Is it possible to use Pyright to get semantic tokens for Python?

[MartinThorsen]

Sorry if this is a newbie question.

I am implementing my own simple Python editor and would like to use Pyright to get semantic tokens. I am using OmniSharp.Extensions.LanguageServer to communcate with the language server (LS) From what I can tell by searching, I should initialize the LS as follows:

_lspClient = LanguageClient.PreInit(options =>
{
    options
        // _pyrightProcess is the the result of Process.Start(node.exe, langserver.index.js --stdio)
        .WithInput(_pyrightProcess.StandardOutput.BaseStream)
        .WithOutput(_pyrightProcess.StandardInput.BaseStream)
        .WithInitializationOptions(new{})
        .WithCapability(new SemanticTokensCapability()
        {
            Requests = new SemanticTokensCapabilityRequests
            {
                Full = new Supports<SemanticTokensCapabilityRequestFull>(new SemanticTokensCapabilityRequestFull { Delta = false }),
            },
            TokenTypes = new Container<SemanticTokenType>(SemanticTokenType.Namespace, SemanticTokenType.Class),
        });
});
await _lspClient.Initialize(_cts.Token);

var uri = new Uri("file:///inmemory.py");
_lspClient.TextDocument.DidOpenTextDocument(new DidOpenTextDocumentParams
{
    TextDocument = new TextDocumentItem
    {
        Uri = uri,
        LanguageId = "python",
        Version = 1,
        Text = "import datetime"
    }
});

var semanticTokens = await _lspClient.TextDocument.RequestSemanticTokens(new SemanticTokensParams { TextDocument = new TextDocumentIdentifier(uri) });

However, RequestSemanticTokens returns an OmniSharp.Extensions.JsonRpc.Server.MethodNotSupportedException: 'Method not found: 'textDocument/semanticTokens/full'.'

Is this not supported? Am I missing something?

Thanks.

[Rich Chiodo (rchiodo)]

Semantic tokens are supported by Pylance, not by the open-source Pyright language server. Pyright does not advertise a semanticTokensProvider, so the Method not found: 'textDocument/semanticTokens/full' response is expected.

The Pyright VS Code extension README also calls out semantic token highlighting as one of Pylance's additional capabilities: https://github.com/microsoft/pyright/blob/main/packages/vscode-pyright/README.md#static-type-checker-for-python

There are a few semantic-token references in Pyright's LSP test infrastructure, but those describe client capabilities and refresh handling; they do not implement or register a semantic-token provider.