[clangd] Add .cu files to VSCode extension

[ilya-biryukov]

Summary

clangd should be able to handle those with a proper compilation
database. However, users using 'nvcc' might start seeing spurious errors
in '.cu' files after this change.

My plan is to land and release this, but be ready to revert in
case of negative user feedback.

[hokein]

Do we need to add an entry "onLanguage:cuda" for cuda in the extension package.json?

[ilya-biryukov]

In D59759#1441321, @hokein wrote:

Do we need to add an entry "onLanguage:cuda" for cuda in the extension package.json?

Yeah, sounds reasonable, but I don't see cuda in the list of languages in VSCode, nor does it auto-detect a language for .cu files for me.
Can those added by extensions (that I might be missing)? What would be the correct way to lookup all available languages?

[hokein]

In D59759#1441349, @ilya-biryukov wrote:

In D59759#1441321, @hokein wrote:

Do we need to add an entry "onLanguage:cuda" for cuda in the extension package.json?

Yeah, sounds reasonable, but I don't see cuda in the list of languages in VSCode, nor does it auto-detect a language for .cu files for me.
Can those added by extensions (that I might be missing)? What would be the correct way to lookup all available languages?

Taking a closer look, it seems cuda is not supported by default in vscode :(

vscode provides a way to add a new language in the extension, see https://code.visualstudio.com/api/references/contribution-points#contributes.languages, we may define the cuda language in our extension, but vscode also uses this configuration to do other stuff, like syntax highlight, it seems out of scope of our extension, and I'm not sure how would it work with other cuda extension (like vscode-cudacpp which implements the cuda language).

I guess we might leave the patch as it is. clangd won't be started if vscode users only open .cu files; once the users open a c++ file, clangd starts, and clangd should also work for cuda files.

[ilya-biryukov]

In D59759#1441402, @hokein wrote:

Taking a closer look, it seems cuda is not supported by default in vscode :(

vscode provides a way to add a new language in the extension, see https://code.visualstudio.com/api/references/contribution-points#contributes.languages, we may define the cuda language in our extension, but vscode also uses this configuration to do other stuff, like syntax highlight, it seems out of scope of our extension, and I'm not sure how would it work with other cuda extension (like vscode-cudacpp which implements the cuda language).

Agree, we shouldn't define it in our extensions. Actually, IMO the best place for it would be the VSCode code itself. Maybe someone interested in CUDA would pioneer it at some point this and send a PR to VSCode :-)

I guess we might leave the patch as it is. clangd won't be started if vscode users only open .cu files; once the users open a c++ file, clangd starts, and clangd should also work for cuda files.

+1, as annoying as it is, this looks like the best option so far.

[hokein]

clang-tools-extra/clangd/clients/clangd-vscode/src/extension.ts

80–82

nit: worth a comment documenting the behavior of .cu.

[ilya-biryukov]

• Added a comments about CUDA files

clang-tools-extra/clangd/clients/clangd-vscode/src/extension.ts

export function activate(context: vscode.ExtensionContext) {
     };
     const traceFile = getConfig<string>('trace');
     if (!!traceFile) {
         const trace = { CLANGD_TRACE: traceFile };
         clangd.options = { env: { ...process.env, ...trace } };
     }
     const serverOptions: vscodelc.ServerOptions = clangd;
 
+    // Note that CUDA ('.cu') files are special. When opening files of all other
+    // extensions, VSCode would load clangd automatically. This is achieved by
+    // having a corresponding 'onLanguage:...' activation event in package.json.
+    // However, VSCode does not have CUDA as a supported language yet, so we
+    // cannot add a corresponding activationEvent for CUDA files and clangd will
+    // *not* load itself automatically on '.cu' files. When any of the files
+    // with other extensions are open, clangd will load itself and will also
+    // work on '.cu' files.
     const filePattern: string = '**/*.{' +
-        ['cpp', 'c', 'cc', 'cxx', 'c++', 'm', 'mm', 'h', 'hh', 'hpp', 'hxx', 'inc'].join() + '}';
+        ['cpp', 'c', 'cc', 'cu', 'cxx', 'c++', 'm', 'mm',
+            'h', 'hh', 'hpp', 'hxx', 'inc'].join()
+        + '}';
     const clientOptions: vscodelc.LanguageClientOptions = {
         // Register the server for C/C++ files
         documentSelector: [{ scheme: 'file', pattern: filePattern }],
         synchronize: !syncFileEvents ? undefined : {
             fileEvents: vscode.workspace.createFileSystemWatcher(filePattern)
         },
         initializationOptions: { clangdFileStatus: true },
         // Resolve symlinks for all files provided by clangd.