fix(lsp): omit null diagnostic request fields

CHANGELOG.md

@@ -26,6 +26,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - **ServerCancelled retry** — `LspClient::request()` now retries up to 3 times with exponential backoff (500 ms → 1 s → 2 s) when an LSP server returns error code -32802 with `data.retriggerRequest: true`, instead of propagating the error immediately to the MCP caller (#128)
 - **Integration test readiness gate** — Replaced `publishDiagnostics`-based readiness signal with hover-probe polling (3 consecutive successful hover responses required), matching the ra_e2e approach; fixes 3 of 5 integration tests that failed consistently in isolation after PR #123 (#127)
 - **LSP server requests** — Handle server-to-client requests such as `client/registerCapability`, fixing tsgo timeouts.
+- **Pull diagnostics** — Omit absent `identifier` and `previousResultId` fields from `textDocument/diagnostic` requests, fixing tsgo `InvalidParams` errors.
 - **Integration tests** — Add `[workspace]` table to `tests/fixtures/rust_workspace/Cargo.toml` so cargo treats the fixture as a standalone workspace; fixes 8 rust-analyzer integration tests that failed with "Failed to load workspaces." (#118)
 - **e2e coverage** — Add ra_e2e sub-cases for `get_signature_help`, `go_to_implementation`, `go_to_type_definition`, `get_inlay_hints` (4 LSP 3.17 tools from #124 had no coverage); add `list_resources`, `read_resource`, `subscribe_resource`, `unsubscribe_resource` to `McpClient` and ra_e2e_suite (MCP resources path was entirely untested) (#129, #130)
 

crates/mcpls-core/src/bridge/translator.rs

@@ -116,6 +116,30 @@ impl Default for Translator {
     }
 }
 
+#[derive(Debug, Serialize)]
+#[serde(rename_all = "camelCase")]
+struct DiagnosticRequestParams {
+    text_document: TextDocumentIdentifier,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    identifier: Option<String>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    previous_result_id: Option<String>,
+    #[serde(flatten)]
+    work_done_progress_params: WorkDoneProgressParams,
+    #[serde(flatten)]
+    partial_result_params: PartialResultParams,
+}
+
+fn diagnostic_request_params(text_document: TextDocumentIdentifier) -> DiagnosticRequestParams {
+    DiagnosticRequestParams {
+        text_document,
+        identifier: None,
+        previous_result_id: None,
+        work_done_progress_params: WorkDoneProgressParams::default(),
+        partial_result_params: PartialResultParams::default(),
+    }
+}
+
 /// Position in a document (1-based for MCP).
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct Position2D {
@@ -750,13 +774,7 @@ impl Translator {
             .ensure_open(&validated_path, &client)
             .await?;
 
-        let params = lsp_types::DocumentDiagnosticParams {
-            text_document: TextDocumentIdentifier { uri },
-            identifier: None,
-            previous_result_id: None,
-            work_done_progress_params: WorkDoneProgressParams::default(),
-            partial_result_params: PartialResultParams::default(),
-        };
+        let params = diagnostic_request_params(TextDocumentIdentifier { uri });
 
         let timeout_duration = Duration::from_secs(30);
         let response: lsp_types::DocumentDiagnosticReportResult = client
@@ -2074,6 +2092,17 @@ mod tests {
         // This test verifies the data structure is properly initialized.
     }
 
+    #[test]
+    fn test_diagnostic_request_params_omit_optional_null_fields() {
+        let uri = "file:///test.ts".parse().unwrap();
+        let params = diagnostic_request_params(TextDocumentIdentifier { uri });
+        let value = serde_json::to_value(params).unwrap();
+
+        assert_eq!(value["textDocument"]["uri"], "file:///test.ts");
+        assert!(value.get("identifier").is_none());
+        assert!(value.get("previousResultId").is_none());
+    }
+
     #[test]
     fn test_validate_path_no_workspace_roots() {
         let translator = Translator::new();