[PATCH v2] Include .response property on Errors as documented (#1039)

When fetch fails as the result of a server error, callers may want to
examine the headers and/or content of the response to determine the
nature of the error.  Provide this information in the .response property
on the rejection Error object as currently documented in the HTTP Client
section of README.md.

Changes in v2:
- Apply responseInterceptor to error responses
- Add tests to cover responseInterceptor behavior on error responses

Signed-off-by: Kevin Locke <[email protected]>

Author: kevinoid

src/http.js

@@ -37,17 +37,29 @@ export default function http(url, request = {}) {
   }
 
   return fetch(request.url, request).then((res) => {
-    if (!res.ok) {
-      const error = new Error(res.statusText)
-      error.statusCode = error.status = res.status
-      throw error
-    }
-    return self.serializeRes(res, url, request).then((_res) => {
+    const serialized = self.serializeRes(res, url, request).then((_res) => {
       if (request.responseInterceptor) {
         _res = request.responseInterceptor(_res) || _res
       }
       return _res
     })
+
+    if (!res.ok) {
+      const error = new Error(res.statusText)
+      error.statusCode = error.status = res.status
+      return serialized.then(
+        (_res) => {
+          error.response = _res
+          throw error
+        },
+        (resError) => {
+          error.responseError = resError
+          throw error
+        }
+      )
+    }
+
+    return serialized
   })
 }
 

test/http.js

@@ -38,6 +38,67 @@ describe('http', () => {
     })
   })
 
+  it('should include status code and response with HTTP Error', () => {
+    xapp = xmock()
+    xapp.get('http://swagger.io', (req, res) => res.status(400).send('hi'))
+
+    return http({
+      url: 'http://swagger.io'
+    })
+    .then(
+      (res) => {
+        throw new Error('Expected rejection for HTTP status 400')
+      },
+      (err) => {
+        expect(err.status).toEqual(400)
+        expect(err.statusCode).toEqual(400)
+        expect(err.response.text).toEqual('hi')
+      }
+    )
+  })
+
+  it('should apply responseInterceptor to error responses', () => {
+    xapp = xmock()
+    xapp.get('http://swagger.io', (req, res) => res.status(400).send('hi'))
+
+    return http({
+      url: 'http://swagger.io',
+      responseInterceptor: (res) => {
+        res.testValue = 5
+      }
+    })
+    .then(
+      (res) => {
+        throw new Error('Expected rejection for HTTP status 400')
+      },
+      (err) => {
+        expect(err.response.testValue).toEqual(5)
+      }
+    )
+  })
+
+  it('should set responseError on responseInterceptor Error', () => {
+    xapp = xmock()
+    xapp.get('http://swagger.io', (req, res) => res.status(400).send('hi'))
+
+    const testError = new Error()
+    return http({
+      url: 'http://swagger.io',
+      responseInterceptor: (res) => {
+        throw testError
+      }
+    })
+    .then(
+      (res) => {
+        throw new Error('Expected rejection for HTTP status 400')
+      },
+      (err) => {
+        expect(err.response).toEqual(null)
+        expect(err.responseError).toBe(testError)
+      }
+    )
+  })
+
   describe('serializeHeaders', function () {
     it('should handle FetchAPI Headers object, which is iterable', function () {
       // Given