lsp-custom-requests

# LSP Custom Requests — URI Wire Format ## Why it breaks - `Connection.sendRequest(method, params)` runs `JSON.stringify(params)`. - `vscode-uri` `Uri.toJSON()` returns `UriComponents` (plain data). See [microsoft/vscode-uri src/uri.ts](https://github.com/microsoft/vscode-uri/blob/main/src/uri.ts). - Receiver gets a plain object — no prototype, no `toString`/`fsPath`. - `uri.toString()` → `"[object Object]"` → `fs.stat`/`readFile` fails with `EntryNotFound`. ## Rules - Never call `.toString()` / `.fsPath` on a URI received over the wire without rehydrating first. - Type URI params as `UriComponents` (derived); revive on receive. ## Pattern — UriComponents + revive Params type derived from `URI.toJSON`: ```ts import type { URI } from 'vscode-uri'; type UriComponents = ReturnType<URI['toJSON']>; type MyParams = { uri: UriComponents }; const params: MyParams = { uri: URI.parse(fileUri) }; connection.sendRequest('my/request', params); const handler = (params: MyParams) => { const uri = URI.revive(params.uri); }; ``` Notes: - `vscode-uri`'s package entry does not re-export `UriComponents`; derive via `ReturnType<URI['toJSON']>`. - `URI.revive` is the exact inverse of `toJSON` — restores `_formatted` / `_fsPath` caches too. ## Don't - `uri: URI` on a wire type and use `.toString()` / `.fsPath` on receive — this is the failure mode. - Pass deserialized params straight to `vscode.workspace.fs.*` — those APIs expect a real `URI` instance. ## When `uri: URI` in params looks fine but isn't Compiles cleanly (URI on both sides). Runtime receiver sees a plain `UriComponents`. Check the handler log — `uri=[object Object]` confirms.