From ccd129f7a54896ccea1fb904f125f9756be9e154 Mon Sep 17 00:00:00 2001
From: Haiyan Meng <haiyanmeng@google.com>
Date: Wed, 8 Jan 2020 10:24:00 -0800
Subject: [PATCH] Check empty http response before accessing it

---
 api/internal/crawl/crawler/github/crawler.go | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/api/internal/crawl/crawler/github/crawler.go b/api/internal/crawl/crawler/github/crawler.go
index 1696a296a..6467294da 100644
--- a/api/internal/crawl/crawler/github/crawler.go
+++ b/api/internal/crawl/crawler/github/crawler.go
@@ -118,6 +118,10 @@ func (gc githubCrawler) FetchDocument(_ context.Context, d *doc.Document) error
 		"/" + repoSpec.Ref + "/" + repoSpec.Path
 
 	handle := func(resp *http.Response, err error, path string) error {
+		if resp == nil {
+			return fmt.Errorf("empty http response (url: %s; path: %s), error: %v",
+				url, path, err)
+		}
 		if err == nil && resp.StatusCode == http.StatusOK {
 			d.IsSame = httpclient.FromCache(resp.Header)
 			defer resp.Body.Close()
@@ -577,7 +581,7 @@ func (gcl GhClient) Do(query string) (*http.Response, error) {
 	// gcl.client.Do: a non-2xx status code doesn't cause an error.
 	// See https://golang.org/pkg/net/http/#Client.Do for more info.
 	resp, err :=  gcl.client.Do(req)
-	if resp.StatusCode != http.StatusOK {
+	if resp != nil && resp.StatusCode != http.StatusOK {
 		err = fmt.Errorf("GhClient.Do(%s) failed with response code: %d",
 			query, resp.StatusCode)
 	}
@@ -591,7 +595,7 @@ func (gcl GhClient) getWithRetry(
 
 	retryCount := gcl.retryCount
 
-	for resp.StatusCode == http.StatusForbidden && retryCount > 0 {
+	for resp != nil && resp.StatusCode == http.StatusForbidden && retryCount > 0 {
 		retryTime := resp.Header.Get("Retry-After")
 		i, errAtoi := strconv.Atoi(retryTime)
 		if errAtoi != nil {