#164 Addressing gzip error on Content-Length zero (#165)

* don't use gzipped reader when response content-length is zero
* add test case for auto gzip response
         1. gzipped empty response, content-length will not be empty, because of gzip header
         2. no gzipped body and content-length is zero

client.go

@@ -801,7 +801,7 @@ func (c *Client) execute(req *Request) (*Response, error) {
 		body := resp.Body
 
 		// GitHub #142
-		if strings.EqualFold(resp.Header.Get(hdrContentEncodingKey), "gzip") {
+		if strings.EqualFold(resp.Header.Get(hdrContentEncodingKey), "gzip") && resp.ContentLength > 0 {
 			if _, ok := body.(*gzip.Reader); !ok {
 				body, err = gzip.NewReader(body)
 				if err != nil {

client_test.go

@@ -479,16 +479,22 @@ func TestAutoGzip(t *testing.T) {
 	defer ts.Close()
 
 	c := New()
+	testcases := []struct{ url, want string }{
+		{ts.URL + "/gzip-test", "This is Gzip response testing"},
+		{ts.URL + "/gzip-test-gziped-empty-body", ""},
+		{ts.URL + "/gzip-test-no-gziped-body", ""},
+	}
+	for _, tc := range testcases {
+		resp, err := c.R().
+			SetHeader("Accept-Encoding", "gzip").
+			Get(tc.url)
 
-	resp, err := c.R().
-		SetHeader("Accept-Encoding", "gzip").
-		Get(ts.URL + "/gzip-test")
-
-	assertError(t, err)
-	assertEqual(t, http.StatusOK, resp.StatusCode())
-	assertEqual(t, "200 OK", resp.Status())
-	assertNotNil(t, resp.Body())
-	assertEqual(t, "This is Gzip response testing", resp.String())
+		assertError(t, err)
+		assertEqual(t, http.StatusOK, resp.StatusCode())
+		assertEqual(t, "200 OK", resp.Status())
+		assertNotNil(t, resp.Body())
+		assertEqual(t, tc.want, resp.String())
 
-	logResponse(t, resp)
+		logResponse(t, resp)
+	}
 }

resty_test.go

@@ -450,7 +450,19 @@ func createGenServer(t *testing.T) *httptest.Server {
 				zw := gzip.NewWriter(w)
 				zw.Write([]byte("This is Gzip response testing"))
 				zw.Close()
+			} else if r.URL.Path == "/gzip-test-gziped-empty-body" {
+				w.Header().Set(hdrContentTypeKey, plainTextType)
+				w.Header().Set(hdrContentEncodingKey, "gzip")
+				zw := gzip.NewWriter(w)
+				// write gziped empty body
+				zw.Write([]byte(""))
+				zw.Close()
+			} else if r.URL.Path == "/gzip-test-no-gziped-body" {
+				w.Header().Set(hdrContentTypeKey, plainTextType)
+				w.Header().Set(hdrContentEncodingKey, "gzip")
+				// don't write body
 			}
+
 			return
 		}