net/url: fix parsing of URLs ending in question mark

Fixes parsing regression from https://golang.org/cl/19931 which
added the URL.ForceQuery field.

Fixes #14573

Change-Id: I89575cab3f778b1bf78b2389623c866450b26943
Reviewed-on: https://go-review.googlesource.com/20116
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Andrew Gerrand <adg@golang.org>

src/net/url/url.go

@@ -461,7 +461,7 @@ func parse(rawurl string, viaRequest bool) (url *URL, err error) {
 	}
 	url.Scheme = strings.ToLower(url.Scheme)
 
-	if strings.HasSuffix(rest, "?") {
+	if strings.HasSuffix(rest, "?") && strings.Count(rest, "?") == 1 {
 		url.ForceQuery = true
 		rest = rest[:len(rest)-1]
 	} else {

src/net/url/url_test.go

@@ -83,6 +83,17 @@ var urltests = []URLTest{
 		},
 		"",
 	},
+	// query ending in question mark (Issue 14573)
+	{
+		"http://www.google.com/?foo=bar?",
+		&URL{
+			Scheme:   "http",
+			Host:     "www.google.com",
+			Path:     "/",
+			RawQuery: "foo=bar?",
+		},
+		"",
+	},
 	// query
 	{
 		"http://www.google.com/?q=go+language",
@@ -564,8 +575,8 @@ func ufmt(u *URL) string {
 			pass = p
 		}
 	}
-	return fmt.Sprintf("opaque=%q, scheme=%q, user=%#v, pass=%#v, host=%q, path=%q, rawpath=%q, rawq=%q, frag=%q",
-		u.Opaque, u.Scheme, user, pass, u.Host, u.Path, u.RawPath, u.RawQuery, u.Fragment)
+	return fmt.Sprintf("opaque=%q, scheme=%q, user=%#v, pass=%#v, host=%q, path=%q, rawpath=%q, rawq=%q, frag=%q, forcequery=%v",
+		u.Opaque, u.Scheme, user, pass, u.Host, u.Path, u.RawPath, u.RawQuery, u.Fragment, u.ForceQuery)
 }
 
 func DoTest(t *testing.T, parse func(string) (*URL, error), name string, tests []URLTest) {