fix: retain semantic colors across editable diff updates

tests/lsp.rs

@@ -2357,6 +2357,50 @@ fn lsp_semantics_coalesce_changed_text_and_refresh_without_decoding_stale_payloa
         && frame.get("result").is_some()));
 }
 
+#[test]
+fn lsp_semantic_colors_survive_edits_and_polling_until_a_current_reply() {
+    let fixture = Fixture::new();
+    let mut session = fixture.open("controlled-semantic");
+    until(&mut session, &fixture, |_| {
+        fixture.method_count("textDocument/semanticTokens/full") == 1
+    });
+    semantic_reply(
+        &mut session,
+        &fixture,
+        1,
+        json!({"result": {"data": [0, 0, 1, 4, 0]}}),
+    );
+    let original = session.editor().semantic_tokens().to_vec();
+    assert_eq!(original[0].kind, SemanticTokenKind::Type);
+    session.handle(Input::Char('A'));
+    session.handle(Input::Char('!'));
+    until(&mut session, &fixture, |_| {
+        fixture.method_count("textDocument/semanticTokens/full") == 2
+    });
+    assert_eq!(session.editor().semantic_tokens(), original);
+    session.handle(Input::Char('?'));
+    semantic_reply(
+        &mut session,
+        &fixture,
+        2,
+        json!({"result": {"data": ["stale malformed data"]}}),
+    );
+    until(&mut session, &fixture, |_| {
+        fixture.method_count("textDocument/semanticTokens/full") == 3
+    });
+    assert_eq!(session.editor().semantic_tokens(), original);
+    semantic_reply(
+        &mut session,
+        &fixture,
+        3,
+        json!({"result": {"data": [0, 1, 2, 2, 0]}}),
+    );
+    let tokens = session.editor().semantic_tokens();
+    assert_eq!(tokens[0].kind, SemanticTokenKind::Function);
+    assert_eq!(tokens[0].start, TextPosition { row: 0, column: 1 });
+    assert_eq!(tokens[0].end, TextPosition { row: 0, column: 2 });
+}
+
 #[test]
 fn lsp_semantics_discard_queued_same_revision_rename_and_close_outputs() {
     let fixture = Fixture::new();