gateway: test Accept header overides conflicting ?format

gateway/gateway_test.go

@@ -440,7 +440,7 @@ func TestHeaders(t *testing.T) {
 			DeserializedResponses: true,
 		})
 
-		runTest := func(name, path, accept, host, expectedContentPath string) {
+		runTest := func(name, path, accept, host, expectedContentLocationHdr string) {
 			t.Run(name, func(t *testing.T) {
 				t.Parallel()
 
@@ -461,7 +461,7 @@ func TestHeaders(t *testing.T) {
 				require.NoError(t, err)
 
 				require.Equal(t, http.StatusOK, resp.StatusCode, string(body))
-				require.Equal(t, expectedContentPath, resp.Header.Get("Content-Location"))
+				require.Equal(t, expectedContentLocationHdr, resp.Header.Get("Content-Location"))
 			})
 		}
 
@@ -490,6 +490,8 @@ func TestHeaders(t *testing.T) {
 			runTest("DNSLink gateway with Accept: "+responseFormat, "/empty-dir/", responseFormat, dnslinkGatewayHost, "/empty-dir/?format="+formatParam)
 			runTest("DNSLink gateway with ?format="+formatParam, "/empty-dir/?format="+formatParam, "", dnslinkGatewayHost, "")
 		}
+
+		runTest("Accept: application/vnd.ipld.car overrides ?format=raw in Content-Location", contentPath+"?format=raw", "application/vnd.ipld.car", "", contentPath+"?format=car")
 	})
 }
 

gateway/handler.go

@@ -652,13 +652,22 @@ func customResponseFormat(r *http.Request) (mediaType string, params map[string]
 // correct caching of such format requests when the format is passed via the
 // Accept header, for example.
 func addContentLocation(r *http.Request, w http.ResponseWriter, rq *requestData) {
-	// Skip Content-Location if no explicit format was requested via the HTTP
-	// Accept header, or if it was requested via URL query parameter.
-	if rq.responseFormat == "" || r.URL.Query().Get("format") != "" {
+	// Skip Content-Location if no explicit format was requested
+	// via Accept HTTP header or ?format URL param
+	if rq.responseFormat == "" {
 		return
 	}
 
 	format := responseFormatToFormatParam[rq.responseFormat]
+
+	// Skip Content-Location if there is no conflict between
+	// 'format' in URL and value in 'Accept' header.
+	// If both are present and don't match, we continue and generate
+	// Content-Location to ensure value from Accept overrides 'format' from URL.
+	if urlFormat := r.URL.Query().Get("format"); urlFormat != "" && urlFormat == format {
+		return
+	}
+
 	path := r.URL.Path
 	if p, ok := r.Context().Value(OriginalPathKey).(string); ok {
 		path = p