[clangd] Add languages as server capabilities

This change adds a list of supported langauges as part of the server
capabilities. This is related to a PR to add HLSL support to the clangd
VSCode plugin (clangd/vscode-clangd#392).

The review there requested advertising HLSL support as a server
capability. Adding a general "languages" capability seemed more
appropriate.

Author: llvm-beanz

clang-tools-extra/clangd/ClangdLSPServer.cpp

@@ -623,6 +623,8 @@ void ClangdLSPServer::onInitialize(const InitializeParams &Params,
       {"clangdInlayHintsProvider", true},
       {"inlayHintProvider", true},
       {"foldingRangeProvider", true},
+      {"languages",
+       {"c", "cpp", "cuda-cpp", "objective-c", "objective-cpp", "hlsl"}},
   };
 
   {

clang-tools-extra/clangd/test/initialize-params.test

@@ -48,6 +48,14 @@
 # CHECK-NEXT:      "implementationProvider": true,
 # CHECK-NEXT:      "inactiveRegionsProvider": true,
 # CHECK-NEXT:      "inlayHintProvider": true,
+# CHECK-NEXT:      "languages": [
+# CHECK-NEXT:        "c",
+# CHECK-NEXT:        "cpp",
+# CHECK-NEXT:        "cuda-cpp",
+# CHECK-NEXT:        "objective-c",
+# CHECK-NEXT:        "objective-cpp",
+# CHECK-NEXT:        "hlsl"
+# CHECK-NEXT:      ],
 # CHECK-NEXT:      "memoryUsageProvider": true,
 # CHECK-NEXT:      "referencesProvider": true,
 # CHECK-NEXT:      "renameProvider": true,