From f8edd059109301758e2b87b18d26dac600fc8c6a Mon Sep 17 00:00:00 2001
From: Lubos <lubos@heyapi.dev>
Date: Sat, 24 Oct 2026 04:38:08 +0800
Subject: [PATCH] Refresh diagnostics when a content-mapped or declaration file
 changes on disk

#64159 changed DidChangeWatchedFiles to read the extension through path.Extension(), which knows only TypeScript's own extensions. A content-mapped file such as shape.data got "" and was treated as a possible directory, so the content mapper extension check was never reached. A .d.ts file got ".d.ts", which isRelevantExtension does not list. Neither change scheduled a diagnostics refresh.

Fixes #64943
---
 tsc/internal/project/contentmapper_test.go | 26 +++++++++++++++
 tsc/internal/project/session.go            |  7 ++--
 tsc/internal/project/session_test.go       | 38 ++++++++++++++++++++++
 3 files changed, 66 insertions(+), 5 deletions(-)

diff --git a/tsc/internal/project/contentmapper_test.go b/tsc/internal/project/contentmapper_test.go
index 95f2da159160a..070cf6b2f3b1f 100644
--- a/tsc/internal/project/contentmapper_test.go
+++ b/tsc/internal/project/contentmapper_test.go
@@ -265,6 +265,32 @@ func TestContentMapperInProject(t *testing.T) {
 		assert.Assert(t, strings.Contains(updated.Text(), "export const watched = true;"), "updated app.box missing watched change: %q", updated.Text())
 	})
 
+	t.Run("watch change to a content-mapped file schedules diagnostics refresh", func(t *testing.T) {
+		t.Parallel()
+		session, utils := newSession(true)
+		defer session.Close()
+
+		ctx := context.Background()
+		mainURI := lsproto.DocumentUri("file:///home/project/main.ts")
+		session.DidOpenFile(ctx, mainURI, 1, files["/home/project/main.ts"].(string), lsproto.LanguageKindTypeScript)
+		_, err := session.GetLanguageService(ctx, mainURI)
+		assert.NilError(t, err)
+		session.WaitForBackgroundTasks()
+
+		baselineRefreshCount := len(utils.Client().RefreshDiagnosticsCalls())
+		assert.NilError(t, utils.FS().WriteFile("/home/project/app.box", "export const version = #{target};\nexport const watched = true;\n"))
+		session.DidChangeWatchedFiles(ctx, []*lsproto.FileEvent{{
+			Uri:  "file:///home/project/app.box",
+			Type: lsproto.FileChangeTypeChanged,
+		}})
+		session.WaitForBackgroundTasks()
+
+		refreshCount := len(utils.Client().RefreshDiagnosticsCalls())
+		assert.Assert(t, refreshCount > baselineRefreshCount,
+			"expected RefreshDiagnostics to be called after app.box changed on disk, got %d calls (baseline %d)",
+			refreshCount, baselineRefreshCount)
+	})
+
 	t.Run("unchanged content-mapped file is reused from the cache across a full rebuild", func(t *testing.T) {
 		t.Parallel()
 		session, utils := newSession(true)
diff --git a/tsc/internal/project/session.go b/tsc/internal/project/session.go
index e02dd45c3e842..d93fa052cf62a 100644
--- a/tsc/internal/project/session.go
+++ b/tsc/internal/project/session.go
@@ -448,7 +448,7 @@ func (s *Session) DidChangeWatchedFiles(ctx context.Context, changes []*lsproto.
 		if !hasRelevantChange {
 			filePath := change.Uri.Path()
 			path := s.caseSensitivity.PathKey(filePath).RemoveTrailingDirectorySeparator()
-			if contentMapperWatchedFiles.Has(path) {
+			if contentMapperWatchedFiles.Has(path) || path.ExtensionIsOneOf(contentMapperExtensions) {
 				hasRelevantChange = true
 				continue
 			}
@@ -468,10 +468,7 @@ func (s *Session) DidChangeWatchedFiles(ctx context.Context, changes []*lsproto.
 					}
 				}
 			} else {
-				if isRelevantExtension(extension) ||
-					path.ExtensionIsOneOf(contentMapperExtensions) {
-					hasRelevantChange = true
-				}
+				hasRelevantChange = true
 			}
 		}
 	}
diff --git a/tsc/internal/project/session_test.go b/tsc/internal/project/session_test.go
index 81199e3731803..1a329db9cde3f 100644
--- a/tsc/internal/project/session_test.go
+++ b/tsc/internal/project/session_test.go
@@ -1081,6 +1081,44 @@ export const value = content;`,
 				refreshCount, baselineRefreshCount)
 		})
 
+		t.Run("change to a declaration file schedules diagnostics refresh", func(t *testing.T) {
+			t.Parallel()
+			files := map[string]any{
+				"/home/projects/TS/p1/tsconfig.json": `{
+					"compilerOptions": {
+						"noLib": true
+					},
+					"files": ["index.ts", "types.d.ts"]
+				}`,
+				"/home/projects/TS/p1/index.ts":   `export const value: Value = 1;`,
+				"/home/projects/TS/p1/types.d.ts": `type Value = string;`,
+			}
+			session, utils := projecttestutil.Setup(files)
+			session.DidOpenFile(context.Background(), "file:///home/projects/TS/p1/index.ts", 1, files["/home/projects/TS/p1/index.ts"].(string), lsproto.LanguageKindTypeScript)
+
+			_, err := session.GetLanguageService(context.Background(), "file:///home/projects/TS/p1/index.ts")
+			assert.NilError(t, err)
+			session.WaitForBackgroundTasks()
+
+			baselineRefreshCount := len(utils.Client().RefreshDiagnosticsCalls())
+
+			err = utils.FS().WriteFile("/home/projects/TS/p1/types.d.ts", `type Value = number;`)
+			assert.NilError(t, err)
+
+			session.DidChangeWatchedFiles(context.Background(), []*lsproto.FileEvent{
+				{
+					Type: lsproto.FileChangeTypeChanged,
+					Uri:  "file:///home/projects/TS/p1/types.d.ts",
+				},
+			})
+			session.WaitForBackgroundTasks()
+
+			refreshCount := len(utils.Client().RefreshDiagnosticsCalls())
+			assert.Assert(t, refreshCount > baselineRefreshCount,
+				"expected RefreshDiagnostics to be called after changing /home/projects/TS/p1/types.d.ts, got %d calls (baseline %d)",
+				refreshCount, baselineRefreshCount)
+		})
+
 		t.Run("delete sibling folder schedules diagnostics refresh after opening third file", func(t *testing.T) {
 			t.Parallel()
 			files := map[string]any{