perf: use errors.New when possible (#1490)

Related: googleapis/google-cloud-go#9749

internal/gengapic/generator.go

@@ -312,7 +312,7 @@ func (g *generator) nestedName(nested pbinfo.ProtoType) string {
 // * The field is not annotated with google.api.field_behavior = REQUIRED.
 // * The field name is listed in google.api.publishing.method_settings.auto_populated_fields.
 // * The field is annotated with google.api.field_info.format = UUID4.
-func (g *generator) autoPopulatedFields(servName string, m *descriptor.MethodDescriptorProto) []*descriptor.FieldDescriptorProto {
+func (g *generator) autoPopulatedFields(_ string, m *descriptor.MethodDescriptorProto) []*descriptor.FieldDescriptorProto {
 	var apfs []string
 	// Find the service config's AutoPopulatedFields entry by method name.
 	mfqn := g.fqn(m)

internal/gengapic/genrest.go

@@ -706,7 +706,7 @@ func (g *generator) serverStreamRESTCall(servName string, s *descriptor.ServiceD
 	p("")
 	p("func (c *%s) CloseSend() error {", streamClient)
 	p("  // This is a no-op to fulfill the interface.")
-	p(`  return fmt.Errorf("this method is not implemented for a server-stream")`)
+	p(`  return errors.New("this method is not implemented for a server-stream")`)
 	p("}")
 	p("")
 	p("func (c *%s) Context() context.Context {", streamClient)
@@ -715,17 +715,17 @@ func (g *generator) serverStreamRESTCall(servName string, s *descriptor.ServiceD
 	p("")
 	p("func (c *%s) SendMsg(m interface{}) error {", streamClient)
 	p("  // This is a no-op to fulfill the interface.")
-	p(`  return fmt.Errorf("this method is not implemented for a server-stream")`)
+	p(`  return errors.New("this method is not implemented for a server-stream")`)
 	p("}")
 	p("")
 	p("func (c *%s) RecvMsg(m interface{}) error {", streamClient)
 	p("  // This is a no-op to fulfill the interface.")
-	p(`  return fmt.Errorf("this method is not implemented, use Recv")`)
+	p(`  return errors.New("this method is not implemented, use Recv")`)
 	p("}")
 	p("")
 
 	g.imports[pbinfo.ImportSpec{Path: "context"}] = true
-	g.imports[pbinfo.ImportSpec{Path: "fmt"}] = true
+	g.imports[pbinfo.ImportSpec{Path: "errors"}] = true
 	g.imports[pbinfo.ImportSpec{Path: "google.golang.org/grpc/metadata"}] = true
 
 	return nil
@@ -748,12 +748,12 @@ func (g *generator) noRequestStreamRESTCall(servName string, s *descriptor.Servi
 
 	p("func (c *%s) %s(ctx context.Context, opts ...gax.CallOption) (%s.%s_%sClient, error) {",
 		lowcaseServName, m.GetName(), servSpec.Name, s.GetName(), m.GetName())
-	p(`  return nil, fmt.Errorf("%s not yet supported for REST clients")`, m.GetName())
+	p(`  return nil, errors.New("%s not yet supported for REST clients")`, m.GetName())
 	p("}")
 	p("")
 
 	g.imports[pbinfo.ImportSpec{Path: "context"}] = true
-	g.imports[pbinfo.ImportSpec{Path: "fmt"}] = true
+	g.imports[pbinfo.ImportSpec{Path: "errors"}] = true
 
 	return nil
 }
@@ -775,9 +775,6 @@ func (g *generator) pagingRESTCall(servName string, m *descriptor.MethodDescript
 		return err
 	}
 	info := getHTTPInfo(m)
-	if err != nil {
-		return err
-	}
 	if info == nil {
 		return fmt.Errorf("method has no http info: %q", m.GetName())
 	}

internal/gengapic/genrest_test.go

@@ -819,6 +819,7 @@ func TestGenRestMethod(t *testing.T) {
 			imports: map[pbinfo.ImportSpec]bool{
 				{Path: "bytes"}:   true,
 				{Path: "context"}: true,
+				{Path: "errors"}:  true,
 				{Path: "fmt"}:     true,
 				{Path: "google.golang.org/api/googleapi"}:                        true,
 				{Path: "net/url"}:                                                true,
@@ -835,7 +836,7 @@ func TestGenRestMethod(t *testing.T) {
 			options: &options{},
 			imports: map[pbinfo.ImportSpec]bool{
 				{Path: "context"}: true,
-				{Path: "fmt"}:     true,
+				{Path: "errors"}:  true,
 				{Name: "foopb", Path: "google.golang.org/genproto/cloud/foo/v1"}: true,
 			},
 		},

internal/gengapic/mixins_test.go

@@ -283,7 +283,7 @@ func TestGetOperationPathOverride(t *testing.T) {
 			want: "/v2/%s",
 			http: &annotations.Http{
 				Rules: []*annotations.HttpRule{
-					&annotations.HttpRule{
+					{
 						Selector: "google.longrunning.Operations.GetOperation",
 						Pattern: &annotations.HttpRule_Get{
 							Get: "/v2/{operation=projects/*/locations/*/operations/*}",

internal/gengapic/testdata/rest_ClientStreamRPC.want

@@ -1,4 +1,4 @@
 func (c *fooRESTClient) ClientStreamRPC(ctx context.Context, opts ...gax.CallOption) (foopb.FooService_ClientStreamRPCClient, error) {
-	return nil, fmt.Errorf("ClientStreamRPC not yet supported for REST clients")
+	return nil, errors.New("ClientStreamRPC not yet supported for REST clients")
 }
 

internal/gengapic/testdata/rest_ServerStreamRPC.want

@@ -90,7 +90,7 @@ func (c *serverStreamRPCRESTClient) Trailer() metadata.MD {
 
 func (c *serverStreamRPCRESTClient) CloseSend() error {
 	// This is a no-op to fulfill the interface.
-	return fmt.Errorf("this method is not implemented for a server-stream")
+	return errors.New("this method is not implemented for a server-stream")
 }
 
 func (c *serverStreamRPCRESTClient) Context() context.Context {
@@ -99,11 +99,11 @@ func (c *serverStreamRPCRESTClient) Context() context.Context {
 
 func (c *serverStreamRPCRESTClient) SendMsg(m interface{}) error {
 	// This is a no-op to fulfill the interface.
-	return fmt.Errorf("this method is not implemented for a server-stream")
+	return errors.New("this method is not implemented for a server-stream")
 }
 
 func (c *serverStreamRPCRESTClient) RecvMsg(m interface{}) error {
 	// This is a no-op to fulfill the interface.
-	return fmt.Errorf("this method is not implemented, use Recv")
+	return errors.New("this method is not implemented, use Recv")
 }