fix: handle diagnostics object in getEmitOutput

* diagnostics object in ts.EmitOutput is internal but needs to be processed in order to be serializable

src/language/typescript/tsWorker.ts

@@ -405,7 +405,16 @@ export class TypeScriptWorker implements ts.LanguageServiceHost, ITypeScriptWork
  if (fileNameIsLib(fileName)) {
  return { outputFiles: [], emitSkipped: true };
  }
- return this._languageService.getEmitOutput(fileName);
+ const emitOutput = this._languageService.getEmitOutput(fileName);
+
+ // 'diagnostics' object is internal in ts.EmitOutput
+ if ('diagnostics' in emitOutput) {
+ emitOutput.diagnostics = TypeScriptWorker.clearFiles(
+ emitOutput.diagnostics as ts.Diagnostic[]
+ );
+ }
+
+ return emitOutput;
  }
 
  async getCodeFixesAtPosition(