fix: http error handling regression (#1285)

* tests: add failing test case provided in ticket
* fix: throw original fetch error if we don't have any response data

Author: shockey

src/http.js

@@ -46,6 +46,11 @@ export default async function http(url, request = {}) {
     }
   }
   catch (resError) {
+    if (!res) {
+      // res is completely absent, so we can't construct our own error
+      // so we'll just throw the error we got
+      throw resError
+    }
     const error = new Error(res.statusText)
     error.statusCode = error.status = res.status
     error.responseError = resError

test/client.js

@@ -171,6 +171,20 @@ describe('http', () => {
       })
   })
 
+  /**
+   * See https://github.com/swagger-api/swagger-js/issues/1277
+   */
+  it('should return a helpful error when the connection is refused', () => {
+    return Swagger('http://localhost:1/untouchable.yaml')
+      .then((client) => {
+        throw new Error('Expected an error.')
+      })
+      .catch((error) => {
+        expect(error.message).toEqual('request to http://localhost:1/untouchable.yaml failed, reason: connect ECONNREFUSED 127.0.0.1:1')
+        expect(error.name).toEqual('FetchError')
+      })
+  })
+
   /**
    * See https://github.com/swagger-api/swagger-js/issues/1002
    */