codegen: fix client init for interceptor-only services (#3906)

* codegen: make union collection traversal deterministic

Sort object attributes before collecting union types in service and HTTP codegen so NameScope-assigned union identifiers do not oscillate across runs. Add regression tests that assert union naming remains stable when object field declaration order is reversed.

* codegen: fix client init for no-method services

When a service has a client interceptor but no methods, client codegen emitted an
unnamed goa.Endpoint parameter. Generate a zero-endpoint NewClient signature and
add a regression test.

Author: raphael

codegen/service/client_test.go

@@ -33,6 +33,7 @@ func TestClient(t *testing.T) {
 		{"client-bidirectional-streaming", testdata.BidirectionalStreamingMethodDSL, testdata.BidirectionalStreamingMethodClient},
 		{"client-bidirectional-streaming-no-payload", testdata.BidirectionalStreamingNoPayloadMethodDSL, testdata.BidirectionalStreamingNoPayloadMethodClient},
 		{"client-interceptor", testdata.EndpointWithClientInterceptorDSL, testdata.InterceptorClient},
+		{"client-interceptor-no-method", testdata.NoMethodClientInterceptorDSL, testdata.NoMethodInterceptorClient},
 	}
 	for _, c := range cases {
 		t.Run(c.Name, func(t *testing.T) {

codegen/service/templates/service_client_init.go.tpl

@@ -1,5 +1,5 @@
 {{ printf "New%s initializes a %q service client given the endpoints." .ClientVarName .Name | comment }}
-func New{{ .ClientVarName }}({{ .ClientInitArgs }} goa.Endpoint{{ if .HasClientInterceptors }}, ci ClientInterceptors{{ end }}) *{{ .ClientVarName }} {
+func New{{ .ClientVarName }}({{ if .ClientInitArgs }}{{ .ClientInitArgs }} goa.Endpoint{{ if .HasClientInterceptors }}, ci ClientInterceptors{{ end }}{{ else }}{{ if .HasClientInterceptors }}ci ClientInterceptors{{ end }}{{ end }}) *{{ .ClientVarName }} {
     return &{{ .ClientVarName }}{
     {{- range .Methods }}
         {{ .EndpointField }}: {{ if .ClientInterceptors }}Wrap{{ .VarName }}ClientEndpoint({{ end }}{{ .ArgName }}{{ if .ClientInterceptors }}, ci){{ end }},

codegen/service/testdata/client_code.go

@@ -346,3 +346,14 @@ func (c *Client) Method(ctx context.Context, p string) (res string, err error) {
 	return ires.(string), nil
 }
 `
+
+const NoMethodInterceptorClient = `// Client is the "NoMethodClientInterceptor" service client.
+type Client struct {
+}
+
+// NewClient initializes a "NoMethodClientInterceptor" service client given the
+// endpoints.
+func NewClient(ci ClientInterceptors) *Client {
+	return &Client{}
+}
+`

codegen/service/testdata/service_dsls.go

@@ -1041,6 +1041,13 @@ var EndpointWithClientInterceptorDSL = func() {
 	})
 }
 
+var NoMethodClientInterceptorDSL = func() {
+	Interceptor("tracing")
+	Service("NoMethodClientInterceptor", func() {
+		ClientInterceptor("tracing")
+	})
+}
+
 var MultipleAPIKeySecurityDSL = func() {
 	var APIKeyAuth = APIKeySecurity("api_key")
 	var TenantKeyAuth = APIKeySecurity("tenant")