feat: add fetch parameter to fetchWithCache (#482)

* feat: add `fetch` parameter to `fetchWithCache`

* chore: update test

Author: eduardoboucas

packages/cache/src/fetchwithcache.test.ts

@@ -307,4 +307,24 @@ describe('`fetchWithCache`', () => {
     mockFetch.restore()
     expect(mockFetch.fulfilled).toBe(true)
   })
+
+  test('Accepts a custom `fetch` implementation', async () => {
+    const mockFetch = new MockFetch()
+      .get({
+        url: 'https://example.netlify/.netlify/cache/https%3A%2F%2Fnetlify.com%2F',
+        response: new Response(null, { status: 404 }),
+      })
+      .post({
+        url: 'https://example.netlify/.netlify/cache/https%3A%2F%2Fnetlify.com%2F',
+        response: new Response(null, { status: 201 }),
+      })
+      .inject()
+    const customFetch: typeof globalThis.fetch = async () => new Response('rijwiel')
+
+    const response = await fetchWithCache('https://netlify.com', { fetch: customFetch })
+    expect(await response.text()).toBe('rijwiel')
+
+    mockFetch.restore()
+    expect(mockFetch.fulfilled).toBe(true)
+  })
 })

packages/cache/src/fetchwithcache.ts

@@ -31,6 +31,11 @@ type CacheOptions = CacheSettings & {
    */
   cache?: NetlifyCache | string
 
+  /**
+   * A custom `fetch` implementation to be used instead of the native one.
+   */
+  fetch?: typeof globalThis.fetch
+
   /**
    * When `fetchWithCache` fetches a new response and adds it to the cache, the
    * `Promise` it returns waits for both the network call to finish and for the
@@ -115,6 +120,8 @@ export const fetchWithCache: FetchWithCache = async (
     return cached
   }
 
+  const { fetch = globalThis.fetch } = cacheOptions
+
   const fresh = await fetch(request)
   if (!fresh.body) {
     return fresh