fix: match weak, list and wildcard for if-none-match file backend

src/storage/backend/file.test.ts

@@ -920,6 +920,19 @@ describe('FileBackend conditional reads', () => {
     await expect(statusFor({ ifNoneMatch: head.eTag })).resolves.toBe(304)
   })
 
+  it.each([
+    ['a weak tag', (eTag: string) => `W/${eTag}`],
+    ['a tag list', (eTag: string) => `"stale-etag", ${eTag}`],
+    ['a wildcard', () => '*'],
+  ])('returns 304 when if-none-match is %s matching the etag', async (_name, toHeader) => {
+    const head = await backend.headObject(bucket, key, version)
+    await expect(statusFor({ ifNoneMatch: toHeader(head.eTag) })).resolves.toBe(304)
+  })
+
+  it('returns 200 when no tag in an if-none-match list matches', async () => {
+    await expect(statusFor({ ifNoneMatch: '"stale-etag", W/"other-etag"' })).resolves.toBe(200)
+  })
+
   it('ignores if-modified-since when if-none-match is present and does not match', async () => {
     await expect(
       statusFor({ ifNoneMatch: '"stale-etag"', ifModifiedSince: lastModifiedHeader })

src/storage/backend/file.ts

@@ -48,6 +48,15 @@ const METADATA_ATTR_KEYS = {
   },
 }
 
+// RFC 9110 13.1.2: "*" matches any current representation;
+// otherwise any listed entity-tag matches under weak comparison.
+function ifNoneMatchMatches(ifNoneMatch: string, eTag: string): boolean {
+  if (ifNoneMatch.trim() === '*') {
+    return true
+  }
+  return ifNoneMatch.split(',').some((tag) => tag.trim().replace(/^W\//, '') === eTag)
+}
+
 /**
  * FileBackend
  * Interacts with the file system with this FileBackend adapter
@@ -101,7 +110,7 @@ export class FileBackend implements StorageBackendAdapter {
     const { cacheControl, contentType } = await this.getFileMetadata(file)
     const lastModified = data.mtime
 
-    if (headers?.ifNoneMatch && headers.ifNoneMatch === eTag) {
+    if (headers?.ifNoneMatch && ifNoneMatchMatches(headers.ifNoneMatch, eTag)) {
       return {
         metadata: {
           cacheControl: cacheControl || 'no-cache',