Add test that fails

src/compiler/program.ts

@@ -936,6 +936,7 @@ namespace ts {
  getOptionsDiagnostics,
  getGlobalDiagnostics,
  getSemanticDiagnostics,
+ getCachedSemanticDiagnostics,
  getSuggestionDiagnostics,
  getDeclarationDiagnostics,
  getBindAndCheckDiagnostics,
@@ -1656,6 +1657,12 @@ namespace ts {
  return getDiagnosticsHelper(sourceFile, getSemanticDiagnosticsForFile, cancellationToken);
  }
 
+ function getCachedSemanticDiagnostics(sourceFile?: SourceFile): readonly Diagnostic[] | undefined {
+ return sourceFile
+ ? cachedBindAndCheckDiagnosticsForFile.perFile?.get(sourceFile.path)
+ : cachedBindAndCheckDiagnosticsForFile.allDiagnostics;
+ }
+
  function getBindAndCheckDiagnostics(sourceFile: SourceFile, cancellationToken?: CancellationToken): readonly Diagnostic[] {
  return getBindAndCheckDiagnosticsForFile(sourceFile, cancellationToken);
  }

src/compiler/types.ts

@@ -3762,6 +3762,8 @@ namespace ts {
  /* @internal */ getDiagnosticsProducingTypeChecker(): TypeChecker;
  /* @internal */ dropDiagnosticsProducingTypeChecker(): void;
 
+ /* @internal */ getCachedSemanticDiagnostics(sourceFile?: SourceFile): readonly Diagnostic[] | undefined;
+
  /* @internal */ getClassifiableNames(): Set<__String>;
 
  getTypeCatalog(): readonly Type[];

src/testRunner/unittests/tscWatch/watchApi.ts

@@ -123,4 +123,36 @@ namespace ts.tscWatch {
  checkProgramActualFiles(watch.getProgram().getProgram(), [mainFile.path, otherFile.path, libFile.path]);
  });
  });
+
+ describe("unittests:: tsc-watch:: watchAPI:: when watchHost uses createSemanticDiagnosticsBuilderProgram", () => {
+ it("verifies that noEmit is handled on createSemanticDiagnosticsBuilderProgram and typechecking happens only on affected files", () => {
+ const config: File = {
+ path: `${projectRoot}/tsconfig.json`,
+ content: "{}"
+ };
+ const mainFile: File = {
+ path: `${projectRoot}/main.ts`,
+ content: "export const x = 10;"
+ };
+ const otherFile: File = {
+ path: `${projectRoot}/other.ts`,
+ content: "export const y = 10;"
+ };
+ const sys = createWatchedSystem([config, mainFile, otherFile, libFile]);
+ const watchCompilerHost = createWatchCompilerHost(
+ config.path,
+ { noEmit: true },
+ sys,
+ createSemanticDiagnosticsBuilderProgram
+ );
+ const watch = createWatchProgram(watchCompilerHost);
+ checkProgramActualFiles(watch.getProgram().getProgram(), [mainFile.path, otherFile.path, libFile.path]);
+ sys.appendFile(mainFile.path, "\n// SomeComment");
+ sys.runQueuedTimeoutCallbacks();
+ const program = watch.getProgram().getProgram();
+ assert.deepEqual(program.getCachedSemanticDiagnostics(program.getSourceFile(mainFile.path)), []);
+ // Should not retrieve diagnostics for other file thats not changed
+ assert.deepEqual(program.getCachedSemanticDiagnostics(program.getSourceFile(otherFile.path)), /*expected*/ undefined);
+ });
+ });
 }