fix: prevent error when stories.json has an invalid format (#794)

fixes #785

Author: fabioatcorreia

packages/visual-service/src/storybook/utils.ts

@@ -112,8 +112,12 @@ export async function getStoriesJson(url: string): Promise<Stories> {
 
         for (const response of [storiesRes, indexRes]) {
             if (response.ok) {
-                const data = await response.json() as StoriesRes | IndexRes
-                return (data as StoriesRes).stories || (data as IndexRes).entries
+                try {
+                    const data = await response.json() as StoriesRes | IndexRes
+                    return (data as StoriesRes).stories || (data as IndexRes).entries
+                } catch (_ign) {
+                    // Ignore the json parse error
+                }
             }
         }
     } catch (_ign) {

packages/visual-service/tests/storybook/utils.test.ts

@@ -216,6 +216,16 @@ describe('Storybook utils', () => {
             expect(data).toEqual(['entry1', 'entry2'])
         })
 
+        it('successfully fetches index entries when stories fetch has an invalid json format', async () => {
+            // @ts-ignore
+            vi.mocked(fetch).mockResolvedValueOnce(new Response(JSON.stringify({ entries: ['entry1', 'entry2'] }), { status: 200 }))
+            // @ts-ignore
+            vi.mocked(fetch).mockResolvedValueOnce(new Response('invalid json', { status: 200 }))
+
+            const data = await getStoriesJson('http://example.com')
+            expect(data).toEqual(['entry1', 'entry2'])
+        })
+
         it('throws an error when both fetches fail', async () => {
             // @ts-ignore
             vi.mocked(fetch).mockResolvedValueOnce(new Response(null, { status: 404 }))