build(nix): add a way to override what grammars get built (#3141)

flake.nix

@@ -18,7 +18,8 @@
     nixpkgs,
     nixCargoIntegration,
     ...
-  }:
+  }: let
+    outputs = config:
       nixCargoIntegration.lib.makeOutputs {
         root = ./.;
         renameOutputs = {"helix-term" = "helix";};
@@ -42,14 +43,14 @@
                   path = "${common.root}/${rel}";
                   name = rel;
                 };
-            grammars = pkgs.callPackage ./grammars.nix {};
+              grammars = pkgs.callPackage ./grammars.nix config;
               runtimeDir = pkgs.runCommandNoCC "helix-runtime" {} ''
                 mkdir -p $out
                 ln -s ${mkRootPath "runtime"}/* $out
                 rm -r $out/grammars
                 ln -s ${grammars} $out/grammars
               '';
-          in {
+              overridedAttrs = {
                 # disable fetching and building of tree-sitter grammars in the helix-term build.rs
                 HELIX_DISABLE_AUTO_GRAMMAR_BUILD = "1";
                 # link languages and theme toml files since helix-term expects them (for tests)
@@ -67,6 +68,13 @@
                   fi
                 '';
               };
+            in
+              overridedAttrs
+              // (
+                pkgs.lib.optionalAttrs
+                (config ? makeWrapperArgs)
+                {inherit (config) makeWrapperArgs;}
+              );
           };
           shell = common: prev: {
             packages =
@@ -96,6 +104,30 @@
           };
         };
       };
+    defaultOutputs = outputs {};
+    makeOverridableHelix = system: old:
+      old
+      // {
+        override = args:
+          makeOverridableHelix
+          system
+          (outputs args).packages.${system}.helix;
+      };
+  in
+    defaultOutputs
+    // {
+      packages =
+        nixpkgs.lib.mapAttrs
+        (
+          system: packages:
+            packages
+            // rec {
+              default = helix;
+              helix = makeOverridableHelix system packages.helix;
+            }
+        )
+        defaultOutputs.packages;
+    };
 
   nixConfig = {
     extra-substituters = ["https://helix.cachix.org"];

grammars.nix

@@ -4,6 +4,8 @@
   runCommandLocal,
   runCommandNoCC,
   yj,
+  includeGrammarIf ? _: true,
+  ...
 }: let
   # HACK: nix < 2.6 has a bug in the toml parser, so we convert to JSON
   # before parsing
@@ -102,12 +104,13 @@
         runHook postFixup
       '';
     };
+  grammarsToBuild = builtins.filter includeGrammarIf gitGrammars;
   builtGrammars =
     builtins.map (grammar: {
       inherit (grammar) name;
       artifact = buildGrammar grammar;
     })
-    gitGrammars;
+    grammarsToBuild;
   grammarLinks =
     builtins.map (grammar: "ln -s ${grammar.artifact}/${grammar.name}.so $out/${grammar.name}.so")
     builtGrammars;