What happened?

Both diagnostics(filePath) (single file) and workspaceDiagnostics() (entire workspace) return empty results when using typescript-language-server (and other push-diagnostic-only servers like vtsls).

What did you expect to happen?

After opening a file, both diagnostics() and workspaceDiagnostics() should return diagnostics from the LSP server, just like VS Code does.

Client information

Login information

No response

Anything else we need to know?

Root cause: tsserver only supports the push model (textDocument/publishDiagnostics notifications, LSP 3.16) and does not support the pull model (workspace/diagnostic, textDocument/diagnostic requests, LSP 3.17):

1. workspaceDiagnostics() calls workspace/diagnostic — tsserver throws "not supported", catch block returns nothing.
2. diagnostics(uri) calls textDocument/diagnostic — same failure, same dead catch.
3. The publishDiagnostics capability is not declared in the initialize request, so tsserver never sends diagnostic notifications in the first place.
4. Even if diagnostics were somehow cached, there's no fallback path to read from that cache when the pull model fails.