During emit, if shape signature for the file is same as version, then update it with emitted d.ts file

src/compiler/builder.ts

@@ -161,6 +161,8 @@ namespace ts {
          * true if program has been emitted
          */
         programEmitComplete?: true;
+        /** Stores list of files that change signature during emit - test only */
+        filesChangingSignature?: Set<Path>;
     }
 
     function hasSameKeys(map1: ReadonlyCollection<string> | undefined, map2: ReadonlyCollection<string> | undefined): boolean {
@@ -1150,7 +1152,9 @@ namespace ts {
                 // Otherwise just affected file
                 Debug.checkDefined(state.program).emit(
                     affected === state.program ? undefined : affected as SourceFile,
-                    writeFile || maybeBind(host, host.writeFile),
+                    affected !== state.program && getEmitDeclarations(state.compilerOptions) && !customTransformers ?
+                    getWriteFileUpdatingSignatureCallback(writeFile) :
+                        writeFile || maybeBind(host, host.writeFile),
                     cancellationToken,
                     emitOnlyDtsFiles || emitKind === BuilderFileEmit.DtsOnly,
                     customTransformers
@@ -1161,6 +1165,34 @@ namespace ts {
             );
         }
 
+        function getWriteFileUpdatingSignatureCallback(writeFile: WriteFileCallback | undefined): WriteFileCallback {
+            return (fileName, text, writeByteOrderMark, onError, sourceFiles, data) => {
+                if (isDeclarationFileName(fileName)) {
+                    Debug.assert(sourceFiles?.length === 1);
+                    const file = sourceFiles[0];
+                    const info = state.fileInfos.get(file.resolvedPath)!;
+                    const signature = state.currentAffectedFilesSignatures?.get(file.resolvedPath) || info.signature;
+                    if (signature === file.version) {
+                        const newSignature = (computeHash || generateDjb2Hash)(data?.sourceMapUrlPos !== undefined ? text.substring(0, data.sourceMapUrlPos) : text);
+                        if (newSignature !== file.version) { // Update it
+                            if (host.storeFilesChangingSignatureDuringEmit) (state.filesChangingSignature ||= new Set()).add(file.resolvedPath);
+                            if (state.exportedModulesMap) BuilderState.updateExportedModules(file, file.exportedModulesFromDeclarationEmit, state.currentAffectedFilesExportedModulesMap ||= BuilderState.createManyToManyPathMap());
+                            if (state.affectedFiles && state.affectedFilesIndex! < state.affectedFiles.length) {
+                                state.currentAffectedFilesSignatures!.set(file.resolvedPath, newSignature);
+                            }
+                            else {
+                                info.signature = newSignature;
+                                if (state.exportedModulesMap) BuilderState.updateExportedFilesMapFromCache(state, state.currentAffectedFilesExportedModulesMap);
+                            }
+                        }
+                    }
+                }
+                if (writeFile) writeFile(fileName, text, writeByteOrderMark, onError, sourceFiles, data);
+                else if (host.writeFile) host.writeFile(fileName, text, writeByteOrderMark, onError, sourceFiles, data);
+                else state.program!.writeFile(fileName, text, writeByteOrderMark, onError, sourceFiles, data);
+            };
+        }
+
         /**
          * Emits the JavaScript and declaration files.
          * When targetSource file is specified, emits the files corresponding to that source file,
@@ -1215,7 +1247,15 @@ namespace ts {
                     }
                 }
             }
-            return Debug.checkDefined(state.program).emit(targetSourceFile, writeFile || maybeBind(host, host.writeFile), cancellationToken, emitOnlyDtsFiles, customTransformers);
+            return Debug.checkDefined(state.program).emit(
+                targetSourceFile,
+                !outFile(state.compilerOptions) && getEmitDeclarations(state.compilerOptions) && !customTransformers ?
+                    getWriteFileUpdatingSignatureCallback(writeFile) :
+                    writeFile || maybeBind(host, host.writeFile),
+                cancellationToken,
+                emitOnlyDtsFiles,
+                customTransformers
+            );
         }
 
         /**

src/compiler/builderPublic.ts

@@ -20,6 +20,11 @@ namespace ts {
          */
         /*@internal*/
         disableUseFileVersionAsSignature?: boolean;
+        /**
+         * Store the list of files that update signature during the emit
+         */
+        /*@internal*/
+        storeFilesChangingSignatureDuringEmit?: boolean;
     }
 
     /**

src/compiler/builderState.ts

@@ -450,7 +450,7 @@ namespace ts {
         /**
          * Coverts the declaration emit result into exported modules map
          */
-        function updateExportedModules(sourceFile: SourceFile, exportedModulesFromDeclarationEmit: ExportedModulesFromDeclarationEmit | undefined, exportedModulesMapCache: ManyToManyPathMap) {
+        export function updateExportedModules(sourceFile: SourceFile, exportedModulesFromDeclarationEmit: ExportedModulesFromDeclarationEmit | undefined, exportedModulesMapCache: ManyToManyPathMap) {
             if (!exportedModulesFromDeclarationEmit) {
                 exportedModulesMapCache.deleteKey(sourceFile.resolvedPath);
                 return;

src/compiler/emitter.ts

@@ -531,6 +531,7 @@ namespace ts {
                 printer.writeFile(sourceFile!, writer, sourceMapGenerator);
             }
 
+            let sourceMapUrlPos;
             if (sourceMapGenerator) {
                 if (sourceMapDataList) {
                     sourceMapDataList.push({
@@ -548,6 +549,7 @@ namespace ts {
 
                 if (sourceMappingURL) {
                     if (!writer.isAtStartOfLine()) writer.rawWrite(newLine);
+                    sourceMapUrlPos = writer.getTextPos();
                     writer.writeComment(`//# ${"sourceMappingURL"}=${sourceMappingURL}`); // Tools can sometimes see this line as a source mapping url comment
                 }
 
@@ -562,7 +564,7 @@ namespace ts {
             }
 
             // Write the output file
-            writeFile(host, emitterDiagnostics, jsFilePath, writer.getText(), !!compilerOptions.emitBOM, sourceFiles);
+            writeFile(host, emitterDiagnostics, jsFilePath, writer.getText(), !!compilerOptions.emitBOM, sourceFiles, { sourceMapUrlPos });
 
             // Reset state
             writer.clear();

src/compiler/program.ts

@@ -262,7 +262,7 @@ namespace ts {
             return newValue;
         };
         if (originalWriteFile) {
-            host.writeFile = (fileName, data, writeByteOrderMark, onError, sourceFiles) => {
+            host.writeFile = (fileName, data, ...rest) => {
                 const key = toPath(fileName);
                 fileExistsCache.delete(key);
 
@@ -277,7 +277,7 @@ namespace ts {
                         sourceFileCache.delete(key);
                     }
                 }
-                originalWriteFile.call(host, fileName, data, writeByteOrderMark, onError, sourceFiles);
+                originalWriteFile.call(host, fileName, data, ...rest);
             };
         }
 
@@ -1340,6 +1340,7 @@ namespace ts {
             useCaseSensitiveFileNames: () => host.useCaseSensitiveFileNames(),
             getFileIncludeReasons: () => fileReasons,
             structureIsReused,
+            writeFile,
         };
 
         onProgramCreateComplete();
@@ -1894,8 +1895,7 @@ namespace ts {
                 getProjectReferenceRedirect,
                 isSourceOfProjectReferenceRedirect,
                 getSymlinkCache,
-                writeFile: writeFileCallback || (
-                    (fileName, data, writeByteOrderMark, onError, sourceFiles) => host.writeFile(fileName, data, writeByteOrderMark, onError, sourceFiles)),
+                writeFile: writeFileCallback || writeFile,
                 isEmitBlocked,
                 readFile: f => host.readFile(f),
                 fileExists: f => {
@@ -1914,6 +1914,17 @@ namespace ts {
             };
         }
 
+        function writeFile(
+            fileName: string,
+            text: string,
+            writeByteOrderMark: boolean,
+            onError?: (message: string) => void,
+            sourceFiles?: readonly SourceFile[],
+            data?: WriteFileCallbackData
+        ) {
+            host.writeFile(fileName, text, writeByteOrderMark, onError, sourceFiles, data);
+        }
+
         function emitBuildInfo(writeFileCallback?: WriteFileCallback): EmitResult {
             Debug.assert(!outFile(options));
             tracing?.push(tracing.Phase.Emit, "emitBuildInfo", {}, /*separateBeginAndEnd*/ true);

src/compiler/sys.ts

@@ -1210,11 +1210,13 @@ namespace ts {
         base64decode?(input: string): string;
         base64encode?(input: string): string;
         /*@internal*/ bufferFrom?(input: string, encoding?: string): Buffer;
+        /*@internal*/ require?(baseDir: string, moduleName: string): RequireResult;
+        /*@internal*/ defaultWatchFileKind?(): WatchFileKind | undefined;
+
         // For testing
         /*@internal*/ now?(): Date;
         /*@internal*/ disableUseFileVersionAsSignature?: boolean;
-        /*@internal*/ require?(baseDir: string, moduleName: string): RequireResult;
-        /*@internal*/ defaultWatchFileKind?(): WatchFileKind | undefined;
+        /*@internal*/ storeFilesChangingSignatureDuringEmit?: boolean;
     }
 
     export interface FileWatcher {

src/compiler/types.ts

@@ -3856,12 +3856,16 @@ namespace ts {
      */
     export type ResolvedConfigFileName = string & { _isResolvedConfigFileName: never };
 
+    export interface WriteFileCallbackData {
+        /*@internal*/ sourceMapUrlPos?: number;
+    }
     export type WriteFileCallback = (
         fileName: string,
-        data: string,
+        text: string,
         writeByteOrderMark: boolean,
         onError?: (message: string) => void,
         sourceFiles?: readonly SourceFile[],
+        data?: WriteFileCallbackData,
     ) => void;
 
     export class OperationCanceledException { }
@@ -4067,6 +4071,8 @@ namespace ts {
          * This implementation handles file exists to be true if file is source of project reference redirect when program is created using useSourceOfProjectReferenceRedirect
          */
         /*@internal*/ fileExists(fileName: string): boolean;
+        /** Call compilerHost.writeFile on host program was created with */
+        /*@internal*/ writeFile: WriteFileCallback;
     }
 
     /*@internal*/
@@ -6782,6 +6788,7 @@ namespace ts {
 
         // For testing:
         /*@internal*/ disableUseFileVersionAsSignature?: boolean;
+        /*@internal*/ storeFilesChangingSignatureDuringEmit?: boolean;
     }
 
     /** true if --out otherwise source file name */

src/compiler/utilities.ts

@@ -4459,10 +4459,10 @@ namespace ts {
         return combinePaths(newDirPath, sourceFilePath);
     }
 
-    export function writeFile(host: { writeFile: WriteFileCallback; }, diagnostics: DiagnosticCollection, fileName: string, data: string, writeByteOrderMark: boolean, sourceFiles?: readonly SourceFile[]) {
-        host.writeFile(fileName, data, writeByteOrderMark, hostErrorMessage => {
+    export function writeFile(host: { writeFile: WriteFileCallback; }, diagnostics: DiagnosticCollection, fileName: string, text: string, writeByteOrderMark: boolean, sourceFiles?: readonly SourceFile[], data?: WriteFileCallbackData) {
+        host.writeFile(fileName, text, writeByteOrderMark, hostErrorMessage => {
             diagnostics.add(createCompilerDiagnostic(Diagnostics.Could_not_write_file_0_Colon_1, fileName, hostErrorMessage));
-        }, sourceFiles);
+        }, sourceFiles, data);
     }
 
     function ensureDirectoriesExist(

src/compiler/watch.ts

@@ -573,6 +573,7 @@ namespace ts {
             createHash: maybeBind(host, host.createHash),
             readDirectory: maybeBind(host, host.readDirectory),
             disableUseFileVersionAsSignature: host.disableUseFileVersionAsSignature,
+            storeFilesChangingSignatureDuringEmit: host.storeFilesChangingSignatureDuringEmit,
         };
 
         function writeFile(fileName: string, text: string, writeByteOrderMark: boolean, onError: (message: string) => void) {
@@ -637,6 +638,7 @@ namespace ts {
             createHash: maybeBind(system, system.createHash),
             createProgram: createProgram || createEmitAndSemanticDiagnosticsBuilderProgram as any as CreateProgram<T>,
             disableUseFileVersionAsSignature: system.disableUseFileVersionAsSignature,
+            storeFilesChangingSignatureDuringEmit: system.storeFilesChangingSignatureDuringEmit,
         };
     }
 

src/compiler/watchPublic.ts

@@ -20,6 +20,7 @@ namespace ts {
         const host = createCompilerHostWorker(options, /*setParentNodes*/ undefined, system);
         host.createHash = maybeBind(system, system.createHash);
         host.disableUseFileVersionAsSignature = system.disableUseFileVersionAsSignature;
+        host.storeFilesChangingSignatureDuringEmit = system.storeFilesChangingSignatureDuringEmit;
         setGetSourceFileAsHashVersioned(host, system);
         changeCompilerHostLikeToUseCache(host, fileName => toPath(fileName, host.getCurrentDirectory(), host.getCanonicalFileName));
         return host;
@@ -114,6 +115,7 @@ namespace ts {
         writeFile?(path: string, data: string, writeByteOrderMark?: boolean): void;
         // For testing
         disableUseFileVersionAsSignature?: boolean;
+        storeFilesChangingSignatureDuringEmit?: boolean;
     }
 
     export interface WatchCompilerHost<T extends BuilderProgram> extends ProgramHost<T>, WatchHost {

src/harness/virtualFileSystemWithWatch.ts

@@ -396,6 +396,7 @@ interface Array<T> { length: number; [n: number]: T; }`
         private readonly currentDirectory: string;
         public require: ((initialPath: string, moduleName: string) => RequireResult) | undefined;
         public defaultWatchFileKind?: () => WatchFileKind | undefined;
+        public storeFilesChangingSignatureDuringEmit = true;
         watchFile: HostWatchFile;
         watchDirectory: HostWatchDirectory;
         constructor(

src/testRunner/unittests/tsbuild/outputPaths.ts

@@ -55,16 +55,7 @@ namespace ts {
                     }
                 })
             }),
-            edits: [
-                noChangeRun,
-                {
-                    ...noChangeProject,
-                    cleanBuildDiscrepancies: () => new Map([
-                        ["/src/dist/tsconfig.tsbuildinfo", CleanBuildDescrepancy.CleanFileTextDifferent], // tsbuildinfo will have -p setting when built using -p vs no build happens incrementally because of no change.
-                        ["/src/dist/tsconfig.tsbuildinfo.readable.baseline.txt", CleanBuildDescrepancy.CleanFileTextDifferent] // tsbuildinfo will have -p setting when built using -p vs no build happens incrementally because of no change.
-                    ]),
-                }
-            ],
+            edits,
         }, ["/src/dist/src/index.js", "/src/dist/src/index.d.ts"]);
 
         verify({

src/testRunner/unittests/tsc/helpers.ts

@@ -3,6 +3,7 @@ namespace ts {
         writtenFiles: Set<Path>;
         baseLine(): { file: string; text: string; };
         disableUseFileVersionAsSignature?: boolean;
+        storeFilesChangingSignatureDuringEmit?: boolean;
     };
 
     export const noChangeRun: TestTscEdit = {
@@ -84,6 +85,7 @@ namespace ts {
         // Create system
         const sys = new fakes.System(fs, { executingFilePath: "/lib/tsc", env: environmentVariables }) as TscCompileSystem;
         if (input.disableUseFileVersionAsSignature) sys.disableUseFileVersionAsSignature = true;
+        sys.storeFilesChangingSignatureDuringEmit = true;
         sys.write(`${sys.getExecutingFilePath()} ${commandLineArgs.join(" ")}\n`);
         sys.exit = exitCode => sys.exitCode = exitCode;
         worker(sys);

src/testRunner/unittests/tscWatch/helpers.ts

@@ -336,7 +336,7 @@ namespace ts.tscWatch {
         if (!builderProgram) return;
         if (builderProgram !== oldProgram?.[1]) {
             const state = builderProgram.getState();
-            const internalState = state as unknown as BuilderState;
+            const internalState = state as unknown as BuilderProgramState;
             if (state.semanticDiagnosticsPerFile?.size) {
                 baseline.push("Semantic diagnostics in builder refreshed for::");
                 for (const file of program.getSourceFiles()) {
@@ -354,9 +354,12 @@ namespace ts.tscWatch {
                     baseline.push("Shape signatures in builder refreshed for::");
                     internalState.hasCalledUpdateShapeSignature.forEach((path: Path) => {
                         const info = state.fileInfos.get(path);
-                        if(info?.version === info?.signature || !info?.signature) {
+                        if (info?.version === info?.signature || !info?.signature) {
                             baseline.push(path + " (used version)");
                         }
+                        else if (internalState.filesChangingSignature?.has(path)) {
+                            baseline.push(path + " (computed .d.ts during emit)");
+                        }
                         else {
                             baseline.push(path + " (computed .d.ts)");
                         }

tests/baselines/reference/api/tsserverlibrary.d.ts

@@ -2172,7 +2172,9 @@ declare namespace ts {
     export type ResolvedConfigFileName = string & {
         _isResolvedConfigFileName: never;
     };
-    export type WriteFileCallback = (fileName: string, data: string, writeByteOrderMark: boolean, onError?: (message: string) => void, sourceFiles?: readonly SourceFile[]) => void;
+    export interface WriteFileCallbackData {
+    }
+    export type WriteFileCallback = (fileName: string, text: string, writeByteOrderMark: boolean, onError?: (message: string) => void, sourceFiles?: readonly SourceFile[], data?: WriteFileCallbackData) => void;
     export class OperationCanceledException {
     }
     export interface CancellationToken {

tests/baselines/reference/api/typescript.d.ts

@@ -2172,7 +2172,9 @@ declare namespace ts {
     export type ResolvedConfigFileName = string & {
         _isResolvedConfigFileName: never;
     };
-    export type WriteFileCallback = (fileName: string, data: string, writeByteOrderMark: boolean, onError?: (message: string) => void, sourceFiles?: readonly SourceFile[]) => void;
+    export interface WriteFileCallbackData {
+    }
+    export type WriteFileCallback = (fileName: string, text: string, writeByteOrderMark: boolean, onError?: (message: string) => void, sourceFiles?: readonly SourceFile[], data?: WriteFileCallbackData) => void;
     export class OperationCanceledException {
     }
     export interface CancellationToken {