lsp: experimental vendoring stuff

modules/neovim/init/lsp.nix

@@ -6,7 +6,7 @@
   inherit (builtins) filter;
   inherit (lib.modules) mkIf mkMerge mkDefault;
   inherit (lib.options) mkOption mkEnableOption;
-  inherit (lib.types) attrsOf;
+  inherit (lib.types) attrsOf enum;
   inherit (lib.strings) concatLines;
   inherit (lib.attrsets) mapAttrsToList attrNames filterAttrs;
   inherit (lib.generators) mkLuaInline;
@@ -70,6 +70,29 @@ in {
           on the underlying API.
         '';
       };
+
+      vendorPrograms = mkOption {
+        type = enum ["path" "exact" "never"];
+        default = "exact";
+        description = ''
+          How NVF should install LSP packages.
+
+          - "path": Append program paths to PATH, this means other programs on
+            your system or devshell will take precedence, so the vendored
+            package only acts as a fallback when you have none installed.
+          - "exact": Commands are passed as full path to the program in the nix
+            store. Programs on your PATH are never used.
+          - "never": Never vendor LSP packages. Language servers are searched
+            for in PATH
+
+          "Exact" is generally preferred but for some languages/projects, you
+          may need a different version of your language server per-project, in
+          which case, "path" will allow you to do so.
+
+          You can modify this behavior per-language by modifying
+          {option}`vim.lsp.servers.*.cmd`.
+        '';
+      };
     };
   };
 

modules/plugins/lsp/presets/haskell-language-server.nix

@@ -6,8 +6,21 @@
 }: let
   inherit (lib.modules) mkIf;
   inherit (lib.nvim.types) mkLspPresetEnableOption;
+  inherit (lib.lists) optional;
   inherit (lib.meta) getExe;
 
+  vendored = getExe (pkgs.symlinkJoin {
+    name = "haskell-language-server-wrapper";
+    paths = [pkgs.haskellPackages.haskell-language-server];
+    meta.mainProgram = "haskell-language-server-wrapper";
+    buildInputs = [pkgs.makeBinaryWrapper];
+    # wrap HLS-wrapper so it can find the actual binary
+    postBuild = ''
+      wrapProgram $out/bin/haskell-language-server-wrapper \
+        --prefix PATH : ${pkgs.haskellPackages.haskell-language-server}/bin
+    '';
+  });
+
   cfg = config.vim.lsp.presets.haskell-language-server;
 in {
   options.vim.lsp.presets.haskell-language-server = {
@@ -21,20 +34,18 @@ in {
     vim.lsp.servers.haskell-language-server = {
       enable = true;
       cmd = [
-        (getExe (pkgs.symlinkJoin {
-          name = "haskell-language-server-wrapper";
-          paths = [pkgs.haskellPackages.haskell-language-server];
-          meta.mainProgram = "haskell-language-server-wrapper";
-          buildInputs = [pkgs.makeBinaryWrapper];
-          # wrap HLS-wrapper so it can find the actual binary
-          postBuild = ''
-            wrapProgram $out/bin/haskell-language-server-wrapper \
-              --prefix PATH : ${pkgs.haskellPackages.haskell-language-server}/bin
-          '';
-        }))
+        (
+          if config.vim.lsp.vendorPrograms == "exact"
+          then vendored
+          else "haskell-language-server-wrapper"
+        )
         "--lsp"
       ];
       root_markers = ["hie.yaml" "stack.yaml" "cabal.project" "*.cabal" "package.yaml"];
     };
+
+    vim.extraPackages =
+      optional (config.vim.lsp.vendorPrograms == "path")
+      pkgs.haskellPackages.haskell-language-server;
   };
 }