Add tests showing that relative paths are handled properly.

PiperOrigin-RevId: 242949234

transformer/internal/amphtml/urls.go

@@ -53,7 +53,7 @@ func isProtocolRelative(urlParam string) bool {
 
 // ToAbsoluteURL absolute-ifies |urlParam|, using |baseURL| as the base if
 // |urlParam| is relative. If |urlParam| contains a fragment, this method
-// will return only a fragment if it's absolute URL matches |documentURL|,
+// will return only a fragment if its absolute URL matches |documentURL|,
 // which prevents changing an in-document navigation to a out-of-document
 // navigation.
 func ToAbsoluteURL(documentURL string, baseURL *url.URL,

transformer/internal/amphtml/urls_test.go

@@ -185,6 +185,13 @@ func TestToAbsoluteURL(t *testing.T) {
 			documentURL: rootURL,
 			expected:    "https://foo.com?q",
 		},
+		{
+			desc:        "relative",
+			input:       "../blah.jpg",
+			baseURL:     fooURL + "/",
+			documentURL: rootURL,
+			expected:    "https://www.example.com/blah.jpg",
+		},
 	}
 	for _, tc := range tcs {
 		baseURL, _ := url.Parse(tc.baseURL)
@@ -274,6 +281,12 @@ func TestGetCacheURL(t *testing.T) {
 			expectedImage: "https://www-example-com.cdn.ampproject.org/i/s/www.example.com/cdn.ampproject.org/blah.jpg",
 			expectedOther: "https://www-example-com.cdn.ampproject.org/r/s/www.example.com/cdn.ampproject.org/blah.jpg",
 		},
+		{
+			desc:          "absolute with relative path",
+			input:         "https://www.example.com/cdn.ampproject.org/one/two/three/../../../blah.jpg",
+			expectedImage: "https://www-example-com.cdn.ampproject.org/i/s/www.example.com/cdn.ampproject.org/blah.jpg",
+			expectedOther: "https://www-example-com.cdn.ampproject.org/r/s/www.example.com/cdn.ampproject.org/blah.jpg",
+		},
 	}
 	base, _ := url.Parse("https://example.com/")
 	for _, tc := range tcs {