Skip typechecking file when generating declaraiton to get d.ts signature for incremental build

src/compiler/checker.ts

@@ -2428,10 +2428,10 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
         return visitEachChild(node, markAsSynthetic, /*context*/ undefined);
     }
 
-    function getEmitResolver(sourceFile: SourceFile, cancellationToken: CancellationToken) {
+    function getEmitResolver(sourceFile: SourceFile, cancellationToken: CancellationToken, forceDtsEmit?: boolean) {
         // Ensure we have all the type information in place for this file so that all the
         // emitter questions of this resolver will return the right information.
-        getDiagnostics(sourceFile, cancellationToken);
+        if (!forceDtsEmit) getDiagnostics(sourceFile, cancellationToken);
         return emitResolver;
     }
 

src/compiler/emitter.ts

@@ -848,7 +848,7 @@ export function emitFiles(resolver: EmitResolver, host: EmitHost, targetSourceFi
         const filesForEmit = forceDtsEmit ? sourceFiles : filter(sourceFiles, isSourceFileNotJson);
         // Setup and perform the transformation to retrieve declarations from the input files
         const inputListOrBundle = compilerOptions.outFile ? [factory.createBundle(filesForEmit)] : filesForEmit;
-        if ((emitOnly && !getEmitDeclarations(compilerOptions)) || compilerOptions.noCheck) {
+        if ((emitOnly && !getEmitDeclarations(compilerOptions)) || compilerOptions.noCheck || forceDtsEmit) {
             // Checker wont collect the linked aliases since thats only done when declaration is enabled and checking is performed.
             // Do that here when emitting only dts files
             filesForEmit.forEach(collectLinkedAliases);

src/compiler/program.ts

@@ -2870,18 +2870,27 @@ export function createProgram(rootNamesOrOptions: readonly string[] | CreateProg
         // This is because in the -out scenario all files need to be emitted, and therefore all
         // files need to be type checked. And the way to specify that all files need to be type
         // checked is to not pass the file to getEmitResolver.
-        const emitResolver = getTypeChecker().getEmitResolver(options.outFile ? undefined : sourceFile, cancellationToken);
+        const typeChecker = getTypeChecker();
+        const emitResolver = typeChecker.getEmitResolver(
+            options.outFile ? undefined : sourceFile,
+            cancellationToken,
+            forceDtsEmit,
+        );
 
         performance.mark("beforeEmit");
 
-        const emitResult = emitFiles(
-            emitResolver,
-            getEmitHost(writeFileCallback),
-            sourceFile,
-            getTransformers(options, customTransformers, emitOnly),
-            emitOnly,
-            /*onlyBuildInfo*/ false,
-            forceDtsEmit,
+        const emitResult = typeChecker.runWithCancellationToken(
+            cancellationToken,
+            () =>
+                emitFiles(
+                    emitResolver,
+                    getEmitHost(writeFileCallback),
+                    sourceFile,
+                    getTransformers(options, customTransformers, emitOnly),
+                    emitOnly,
+                    /*onlyBuildInfo*/ false,
+                    forceDtsEmit,
+                ),
         );
 
         performance.mark("afterEmit");

src/compiler/types.ts

@@ -5264,7 +5264,7 @@ export interface TypeChecker {
     // Should not be called directly.  Should only be accessed through the Program instance.
     /** @internal */ getDiagnostics(sourceFile?: SourceFile, cancellationToken?: CancellationToken): Diagnostic[];
     /** @internal */ getGlobalDiagnostics(): Diagnostic[];
-    /** @internal */ getEmitResolver(sourceFile?: SourceFile, cancellationToken?: CancellationToken): EmitResolver;
+    /** @internal */ getEmitResolver(sourceFile?: SourceFile, cancellationToken?: CancellationToken, forceDts?: boolean): EmitResolver;
 
     /** @internal */ getNodeCount(): number;
     /** @internal */ getIdentifierCount(): number;
@@ -5354,6 +5354,8 @@ export interface TypeChecker {
      * and the operation is cancelled, then it should be discarded, otherwise it is safe to keep.
      */
     runWithCancellationToken<T>(token: CancellationToken, cb: (checker: TypeChecker) => T): T;
+    /**@internal */
+    runWithCancellationToken<T>(token: CancellationToken | undefined, cb: (checker: TypeChecker) => T): T; // eslint-disable-line @typescript-eslint/unified-signatures
 
     /** @internal */ getLocalTypeParametersOfClassOrInterfaceOrTypeAlias(symbol: Symbol): readonly TypeParameter[] | undefined;
     /** @internal */ isDeclarationVisible(node: Declaration | AnyImportSyntax): boolean;

src/testRunner/unittests/tsc/cancellationToken.ts

@@ -17,7 +17,7 @@ import {
     libFile,
 } from "../helpers/virtualFileSystemWithWatch.js";
 
-describe("unittests:: tsc:: builder cancellationToken", () => {
+describe("unittests:: tsc:: builder cancellationToken::", () => {
     verifyCancellation(/*useBuildInfo*/ true, "when emitting buildInfo");
     verifyCancellation(/*useBuildInfo*/ false, "when using state");
     function verifyCancellation(useBuildInfo: boolean, scenario: string) {
@@ -41,9 +41,9 @@ describe("unittests:: tsc:: builder cancellationToken", () => {
             const cFile: File = {
                 path: `/user/username/projects/myproject/c.ts`,
                 content: Utils.dedent`
-                    export class C {
+                    export var C = class CReal {
                         d = 1;
-                    }`,
+                    };`,
             };
             const dFile: File = {
                 path: `/user/username/projects/myproject/d.ts`,