fix(project): re-read cached file contents on didChangeWatchedFiles Created event

tsc/internal/project/overlayfs.go

@@ -340,15 +340,13 @@ func (fs *overlayFS) processChanges(changes []FileChange) (FileChangeSummary, ma
 			o = nil
 		}
 
-		if events.watchChanged {
-			if o == nil {
-				result.Changed.Add(uri)
-			} else if o != nil && !events.saved {
-				if matchesDiskText, _ := o.computeMatchesDiskText(fs.fs); matchesDiskText != o.MatchesDiskText() {
-					o = newOverlay(o.FileName(), o.Content(), o.Version(), o.kind)
-					o.matchesDiskText = matchesDiskText
-					newOverlays[path] = o
-				}
+		if events.watchChanged && o == nil {
+			result.Changed.Add(uri)
+		} else if (events.watchChanged || events.created) && o != nil && !events.saved {
+			if matchesDiskText, _ := o.computeMatchesDiskText(fs.fs); matchesDiskText != o.MatchesDiskText() {
+				o = newOverlay(o.FileName(), o.Content(), o.Version(), o.kind)
+				o.matchesDiskText = matchesDiskText
+				newOverlays[path] = o
 			}
 		}
 

tsc/internal/project/overlayfs_test.go

@@ -248,6 +248,39 @@ func TestProcessChanges(t *testing.T) {
 		assert.Assert(t, !fs.getFile(testURI1.FileName()).MatchesDiskText())
 	})
 
+	t.Run("watch create on open overlay updates matchesDiskText", func(t *testing.T) {
+		t.Parallel()
+		fs := createOverlayFS()
+
+		// Open overlay
+		fs.processChanges([]FileChange{
+			{
+				Kind:    FileChangeKindOpen,
+				URI:     testURI1,
+				Content: "overlay content",
+			},
+		})
+		assert.Assert(t, !fs.getFile(testURI1.FileName()).MatchesDiskText())
+
+		// Save overlay (matches disk)
+		fs.processChanges([]FileChange{
+			{
+				Kind: FileChangeKindSave,
+				URI:  testURI1,
+			},
+		})
+		assert.Assert(t, fs.getFile(testURI1.FileName()).MatchesDiskText())
+
+		// Watch create event on disk (e.g. external overwrite)
+		fs.processChanges([]FileChange{
+			{
+				Kind: FileChangeKindWatchCreate,
+				URI:  testURI1,
+			},
+		})
+		assert.Assert(t, !fs.getFile(testURI1.FileName()).MatchesDiskText())
+	})
+
 	t.Run("save without overlay should not panic", func(t *testing.T) {
 		t.Parallel()
 		fs := createOverlayFS()

tsc/internal/project/session_test.go

@@ -659,6 +659,74 @@ func TestSession(t *testing.T) {
 			assert.Check(t, lsAfter.GetProgram() != programBefore)
 		})
 
+		t.Run("create closed program file reloads content (atomic save)", func(t *testing.T) {
+			t.Parallel()
+			files := maps.Clone(defaultFiles)
+			session, utils := projecttestutil.Setup(files)
+
+			session.DidOpenFile(context.Background(), "file:///home/projects/TS/p1/src/index.ts", 1, files["/home/projects/TS/p1/src/index.ts"].(string), lsproto.LanguageKindTypeScript)
+
+			lsBefore, err := session.GetLanguageService(context.Background(), "file:///home/projects/TS/p1/src/index.ts")
+			assert.NilError(t, err)
+			programBefore := lsBefore.GetProgram()
+
+			err = utils.FS().WriteFile("/home/projects/TS/p1/src/x.ts", `export const x = 2;`)
+			assert.NilError(t, err)
+
+			// Simulate atomic save / rename where watcher reports Created (type 1)
+			session.DidChangeWatchedFiles(context.Background(), []*lsproto.FileEvent{
+				{
+					Type: lsproto.FileChangeTypeCreated,
+					Uri:  "file:///home/projects/TS/p1/src/x.ts",
+				},
+			})
+
+			lsAfter, err := session.GetLanguageService(context.Background(), "file:///home/projects/TS/p1/src/index.ts")
+			assert.NilError(t, err)
+			assert.Check(t, lsAfter.GetProgram() != programBefore)
+			srcX := lsAfter.GetProgram().GetSourceFile("/home/projects/TS/p1/src/x.ts")
+			assert.Assert(t, srcX != nil)
+			assert.Equal(t, srcX.Text(), "export const x = 2;")
+		})
+
+		t.Run("atomic save sequence with temp file reloads content", func(t *testing.T) {
+			t.Parallel()
+			files := maps.Clone(defaultFiles)
+			session, utils := projecttestutil.Setup(files)
+
+			session.DidOpenFile(context.Background(), "file:///home/projects/TS/p1/src/index.ts", 1, files["/home/projects/TS/p1/src/index.ts"].(string), lsproto.LanguageKindTypeScript)
+
+			lsBefore, err := session.GetLanguageService(context.Background(), "file:///home/projects/TS/p1/src/index.ts")
+			assert.NilError(t, err)
+			programBefore := lsBefore.GetProgram()
+
+			err = utils.FS().WriteFile("/home/projects/TS/p1/src/x.ts", `export const x = 42;`)
+			assert.NilError(t, err)
+
+			// Sequence sent by editors like VS Code on atomic save: tmp create -> target create -> tmp delete
+			session.DidChangeWatchedFiles(context.Background(), []*lsproto.FileEvent{
+				{
+					Type: lsproto.FileChangeTypeCreated,
+					Uri:  "file:///home/projects/TS/p1/src/x.ts.tmp",
+				},
+				{
+					Type: lsproto.FileChangeTypeCreated,
+					Uri:  "file:///home/projects/TS/p1/src/x.ts",
+				},
+				{
+					Type: lsproto.FileChangeTypeDeleted,
+					Uri:  "file:///home/projects/TS/p1/src/x.ts.tmp",
+				},
+			})
+
+			lsAfter, err := session.GetLanguageService(context.Background(), "file:///home/projects/TS/p1/src/index.ts")
+			assert.NilError(t, err)
+			assert.Check(t, lsAfter.GetProgram() != programBefore)
+			srcX := lsAfter.GetProgram().GetSourceFile("/home/projects/TS/p1/src/x.ts")
+			assert.Assert(t, srcX != nil)
+			assert.Equal(t, srcX.Text(), "export const x = 42;")
+		})
+
 		t.Run("change program file not in tsconfig root files", func(t *testing.T) {
 			t.Parallel()
 			for _, workspaceDir := range []string{"/", "/home/projects/TS/p1", "/somewhere/else/entirely"} {

tsc/internal/project/snapshotfs.go

@@ -445,6 +445,15 @@ func (s *snapshotFSBuilder) watchChangesOverlapCache(change FileChangeSummary) b
 			return true
 		}
 	}
+	for uri := range change.Created.Keys() {
+		path := s.toPath(uri.FileName())
+		if _, ok := s.diskFiles.Load(path); ok {
+			return true
+		}
+		if _, ok := s.nodeModulesRealpathAliases.Load(path); ok {
+			return true
+		}
+	}
 	for uri := range change.Deleted.Keys() {
 		path := s.toPath(uri.FileName())
 		if _, ok := s.diskFiles.Load(path); ok {
@@ -478,33 +487,40 @@ func (s *snapshotFSBuilder) invalidateNodeModulesCache() {
 }
 
 func (s *snapshotFSBuilder) markDirtyFiles(change FileChangeSummary) FileChangeSummary {
-	if change.Changed.Len() > 0 {
-		var filteredChanged collections.SyncSet[lsproto.DocumentUri]
+	filterChanges := func(set collections.Set[lsproto.DocumentUri]) collections.Set[lsproto.DocumentUri] {
+		if set.Len() == 0 {
+			return set
+		}
+		var filtered collections.SyncSet[lsproto.DocumentUri]
 		wg := core.NewWorkGroup(false)
-		for uri := range change.Changed.Keys() {
+		for uri := range set.Keys() {
 			path := s.toPath(uri.FileName())
 			if _, ok := s.overlays[path]; ok {
-				filteredChanged.Add(uri)
+				filtered.Add(uri)
 				continue
 			}
 			entry, ok := s.diskFiles.Load(path)
 			if !ok {
-				filteredChanged.Add(uri)
+				filtered.Add(uri)
 				continue
 			}
 			wg.Queue(func() {
 				if s.reloadEntryIfContentChanged(entry) {
-					filteredChanged.Add(uri)
+					filtered.Add(uri)
 				}
 			})
 		}
 		wg.RunAndWait()
-		newChanged := collections.NewSetWithSizeHint[lsproto.DocumentUri](filteredChanged.Size())
-		for uri := range filteredChanged.Keys() {
-			newChanged.Add(uri)
+		newSet := collections.NewSetWithSizeHint[lsproto.DocumentUri](filtered.Size())
+		for uri := range filtered.Keys() {
+			newSet.Add(uri)
 		}
-		change.Changed = *newChanged
+		return *newSet
 	}
+
+	change.Changed = filterChanges(change.Changed)
+	change.Created = filterChanges(change.Created)
+
 	for uri := range change.Deleted.Keys() {
 		path := s.toPath(uri.FileName())
 		if entry, ok := s.diskFiles.Load(path); ok {
@@ -548,7 +564,7 @@ func (s *snapshotFSBuilder) reloadEntryIfContentChanged(entry *dirty.SyncMapEntr
 	return changed
 }
 
-// expandRealpathAliases adds synthetic URIs to the Changed and Deleted sets for
+// expandRealpathAliases adds synthetic URIs to the Changed, Created, and Deleted sets for
 // files that were accessed through node_modules symlinks. When a watch event arrives
 // using a realpath, this expands it to include the symlink-based path so that
 // downstream consumers (markDirtyFiles, markFilesChanged) can find cached entries.
@@ -557,31 +573,27 @@ func (s *SnapshotFS) expandRealpathAliases(change FileChangeSummary) FileChangeS
 		return change
 	}
 
-	var additionalChanged collections.Set[lsproto.DocumentUri]
-	for uri := range change.Changed.Keys() {
-		path := s.toPath(uri.FileName())
-		if aliases, ok := s.nodeModulesRealpathAliases[path]; ok {
-			for aliasPath := range aliases.paths.Keys() {
-				additionalChanged.Add(lsconv.FileNameToDocumentURI(string(aliasPath)))
-			}
+	expandSet := func(set *collections.Set[lsproto.DocumentUri]) {
+		if set.Len() == 0 {
+			return
 		}
-	}
-	for uri := range additionalChanged.Keys() {
-		change.Changed.Add(uri)
-	}
-
-	var additionalDeleted collections.Set[lsproto.DocumentUri]
-	for uri := range change.Deleted.Keys() {
-		path := s.toPath(uri.FileName())
-		if aliases, ok := s.nodeModulesRealpathAliases[path]; ok {
-			for aliasPath := range aliases.paths.Keys() {
-				additionalDeleted.Add(lsconv.FileNameToDocumentURI(string(aliasPath)))
+		var additional collections.Set[lsproto.DocumentUri]
+		for uri := range set.Keys() {
+			path := s.toPath(uri.FileName())
+			if aliases, ok := s.nodeModulesRealpathAliases[path]; ok {
+				for aliasPath := range aliases.paths.Keys() {
+					additional.Add(lsconv.FileNameToDocumentURI(string(aliasPath)))
+				}
 			}
 		}
+		for uri := range additional.Keys() {
+			set.Add(uri)
+		}
 	}
-	for uri := range additionalDeleted.Keys() {
-		change.Deleted.Add(uri)
-	}
+
+	expandSet(&change.Changed)
+	expandSet(&change.Created)
+	expandSet(&change.Deleted)
 
 	return change
 }

tsc/internal/project/snapshotfs_test.go

@@ -1324,6 +1324,61 @@ func TestRealpathAliasLifecycle(t *testing.T) {
 		assert.Equal(t, file.Content(), `{"name": "mylib"}`, "content should be updated")
 	})
 
+	t.Run("markDirtyFiles invalidates existing cached file on created event", func(t *testing.T) {
+		t.Parallel()
+		testFS := vfstest.FromMap(map[string]any{
+			"/project/src/helper.ts": `export const other = 1;`,
+		}, false)
+
+		// Build first snapshot — read the file.
+		builder1 := newSnapshotFSBuilder(
+			testFS,
+			make(map[tspath.Path]*Overlay),
+			make(map[tspath.Path]*Overlay),
+			make(map[tspath.Path]*diskFile),
+			make(map[tspath.Path]dirty.CloneableMap[tspath.Path, string]),
+			nil,
+			lsproto.PositionEncodingKindUTF16,
+			toPath,
+		)
+		fh := builder1.GetFile("/project/src/helper.ts")
+		assert.Assert(t, fh != nil)
+		assert.Equal(t, fh.Content(), `export const other = 1;`)
+		snapshot1, _ := builder1.Finalize()
+
+		// Modify the file on disk (e.g. via atomic save rename).
+		err := testFS.WriteFile("/project/src/helper.ts", `export const thing = 1;`)
+		assert.NilError(t, err)
+
+		// Build second snapshot — simulate Created event.
+		builder2 := newSnapshotFSBuilder(
+			testFS,
+			make(map[tspath.Path]*Overlay),
+			make(map[tspath.Path]*Overlay),
+			snapshot1.diskFiles,
+			snapshot1.diskDirectories,
+			snapshot1.nodeModulesRealpathAliases,
+			lsproto.PositionEncodingKindUTF16,
+			toPath,
+		)
+
+		change := FileChangeSummary{}
+		change.Created.Add("file:///project/src/helper.ts")
+
+		change = builder2.markDirtyFiles(change)
+		assert.Assert(t, change.Created.Has("file:///project/src/helper.ts"))
+
+		// Reading the file should return the updated content.
+		fh = builder2.GetFile("/project/src/helper.ts")
+		assert.Assert(t, fh != nil)
+		assert.Equal(t, fh.Content(), `export const thing = 1;`)
+
+		snapshot2, _ := builder2.Finalize()
+		file, ok := snapshot2.diskFiles[tspath.Path("/project/src/helper.ts")]
+		assert.Assert(t, ok)
+		assert.Equal(t, file.Content(), `export const thing = 1;`)
+	})
+
 	t.Run("alias clone isolation between snapshots", func(t *testing.T) {
 		t.Parallel()
 		testFS := vfstest.FromMap(map[string]any{