fix: BatchGet rule now singularizes correctly. (#585)

rules/aip0231/response_resource_field.go

@@ -16,6 +16,7 @@ package aip0231
 
 import (
 	"fmt"
+	"strings"
 
 	"github.com/gertd/go-pluralize"
 	"github.com/googleapis/api-linter/lint"
@@ -27,11 +28,9 @@ var resourceField = &lint.MessageRule{
 	Name:   lint.NewRuleName(231, "response-resource-field"),
 	OnlyIf: isBatchGetResponseMessage,
 	LintMessage: func(m *desc.MessageDescriptor) []lint.Problem {
-		// the singular form the resource name, the first letter is Capitalized.
-		// Note: Use m.GetName()[8 : len(m.GetName())-9] to retrieve the resource
-		// name from the the batch get response, for example:
-		// "BatchGetBooksResponse" -> "Books"
-		resourceMsgName := pluralize.NewClient().Singular(m.GetName()[8 : len(m.GetName())-9])
+		// The singular form the resource message name; the first letter capitalized.
+		plural := strings.TrimSuffix(strings.TrimPrefix(m.GetName(), "BatchGet"), "Response")
+		resourceMsgName := pluralize.NewClient().Singular(plural)
 
 		for _, fieldDesc := range m.GetFields() {
 			if msgDesc := fieldDesc.GetMessageType(); msgDesc != nil && msgDesc.GetName() == resourceMsgName {

rules/aip0231/response_resource_field_test.go

@@ -32,27 +32,35 @@ func TestResourceField(t *testing.T) {
 		{
 			testName: "Valid",
 			src: `
-message BatchGetBooksResponse {
-  // Books requested.
-  repeated Book books = 1;
-}`,
+				message BatchGetBooksResponse {
+					// Books requested.
+					repeated Book books = 1;
+				}`,
+			problems: testutils.Problems{},
+		},
+		{
+			testName: "ValidEs",
+			src: `
+				message BatchGetMatchesResponse {
+					repeated Match matches = 1;
+				}`,
 			problems: testutils.Problems{},
 		},
 		{
 			testName: "FieldIsNotRepeated",
 			src: `
-message BatchGetBooksResponse {
-  // Book requested.
-  Book book = 1;
-}`,
+				message BatchGetBooksResponse {
+					// Book requested.
+					Book book = 1;
+				}`,
 			problems: testutils.Problems{{Message: "The \"Book\" type field on Batch Get Response message should be repeated"}},
 		},
 		{
 			testName: "MissingField",
 			src: `
-message BatchGetBooksResponse {
-  string response = 1;
-}`,
+				message BatchGetBooksResponse {
+					string response = 1;
+				}`,
 			problems: testutils.Problems{{Message: "Message \"BatchGetBooksResponse\" has no \"Book\" type field"}},
 			problemDesc: func(m *desc.MessageDescriptor) desc.Descriptor {
 				return m
@@ -64,9 +72,10 @@ message BatchGetBooksResponse {
 	for _, test := range tests {
 		t.Run(test.testName, func(t *testing.T) {
 			template := `
-{{.Src}}
-message Book {
-}`
+				{{.Src}}
+				message Book {}
+				message Match {}
+			`
 			file := testutils.ParseProto3Tmpl(t, template, struct{ Src string }{test.src})
 
 			m := file.GetMessageTypes()[0]