feat(bitbucket): add support for ETag at BitbucketUrlReader.readUrl

Signed-off-by: Patrick Jungermann <Patrick.Jungermann@gmail.com>

.changeset/metal-glasses-join.md

@@ -0,0 +1,5 @@
+---
+'@backstage/backend-common': patch
+---
+
+add support for ETag at `BitbucketUrlReader.readUrl`

packages/backend-common/src/reading/BitbucketUrlReader.test.ts

@@ -75,20 +75,74 @@ describe('BitbucketUrlReader', () => {
   setupRequestMockHandlers(worker);
 
   describe('readUrl', () => {
-    worker.use(
-      rest.get(
-        'https://api.bitbucket.org/2.0/repositories/backstage-verification/test-template/src/master/template.yaml',
-        (_, res, ctx) => res(ctx.status(200), ctx.body('foo')),
-      ),
-    );
+    it('should be able to readUrl without ETag', async () => {
+      worker.use(
+        rest.get(
+          'https://api.bitbucket.org/2.0/repositories/backstage-verification/test-template/src/master/template.yaml',
+          (req, res, ctx) => {
+            expect(req.headers.get('If-None-Match')).toBeNull();
+            return res(
+              ctx.status(200),
+              ctx.body('foo'),
+              ctx.set('ETag', 'etag-value'),
+            );
+          },
+        ),
+      );
 
-    it('should be able to readUrl', async () => {
       const result = await bitbucketProcessor.readUrl(
         'https://bitbucket.org/backstage-verification/test-template/src/master/template.yaml',
       );
       const buffer = await result.buffer();
       expect(buffer.toString()).toBe('foo');
     });
+
+    it('should be able to readUrl with matching ETag', async () => {
+      worker.use(
+        rest.get(
+          'https://api.bitbucket.org/2.0/repositories/backstage-verification/test-template/src/master/template.yaml',
+          (req, res, ctx) => {
+            expect(req.headers.get('If-None-Match')).toBe(
+              'matching-etag-value',
+            );
+            return res(ctx.status(304));
+          },
+        ),
+      );
+
+      await expect(
+        bitbucketProcessor.readUrl(
+          'https://bitbucket.org/backstage-verification/test-template/src/master/template.yaml',
+          { etag: 'matching-etag-value' },
+        ),
+      ).rejects.toThrow(NotModifiedError);
+    });
+
+    it('should be able to readUrl without matching ETag', async () => {
+      worker.use(
+        rest.get(
+          'https://api.bitbucket.org/2.0/repositories/backstage-verification/test-template/src/master/template.yaml',
+          (req, res, ctx) => {
+            expect(req.headers.get('If-None-Match')).toBe(
+              'previous-etag-value',
+            );
+            return res(
+              ctx.status(200),
+              ctx.body('foo'),
+              ctx.set('ETag', 'new-etag-value'),
+            );
+          },
+        ),
+      );
+
+      const result = await bitbucketProcessor.readUrl(
+        'https://bitbucket.org/backstage-verification/test-template/src/master/template.yaml',
+        { etag: 'previous-etag-value' },
+      );
+      const buffer = await result.buffer();
+      expect(buffer.toString()).toBe('foo');
+      expect(result.etag).toBe('new-etag-value');
+    });
   });
 
   describe('read', () => {

packages/backend-common/src/reading/BitbucketUrlReader.ts

@@ -80,15 +80,17 @@ export class BitbucketUrlReader implements UrlReader {
     url: string,
     options?: ReadUrlOptions,
   ): Promise<ReadUrlResponse> {
-    // TODO: etag is not supported yet
-    const { signal } = options ?? {};
+    const { etag, signal } = options ?? {};
     const bitbucketUrl = getBitbucketFileFetchUrl(url, this.integration.config);
     const requestOptions = getBitbucketRequestOptions(this.integration.config);
 
     let response: Response;
     try {
       response = await fetch(bitbucketUrl.toString(), {
-        ...requestOptions,
+        headers: {
+          ...requestOptions.headers,
+          ...(etag && { 'If-None-Match': etag }),
+        },
         // TODO(freben): The signal cast is there because pre-3.x versions of
         // node-fetch have a very slightly deviating AbortSignal type signature.
         // The difference does not affect us in practice however. The cast can be
@@ -101,9 +103,14 @@ export class BitbucketUrlReader implements UrlReader {
       throw new Error(`Unable to read ${url}, ${e}`);
     }
 
+    if (response.status === 304) {
+      throw new NotModifiedError();
+    }
+
     if (response.ok) {
       return {
         buffer: async () => Buffer.from(await response.arrayBuffer()),
+        etag: response.headers.get('ETag') ?? undefined,
       };
     }