Do not watch the parent folders recursively if not needed.

This avoids watching folders like parent folder of the project root just to watch files created in the folder
Fixes microsoft/vscode#51139

Author: sheetalkamat

src/compiler/resolutionCache.ts

@@ -60,11 +60,14 @@ namespace ts {
         watcher: FileWatcher;
         /** ref count keeping this directory watch alive */
         refCount: number;
+        /** is the directory watched being non recursive */
+        nonRecursive?: boolean;
     }
 
     interface DirectoryOfFailedLookupWatch {
         dir: string;
         dirPath: Path;
+        nonRecursive?: boolean;
         ignore?: true;
     }
 
@@ -251,7 +254,6 @@ namespace ts {
                 perDirectoryResolution = createMap();
                 perDirectoryCache.set(dirPath, perDirectoryResolution);
             }
-
             const resolvedModules: R[] = [];
             const compilerOptions = resolutionHost.getCompilationSettings();
             const hasInvalidatedNonRelativeUnresolvedImport = logChanges && isFileWithInvalidatedNonRelativeUnresolvedImports(path);
@@ -393,6 +395,7 @@ namespace ts {
 
         function getDirectoryToWatchFailedLookupLocation(failedLookupLocation: string, failedLookupLocationPath: Path): DirectoryOfFailedLookupWatch {
             if (isInDirectoryPath(rootPath, failedLookupLocationPath)) {
+                // Always watch root directory recursively
                 return { dir: rootDir!, dirPath: rootPath }; // TODO: GH#18217
             }
 
@@ -409,11 +412,12 @@ namespace ts {
                 dirPath = getDirectoryPath(dirPath);
             }
 
-            // If the directory is node_modules use it to watch
+            // If the directory is node_modules use it to watch, always watch it recursively
             if (isNodeModulesDirectory(dirPath)) {
                 return filterFSRootDirectoriesToWatch({ dir, dirPath }, getDirectoryPath(dirPath));
             }
 
+            let nonRecursive = true;
             // Use some ancestor of the root directory
             let subDirectoryPath: Path | undefined, subDirectory: string | undefined;
             if (rootPath !== undefined) {
@@ -422,14 +426,15 @@ namespace ts {
                     if (parentPath === dirPath) {
                         break;
                     }
+                    nonRecursive = false;
                     subDirectoryPath = dirPath;
                     subDirectory = dir;
                     dirPath = parentPath;
                     dir = getDirectoryPath(dir);
                 }
             }
 
-            return filterFSRootDirectoriesToWatch({ dir: subDirectory || dir, dirPath: subDirectoryPath || dirPath }, dirPath);
+            return filterFSRootDirectoriesToWatch({ dir: subDirectory || dir, dirPath: subDirectoryPath || dirPath, nonRecursive }, dirPath);
         }
 
         function isPathWithDefaultFailedLookupExtension(path: Path) {
@@ -452,7 +457,7 @@ namespace ts {
             let setAtRoot = false;
             for (const failedLookupLocation of failedLookupLocations) {
                 const failedLookupLocationPath = resolutionHost.toPath(failedLookupLocation);
-                const { dir, dirPath, ignore } = getDirectoryToWatchFailedLookupLocation(failedLookupLocation, failedLookupLocationPath);
+                const { dir, dirPath, nonRecursive, ignore } = getDirectoryToWatchFailedLookupLocation(failedLookupLocation, failedLookupLocationPath);
                 if (!ignore) {
                     // If the failed lookup location path is not one of the supported extensions,
                     // store it in the custom path
@@ -464,23 +469,25 @@ namespace ts {
                         setAtRoot = true;
                     }
                     else {
-                        setDirectoryWatcher(dir, dirPath);
+                        setDirectoryWatcher(dir, dirPath, nonRecursive);
                     }
                 }
             }
 
             if (setAtRoot) {
+                // This is always recursive
                 setDirectoryWatcher(rootDir!, rootPath); // TODO: GH#18217
             }
         }
 
-        function setDirectoryWatcher(dir: string, dirPath: Path) {
+        function setDirectoryWatcher(dir: string, dirPath: Path, nonRecursive?: boolean) {
             const dirWatcher = directoryWatchesOfFailedLookups.get(dirPath);
             if (dirWatcher) {
+                Debug.assert(!!nonRecursive === !!dirWatcher.nonRecursive);
                 dirWatcher.refCount++;
             }
             else {
-                directoryWatchesOfFailedLookups.set(dirPath, { watcher: createDirectoryWatcher(dir, dirPath), refCount: 1 });
+                directoryWatchesOfFailedLookups.set(dirPath, { watcher: createDirectoryWatcher(dir, dirPath, nonRecursive), refCount: 1, nonRecursive });
             }
         }
 
@@ -530,7 +537,7 @@ namespace ts {
             dirWatcher.refCount--;
         }
 
-        function createDirectoryWatcher(directory: string, dirPath: Path) {
+        function createDirectoryWatcher(directory: string, dirPath: Path, nonRecursive: boolean | undefined) {
             return resolutionHost.watchDirectoryOfFailedLookupLocation(directory, fileOrDirectory => {
                 const fileOrDirectoryPath = resolutionHost.toPath(fileOrDirectory);
                 if (cachedDirectoryStructureHost) {
@@ -541,7 +548,7 @@ namespace ts {
                 if (!allFilesHaveInvalidatedResolution && invalidateResolutionOfFailedLookupLocation(fileOrDirectoryPath, dirPath === fileOrDirectoryPath)) {
                     resolutionHost.onInvalidatedResolution();
                 }
-            }, WatchDirectoryFlags.Recursive);
+            }, nonRecursive ? WatchDirectoryFlags.None : WatchDirectoryFlags.Recursive);
         }
 
         function removeResolutionsOfFileFromCache(cache: Map<Map<ResolutionWithFailedLookupLocations>>, filePath: Path) {

src/testRunner/unittests/tsserverProjectSystem.ts

@@ -8011,10 +8011,10 @@ new C();`
                 checkCompleteEvent(session, 2, expectedSequenceId);
             }
 
-            function verifyWatchedFilesAndDirectories(host: TestServerHost, files: string[], directories: string[]) {
+            function verifyWatchedFilesAndDirectories(host: TestServerHost, files: string[], recursiveDirectories: string[], nonRecursiveDirectories: string[]) {
                 checkWatchedFilesDetailed(host, files.filter(f => f !== recognizersDateTimeSrcFile.path), 1);
-                checkWatchedDirectories(host, emptyArray, /*recursive*/ false);
-                checkWatchedDirectoriesDetailed(host, directories, 1, /*recursive*/ true);
+                checkWatchedDirectoriesDetailed(host, nonRecursiveDirectories, 1,  /*recursive*/ false);
+                checkWatchedDirectoriesDetailed(host, recursiveDirectories, 1, /*recursive*/ true);
             }
 
             function createSessionAndOpenFile(host: TestServerHost) {
@@ -8035,22 +8035,23 @@ new C();`
                     const filesWithNodeModulesSetup = [...filesWithSources, nodeModulesRecorgnizersText];
                     const filesAfterCompilation = [...filesWithNodeModulesSetup, recongnizerTextDistTypingFile];
 
-                    const watchedDirectoriesWithResolvedModule = [`${recognizersDateTime}/src`, withPathMapping ? packages : recognizersDateTime, ...getTypeRootsFromLocation(recognizersDateTime)];
+                    const watchedDirectoriesWithResolvedModule = [`${recognizersDateTime}/src`, ...(withPathMapping ? emptyArray : [recognizersDateTime]), ...getTypeRootsFromLocation(recognizersDateTime)];
                     const watchedDirectoriesWithUnresolvedModule = [recognizersDateTime, ...(withPathMapping ? [recognizersText] : emptyArray), ...watchedDirectoriesWithResolvedModule, ...getNodeModuleDirectories(packages)];
+                    const nonRecursiveWatchedDirectories = withPathMapping ? [packages] : emptyArray;
 
                     function verifyProjectWithResolvedModule(session: TestSession) {
                         const projectService = session.getProjectService();
                         const project = projectService.configuredProjects.get(recognizerDateTimeTsconfigPath)!;
                         checkProjectActualFiles(project, filesInProjectWithResolvedModule);
-                        verifyWatchedFilesAndDirectories(session.host, filesInProjectWithResolvedModule, watchedDirectoriesWithResolvedModule);
+                        verifyWatchedFilesAndDirectories(session.host, filesInProjectWithResolvedModule, watchedDirectoriesWithResolvedModule, nonRecursiveWatchedDirectories);
                         verifyErrors(session, []);
                     }
 
                     function verifyProjectWithUnresolvedModule(session: TestSession) {
                         const projectService = session.getProjectService();
                         const project = projectService.configuredProjects.get(recognizerDateTimeTsconfigPath)!;
                         checkProjectActualFiles(project, filesInProjectWithUnresolvedModule);
-                        verifyWatchedFilesAndDirectories(session.host, filesInProjectWithUnresolvedModule, watchedDirectoriesWithUnresolvedModule);
+                        verifyWatchedFilesAndDirectories(session.host, filesInProjectWithUnresolvedModule, watchedDirectoriesWithUnresolvedModule, nonRecursiveWatchedDirectories);
                         const startOffset = recognizersDateTimeSrcFile.content.indexOf('"') + 1;
                         verifyErrors(session, [
                             createDiagnostic({ line: 1, offset: startOffset }, { line: 1, offset: startOffset + moduleNameInFile.length }, Diagnostics.Cannot_find_module_0, [moduleName])
@@ -8557,11 +8558,10 @@ export const x = 10;`
             service.openClientFile(srcFile.path, srcFile.content, ScriptKind.TS, projectRoot);
             checkProjectActualFiles(service.configuredProjects.get(configFile.path)!, files.map(f => f.path));
             checkWatchedFilesDetailed(host, mapDefined(files, f => f === srcFile ? undefined : f.path), 1);
-            checkWatchedDirectories(host, emptyArray, /*recursive*/ false);
+            checkWatchedDirectoriesDetailed(host, [`${projectRoot}`], 1,  /*recursive*/ false); // failed lookup for fs
             const expectedWatchedDirectories = createMap<number>();
             expectedWatchedDirectories.set(`${projectRoot}/src`, 2); // Wild card and failed lookup
             expectedWatchedDirectories.set(`${projectRoot}/somefolder`, 1); // failed lookup for somefolder/module2
-            expectedWatchedDirectories.set(`${projectRoot}`, 1); // failed lookup for fs
             expectedWatchedDirectories.set(`${projectRoot}/node_modules`, 1); // failed lookup for with node_modules/@types/fs
             expectedWatchedDirectories.set(`${projectRoot}/src/typings`, 1); // typeroot directory
             checkWatchedDirectoriesDetailed(host, expectedWatchedDirectories, /*recursive*/ true);