generated by ../examples.sh
+[formatter.genemichaels]
+command = "genemichaels"
+excludes = []
+includes = ["*.rs"]
+options = ["--config", "/nix/store/vx37ijcbwxg86nws25wrhaz96mrs4ady-genemichaels.json"]

programs/genemichaels.nix

@@ -0,0 +1,165 @@
+{ lib
+, pkgs
+, config
+, ...
+}:
+let
+  cfg = config.programs.genemichaels;
+  configFormat = pkgs.formats.json { };
+
+  inherit (lib)
+    types
+    ;
+
+  inherit (lib.lists)
+    optionals
+    ;
+
+  inherit (lib.modules)
+    mkIf
+    ;
+
+  inherit (lib.options)
+    mkEnableOption
+    mkOption
+    mkPackageOption
+    ;
+in
+{
+  meta.maintainers = [ "djacu" ];
+
+  options.programs.genemichaels = {
+    enable = mkEnableOption "genemichaels";
+    package = mkPackageOption pkgs "genemichaels" { };
+
+    # Configuration scheme for genemichaels, which we generate .genemichaels.json with.
+    # Definition taken from https://github.com/andrewbaxter/genemichaels/blob/genemichaels-v0.5.7/readme.md#configuration
+    settings = {
+      max_width = mkOption {
+        description = ''
+          Ideal maximum line width. If there's an unbreakable element the line
+          won't be split.
+        '';
+        type = types.ints.positive;
+        example = 80;
+        default = 120;
+      };
+      root_splits = mkOption {
+        description = ''
+          When breaking a child element, also break all parent elements.
+        '';
+        type = types.bool;
+        example = true;
+        default = false;
+      };
+      split_brace_threshold = mkOption {
+        description = ''
+          Break a `()` or `{}` if it has greater than this number of children.
+          Set to `null` to disable breaking due to high child counts.
+        '';
+        type = types.nullOr types.ints.positive;
+        example = null;
+        default = 1;
+      };
+      split_attributes = mkOption {
+        description = ''
+          Break a `#[]` on a separate line before the element it's associated
+          with.
+        '';
+        type = types.bool;
+        example = false;
+        default = true;
+      };
+      split_where = mkOption {
+        description = ''
+          Put the `where` clause on a new line.
+        '';
+        type = types.bool;
+        example = false;
+        default = true;
+      };
+      comment_width = mkOption {
+        description = ''
+          Maximum relative line length for comments (past the comment
+          indentation level). Can be `null` to disable relative wrapping. If
+          disabled, still wraps at `max_width`.
+        '';
+        type = types.nullOr types.ints.positive;
+        example = null;
+        default = 80;
+      };
+      comment_errors_fatal = mkOption {
+        description = ''
+          If reformatting comments results in an error, abort formatting the
+          document.
+        '';
+        type = types.bool;
+        example = true;
+        default = false;
+      };
+      keep_max_blank_lines = mkOption {
+        description = ''
+          Genemichaels will replace line breaks with it's own deterministic
+          line breaks. You can use this to keep extra line breaks (1 will keep
+          up to 1 extra line break) during comment extraction. This is unused
+          during formatting.
+        '';
+        type = types.ints.unsigned;
+        example = 1;
+        default = 0;
+      };
+    };
+
+    settingsFile = mkOption {
+      description = "The configuration file used by `genemichaels`.";
+      type = types.path;
+      example = ./.genemichaels.json;
+      default = configFormat.generate ".genemichaels.json" cfg.settings;
+    };
+
+    threadCount = mkOption {
+      description = ''
+        How many threads to use for formatting multiple files. Set to `null` to
+        default to the number of cores on the system.
+      '';
+      type = types.nullOr types.ints.unsigned;
+      example = 1;
+      default = null;
+    };
+
+    includes = mkOption {
+      description = ''
+        Path / file patterns to include for genemichaels.
+      '';
+      type = types.listOf types.str;
+      default = [
+        "*.rs"
+      ];
+    };
+
+    excludes = mkOption {
+      description = ''
+        Path / file patterns to exclude for genemichaels.
+      '';
+      type = types.listOf types.str;
+      default = [ ];
+    };
+  };
+
+  config = mkIf cfg.enable {
+    settings.formatter.genemichaels = {
+      command = "${cfg.package}/bin/genemichaels";
+      options =
+        (optionals (cfg.threadCount != null) [
+          "--thread-count"
+          (toString cfg.threadCount)
+        ])
+        ++ [
+          "--config"
+          (toString cfg.settingsFile)
+        ];
+      includes = cfg.includes;
+      excludes = cfg.excludes;
+    };
+  };
+}