Clangd

modules/kernels/cpp/default.nix

@@ -4,6 +4,7 @@
 , cling
 , clang
 , xeus-cling
+, llvmPackages
 
 , settings
 , settingsSchema
@@ -17,8 +18,13 @@ with lib;
 let
   attrs = [flavor] ++ settings.interface.attrs;
 
+  kernelName = "cpp";
+
   common = callPackage ../common.nix {};
 
+  languageServers = lib.optionals settings.lsp.clangd.enable
+    [(callPackage ./language_server_clangd { inherit kernelName llvmPackages; })];
+
   displaySuffix = {
     "c++17" = " 17";
     "c++20" = " 20";
@@ -80,10 +86,12 @@ symlinkJoin {
     (callPackage ./kernel_xeus.nix {
       inherit attrs displayName extensions;
       std = flavor;
-      kernelName = "cpp";
+      inherit kernelName;
     })
     cling
-  ];
+  ]
+  ++ languageServers
+  ;
 
   passthru = {
     meta = clang.meta // {
@@ -100,6 +108,7 @@ symlinkJoin {
       clang = clang.version;
       cling = cling.unwrapped.version;
       xeus-cling = xeus-cling.version;
+      clangd = llvmPackages.clang-tools.version;
       std = flavor;
     };
     inherit settings settingsSchema;
@@ -117,6 +126,6 @@ symlinkJoin {
       code_mirror_mode = "clike";
       code_mirror_mime_type = "text/x-c++src";
     };
-    languageServerNames = [];
+    languageServerNames = map (x: x.languageServerName) languageServers;
   };
 }

modules/kernels/cpp/language_server_clangd/default.nix

@@ -0,0 +1,32 @@
+{ lib
+, callPackage
+, llvmPackages
+
+, kernelName
+}:
+
+let
+  common = callPackage ../../common.nix {};
+
+  clangd = llvmPackages.clang-tools;
+
+  languageServerName = "clangd";
+
+  passthru = {
+    inherit languageServerName;
+  };
+
+in
+
+common.writeTextDirWithMetaAndPassthru clangd.meta passthru "lib/codedown/language-servers/cpp-${kernelName}-clangd.yaml" (lib.generators.toYAML {} [{
+  name = languageServerName;
+  version = clangd.version;
+  extensions = ["cpp" "hpp" "cxx" "hxx" "c" "h"];
+  notebook_suffix = ".cpp";
+  attrs = ["cpp"];
+  type = "stream";
+  primary = true;
+  args = [
+    "${clangd}/bin/clangd"
+  ];
+}])

modules/kernels/cpp/module.nix

@@ -57,6 +57,12 @@ in
         type = types.listOf types.str;
         default = ["cpp" "hpp" "cxx" "hxx" "c" "h"];
       };
+
+      lsp.clangd.enable = mkOption {
+        example = "Enable clangd language server";
+        type = types.bool;
+        default = true;
+      };
     };
   };
 

tests/app/Spec/Tests/Cpp.hs

@@ -1,12 +1,15 @@
 {-# LANGUAGE RankNTypes #-}
 {-# OPTIONS_GHC -fno-warn-unused-top-binds #-}
+{-# OPTIONS_GHC -fno-warn-incomplete-uni-patterns #-}
 
 module Spec.Tests.Cpp (tests) where
 
 import Data.String.Interpolate
 import Data.Text
+import Language.LSP.Protocol.Types
 import Test.Sandwich as Sandwich
 import TestLib.JupyterRunnerContext
+import TestLib.LSP
 import TestLib.NixEnvironmentContext
 import TestLib.NixTypes
 import TestLib.TestSearchers
@@ -26,24 +29,47 @@ tests = describe "C++" $ parallel $ do
   tests' "c++23"
   tests' "c++2c"
 
+  testsWithLsp "c++23"
+
 tests' :: Text -> LanguageSpec
 tests' flavor = describe [i|C++ (#{flavor})|] $ introduceNixEnvironment [kernelSpec flavor] [] "C++" $ introduceJupyterRunner $ do
   testKernelStdout "cpp" [__i|\#include <iostream>
                               using namespace std;
                               cout << "hi" << endl;|] "hi\n"
 
+testsWithLsp :: Text -> LanguageSpec
+testsWithLsp flavor = describe [i|C++ (#{flavor}) with LSP|] $ introduceNixEnvironment [kernelSpecWithLsp flavor] [] "C++" $ do
+  describe "LSP" $ do
+    testDiagnostics'' "simple" lsName "test.cpp" (Just "cpp")
+      [__i|int main() {
+             undefined_function();
+             return 0;
+           }|] [] $ \diags -> do
+          info [i|Got diags: #{diags}|]
+          info [i|Got ranges: #{getDiagnosticRanges' diags}|]
+          getDiagnosticRanges' diags `shouldBe` [(Range (Position 1 2) (Position 1 20), Just (InR "undeclared_var_use"), "Use of undeclared identifier 'undefined_function'")]
+
+lsName :: Text
+lsName = "clangd"
 
 kernelSpec :: Text -> NixKernelSpec
-kernelSpec flavor  = NixKernelSpec {
+kernelSpec flavor  = kernelSpec' [[i|flavor = "#{flavor}"|]]
+
+kernelSpecWithLsp :: Text -> NixKernelSpec
+kernelSpecWithLsp flavor = kernelSpec' [
+  [i|flavor = "#{flavor}"|]
+    , "lsp.clangd.enable = true"
+    ]
+
+kernelSpec' :: [Text] -> NixKernelSpec
+kernelSpec' extraConfig = NixKernelSpec {
   nixKernelName = "cpp"
   , nixKernelChannel = "codedown"
   , nixKernelDisplayName = Just "CPP"
   , nixKernelPackages = []
   , nixKernelMeta = Nothing
   , nixKernelIcon = Nothing
-  , nixKernelExtraConfig = Just [
-      [i|flavor = "#{flavor}"|]
-      ]
+  , nixKernelExtraConfig = Just extraConfig
   }
 
 main :: IO ()