🐛[RUMF-293][fetch] handle fetch response text error (#252)

When consuming a fetch response body, it can be disturbed or locked, a rejected promise is then returned (cf https://fetch.spec.whatwg.org/#concept-body-consume-body). This rejected promise was displayed on the browser console and the corresponding request was not collected. Handle the rejected promise and add the corresponding error to the collected request response.
DataDog · Feb 6, 2020 · ce037b8 · ce037b8
1 parent 5037108
commit ce037b8
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Showing 3 changed files with 32 additions and 2 deletions.
diff --git a/packages/core/src/requestCollection.ts b/packages/core/src/requestCollection.ts
@@ -103,7 +103,12 @@ export function trackFetch(observable: RequestObservable) {
           type: RequestType.FETCH,
         })
       } else if ('status' in response) {
-        const text = await response.clone().text()
+        let text: string
+        try {
+          text = await response.clone().text()
+        } catch (e) {
+          text = `Unable to retrieve response: ${e}`
+        }
         observable.notify({
           duration,
           method,

diff --git a/packages/core/src/specHelper.ts b/packages/core/src/specHelper.ts
@@ -55,7 +55,14 @@ export class FetchStubBuilder {
         resolve({
           ...response,
           clone: () => {
-            const cloned = { text: async () => response.responseText }
+            const cloned = {
+              text: async () => {
+                if (response.responseTextError) {
+                  throw response.responseTextError
+                }
+                return response.responseText
+              },
+            }
             return cloned as Response
           },
         }) as Promise<ResponseStub>
@@ -67,6 +74,7 @@ export class FetchStubBuilder {
 
 export interface ResponseStub extends Partial<Response> {
   responseText?: string
+  responseTextError?: Error
 }
 
 export type FetchStub = (input: RequestInfo, init?: RequestInit) => FetchStubPromise

diff --git a/packages/core/test/requestCollection.spec.ts b/packages/core/test/requestCollection.spec.ts
@@ -70,6 +70,23 @@ describe('fetch tracker', () => {
     })
   })
 
+  // https://fetch.spec.whatwg.org/#concept-body-consume-body
+  it('should track fetch with response text error', (done) => {
+    fetchStub(FAKE_URL).resolveWith({ status: 200, responseTextError: new Error('locked') })
+
+    fetchStubBuilder.whenAllComplete((requests: RequestDetails[]) => {
+      const request = requests[0]
+      expect(request.type).toEqual(RequestType.FETCH)
+      expect(request.method).toEqual('GET')
+      expect(request.url).toEqual(FAKE_URL)
+      expect(request.status).toEqual(200)
+      expect(request.response).toMatch(/Error: locked/)
+      expect(isRejected(request)).toBe(false)
+      expect(isServerError(request)).toBe(false)
+      done()
+    })
+  })
+
   it('should track opaque fetch', (done) => {
     // https://fetch.spec.whatwg.org/#concept-filtered-response-opaque
     fetchStub(FAKE_URL).resolveWith({ status: 0, type: 'opaque' })