Mirror superagent behaviour in call back for creating errors

src/index.js

@@ -1,3 +1,4 @@
+const http = require("http");
 /**
  * Add to the request prototype.
  */
@@ -90,13 +91,36 @@ function callback(err, res) {
       return req._retry();
     }, delay);
   }
-
   const fn = this._callback;
   this.clearTimeout();
 
+  if (!err) {
+    try {
+      if (!this._isResponseOK(res)) {
+        let message = "Unsuccessful HTTP response";
+        if (res) {
+          message = http.STATUS_CODES[res.status] || message;
+        }
+
+        err = new Error(message);
+        err.status = res ? res.status : undefined;
+      }
+    } catch (e) {
+      err = e;
+      err.status = err.status || (res ? res.status : undefined);
+    }
+  }
+  if (!err) {
+    return fn(null, res);
+  }
+
+  err.response = res;
+
   if (err) {
     if (this._maxRetries) err.retries = this._retries - 1;
-    this.emit("error", err);
+    if (err && this.listeners("error").length > 0) {
+      this.emit("error", err);
+    }
   }
 
   fn(err, res);

tests/test.js

@@ -89,7 +89,9 @@ describe("superagent-retry-delay", function () {
         .end(function (err, res) {
           res.status.should.eql(404);
           requests.should.eql(3);
-          done(err);
+          err.response.status.should.eql(404);
+          err.message.should.eql("Not Found");
+          done();
         });
     });
 
@@ -100,7 +102,9 @@ describe("superagent-retry-delay", function () {
         .end(function (err, res) {
           res.status.should.eql(404);
           requests.should.eql(3);
-          done(err);
+          err.response.status.should.eql(404);
+          err.message.should.eql("Not Found");
+          done();
         });
     });
 
@@ -428,7 +432,8 @@ describe("superagent-retry-delay", function () {
         .end(function (err, res) {
           res.text.should.eql("Misdirected Request");
           requests.should.eql(2);
-          done(err);
+          err.message.should.eql("Misdirected Request");
+          done();
         });
     });