LSP diagnostics not working in Emacs's eglot

[edkolev]

TL;DR: tsgo does not send textDocument/publishDiagnostics to eglot (Emacs LSP implementation).

For comparision, typescript-language-server does send it.

Maybe there's a slight difference in the client capabilities which tsgo expects? Looking at the code I can't identify whether tsgo has some specific expectation for a client capability.

Here's a transcript of the communication eglot <-> LSP server, for both tsgo and `typescript-language-server``: https://gist.github.com/edkolev/c23f5cf03dc66f1efa2de855b5f7d2aa
The transcript is obtained by just opening a .ts file.

IIUC the transcript, tsgo doesn't send textDocument/publishDiagnostics. There seems to be no difference in how eglot presents itself to either server.

Related discussion in eglot's project: joaotavora/eglot#1559

[jakebailey]

We only support pull diagnostics (textDocument/diagnostic, https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#textDocument_pullDiagnostics). Push diagnostics are currently only used for config file errors.

Does eglot not support this?

(It's a significant architectural change to use push diagnostics, which we haven't looked into yet.)