Improve service config errors handling

clientconn.go

@@ -860,9 +860,10 @@ func (ac *addrConn) tryUpdateAddrs(addrs []resolver.Address) bool {
 // GetMethodConfig gets the method config of the input method.
 // If there's an exact match for input method (i.e. /service/method), we return
 // the corresponding MethodConfig.
-// If there isn't an exact match for the input method, we look for the default config
-// under the service (i.e /service/). If there is a default MethodConfig for
-// the service, we return it.
+// If there isn't an exact match for the input method, we look for the service's default
+// config under the service (i.e /service/) and then for the default for all services (empty string).
+//
+// If there is a default MethodConfig for the service, we return it.
 // Otherwise, we return an empty MethodConfig.
 func (cc *ClientConn) GetMethodConfig(method string) MethodConfig {
 	// TODO: Avoid the locking here.

service_config.go

@@ -230,16 +230,20 @@ type jsonName struct {
 	Method  *string
 }
 
-var errIgnoreName = errors.New("ignore name")
+var (
+	errMissingService             = errors.New("'service' is missing")
+	errDuplicatedName             = errors.New("duplicated name")
+	errEmptyServiceNonEmptyMethod = errors.New("cannot combine empty 'service' and non-empty 'method'")
+)
 
 func (j jsonName) generatePath() (string, error) {
 	if j.Service == nil {
-		return "", errIgnoreName
+		return "", errMissingService
 	}
 	if *j.Service == "" {
 		// when 'service' is empty 'method' must be empty as well
 		if j.Method != nil && *j.Method != "" {
-			return "", errors.New("cannot combine empty 'service' and non-empty 'method'")
+			return "", errEmptyServiceNonEmptyMethod
 		}
 		return "", nil
 	}
@@ -336,15 +340,12 @@ func parseServiceConfig(js string) *serviceconfig.ParseResult {
 		for i, n := range *m.Name {
 			path, err := n.generatePath()
 			if err != nil {
-				if err == errIgnoreName {
-					continue
-				}
 				grpclog.Warningf("grpc: parseServiceConfig error unmarshaling %s due to methodConfig[%d]: %v", js, i, err)
 				return &serviceconfig.ParseResult{Err: err}
 			}
 
 			if _, ok := paths[path]; ok {
-				err = errors.New("duplicated name")
+				err = errDuplicatedName
 				grpclog.Warningf("grpc: parseServiceConfig error unmarshaling %s due to methodConfig[%d]: %v", js, i, err)
 				return &serviceconfig.ParseResult{Err: err}
 			}

service_config_test.go

@@ -373,6 +373,22 @@ func (s) TestParseMsgSize(t *testing.T) {
 	runParseTests(t, testcases)
 }
 
+func (s) TestParseMethodConfigNullService(t *testing.T) {
+	runParseTests(t, []parseTestCase{{
+		`{
+  "methodConfig": [{
+    "name": [
+      {
+        "service": null,
+        "method": "Bar"
+      }
+    ],
+    "waitForReady": true
+  }]
+}`, nil, true,
+	}})
+}
+
 func (s) TestParseMethodConfigEmptyServiceAndNonEmptyMethod(t *testing.T) {
 	runParseTests(t, []parseTestCase{{
 		`{