fix(fs): walk does not apply exts filter to directories

fs/walk.ts

@@ -469,7 +469,10 @@ export async function* walk(
   if (exts) {
     exts = exts.map((ext) => ext.startsWith(".") ? ext : `.${ext}`);
   }
-  if (includeDirs && include(root, exts, match, skip)) {
+  // Directories don't have file extensions, so the `exts` filter must not be
+  // applied when deciding whether to yield a directory entry. The `match`
+  // and `skip` regex filters still apply. See #6736.
+  if (includeDirs && include(root, undefined, match, skip)) {
     yield await createWalkEntry(root);
   }
   if (maxDepth < 1 || !include(root, undefined, undefined, skip)) {
@@ -898,7 +901,10 @@ export function* walkSync(
   if (maxDepth < 0) {
     return;
   }
-  if (includeDirs && include(root, exts, match, skip)) {
+  // Directories don't have file extensions, so the `exts` filter must not
+  // be applied when deciding whether to yield a directory entry. The
+  // `match` and `skip` regex filters still apply. See #6736.
+  if (includeDirs && include(root, undefined, match, skip)) {
     yield createWalkEntrySync(root);
   }
   if (maxDepth < 1 || !include(root, undefined, undefined, skip)) {

fs/walk_test.ts

@@ -113,23 +113,42 @@ Deno.test("walkSync() accepts includeFiles option set to false", () =>
     includeFiles: false,
   }));
 
+// `includeDirs` defaults to true, so the root directory entry is also
+// expected. `exts` no longer filters directories (see #6736).
 Deno.test("walk() accepts ext option as strings", async () =>
-  await assertWalkPaths(testdataDir, "ext", ["y.rs", "x.ts"], {
+  await assertWalkPaths(testdataDir, "ext", [".", "y.rs", "x.ts"], {
     exts: [".rs", ".ts"],
   }));
 
 Deno.test("walk() accepts ext option as strings (excluding period prefix)", async () =>
-  await assertWalkPaths(testdataDir, "ext", ["y.rs", "x.ts"], {
+  await assertWalkPaths(testdataDir, "ext", [".", "y.rs", "x.ts"], {
     exts: ["rs", "ts"],
   }));
 
 Deno.test("walkSync() accepts ext option as strings", () =>
-  assertWalkSyncPaths(testdataDir, "ext", ["y.rs", "x.ts"], {
+  assertWalkSyncPaths(testdataDir, "ext", [".", "y.rs", "x.ts"], {
     exts: [".rs", ".ts"],
   }));
 
 Deno.test("walkSync() accepts ext option as strings (excluding period prefix)", () =>
+  assertWalkSyncPaths(testdataDir, "ext", [".", "y.rs", "x.ts"], {
+    exts: [".rs", ".ts"],
+  }));
+
+// https://github.com/denoland/std/issues/6736 — explicit includeDirs:false
+// still drops the directory when an `exts` filter is set. Before the fix,
+// includeDirs:true also dropped it (because the dir name had no extension);
+// after the fix, the dir is yielded as expected (verified by the strings
+// tests above).
+Deno.test("walk() with exts and includeDirs:false yields only files", async () =>
+  await assertWalkPaths(testdataDir, "ext", ["y.rs", "x.ts"], {
+    includeDirs: false,
+    exts: [".rs", ".ts"],
+  }));
+
+Deno.test("walkSync() with exts and includeDirs:false yields only files", () =>
   assertWalkSyncPaths(testdataDir, "ext", ["y.rs", "x.ts"], {
+    includeDirs: false,
     exts: [".rs", ".ts"],
   }));