fix(tag-cache): forward isStale() in withFilter (#1189)

The `withFilter` utility did not forward the optional isStale() method
from the underlying tag cache. This broke SWR (stale-while-revalidate)
support added in v1.19.0.

Author: fatihy101

.changeset/major-actors-make.md

@@ -0,0 +1,5 @@
+---
+"@opennextjs/cloudflare": patch
+---
+
+fix(tag-cache): forward `isStale()` in `withFilter`

packages/cloudflare/src/api/overrides/tag-cache/tag-cache-filter.spec.ts

@@ -10,6 +10,7 @@ const mockedTagCache = {
 	getPathsByTags: vi.fn(),
 	hasBeenRevalidated: vi.fn(),
 	writeTags: vi.fn(),
+	isStale: vi.fn(),
 } satisfies NextModeTagCache;
 
 const filterFn = (tag: string) => tag.startsWith("valid_");
@@ -108,6 +109,42 @@ describe("withFilter", () => {
 		expect(tagCache.getPathsByTags).toBeUndefined();
 	});
 
+	it("should filter out tags based on isStale", async () => {
+		const tagCache = withFilter({
+			tagCache: mockedTagCache,
+			filterFn,
+		});
+
+		const tags = ["valid_tag", "invalid_tag"];
+		const lastModified = Date.now();
+
+		await tagCache.isStale?.(tags, lastModified);
+		expect(mockedTagCache.isStale).toHaveBeenCalledWith(["valid_tag"], lastModified);
+	});
+
+	it("should not call isStale if no tags are valid", async () => {
+		const tagCache = withFilter({
+			tagCache: mockedTagCache,
+			filterFn,
+		});
+		const tags = ["invalid_tag"];
+		const lastModified = Date.now();
+		await tagCache.isStale?.(tags, lastModified);
+		expect(mockedTagCache.isStale).not.toHaveBeenCalled();
+	});
+
+	it("should not create a function if isStale is not defined", async () => {
+		const tagCache = withFilter({
+			tagCache: {
+				...mockedTagCache,
+				isStale: undefined,
+			},
+			filterFn,
+		});
+
+		expect(tagCache.isStale).toBeUndefined();
+	});
+
 	it("should filter soft tags", () => {
 		const tagCache = withFilter({
 			tagCache: mockedTagCache,

packages/cloudflare/src/api/overrides/tag-cache/tag-cache-filter.ts

@@ -52,6 +52,15 @@ export function withFilter({ tagCache, filterFn }: WithFilterOptions): NextModeT
 			}
 			return tagCache.writeTags(filteredTags);
 		},
+		isStale: tagCache.isStale
+			? async (tags, lastModified) => {
+					const filteredTags = tags.filter(filterFn);
+					if (filteredTags.length === 0) {
+						return false;
+					}
+					return tagCache.isStale!(filteredTags, lastModified);
+				}
+			: undefined,
 	};
 }