Hide --num-instances from services update help (#500)

Hides the `--num-instances` flag from `render services update`

GROW-2662

Support the flag (but hide it), so that if someone does pass it in, we can redirect them to the dashboard instead of fail entirely

I backlogged GROW_2661 to implement `render services scale` at Some Point™️ in the future.

GitOrigin-RevId: 2b540451cb727e091fb8b2db256512b83e5e22ff

Author: davidharting

cmd/serviceupdate.go

@@ -91,6 +91,10 @@ Provide configuration updates with flags.`,
 
 	// Instance and scaling flags
 	cmd.Flags().Int("num-instances", 0, "Number of instances")
+	// num-instances is intentionally rejected for update (see ValidateUpdate).
+	// Keep the flag registered so we can return a helpful "use the dashboard" error
+	// instead of Cobra's generic "unknown flag", but hide it from help output.
+	_ = cmd.Flags().MarkHidden("num-instances")
 	cmd.Flags().Int("max-shutdown-delay", 0, "Max shutdown delay in seconds")
 
 	// Preview and preview generation flags

cmd/serviceupdate_test.go

@@ -113,6 +113,33 @@ func TestServiceUpdateFlagsRegistration(t *testing.T) {
 	}
 }
 
+// num-instances stays registered so the command can return a helpful
+// "use the dashboard" error rather than Cobra's generic "unknown flag", but it
+// must be hidden from help output since it is never a valid update.
+func TestServiceUpdateNumInstancesFlagIsHidden(t *testing.T) {
+	cmd := newServiceUpdateTestCmd()
+
+	flag := cmd.Flags().Lookup("num-instances")
+	require.NotNil(t, flag, "num-instances flag should still be registered")
+	assert.True(t, flag.Hidden, "num-instances flag should be hidden from help")
+}
+
+// End-to-end check: render the actual --help output and confirm num-instances
+// does not leak into it. --max-shutdown-delay is a sibling visible flag that
+// proves the help text rendered, so the absence assertion can't pass vacuously.
+func TestServiceUpdateHelpOutputOmitsNumInstances(t *testing.T) {
+	cmd := newServiceUpdateTestCmd()
+	var out bytes.Buffer
+	cmd.SetOut(&out)
+	cmd.SetArgs([]string{"--help"})
+
+	require.NoError(t, cmd.Execute())
+
+	help := out.String()
+	assert.Contains(t, help, "--max-shutdown-delay", "help output should have rendered visible flags")
+	assert.NotContains(t, help, "--num-instances", "num-instances should be hidden from help output")
+}
+
 func TestServiceUpdateCommandStructure(t *testing.T) {
 	cmd := newServiceUpdateTestCmd()
 

pkg/types/service/serviceupdate.go

@@ -102,6 +102,11 @@ func (s ServiceUpdateInput) ValidateUpdate() error {
 	if !s.hasUpdateFlags() {
 		return errors.New("at least one update flag must be provided")
 	}
+	if s.NumInstances != nil {
+		// GROW-2261 will add `render services scale`. Once that ships, update this
+		// message to recommend that command instead of pointing users to the dashboard.
+		return errors.New("--num-instances is not supported for update (use the dashboard to change instance count)")
+	}
 	if s.Previews != nil {
 		if _, err := ParsePreviewsGeneration(string(*s.Previews)); err != nil {
 			return err
@@ -173,9 +178,6 @@ func (s ServiceUpdateInput) ValidateForServiceType(serviceType ServiceType) erro
 		return fmt.Errorf("--%s is not supported for %s", flag, serviceType)
 	}
 
-	if s.NumInstances != nil {
-		return fmt.Errorf("--num-instances is not supported for update (use the dashboard to change instance count)")
-	}
 	if s.HealthCheckPath != nil {
 		if err := reject("health-check-path", ServiceTypeWebService); err != nil {
 			return err

pkg/types/service/serviceupdate_test.go

@@ -109,13 +109,14 @@ func TestValidateUpdate(t *testing.T) {
 		require.NoError(t, err)
 	})
 
-	t.Run("passes with service ID and num-instances flag", func(t *testing.T) {
+	t.Run("rejects num-instances before any service-type check", func(t *testing.T) {
 		svc := servicetypes.ServiceUpdateInput{
 			NumInstances:    pointers.From(3),
 			ServiceIDOrName: "my-service-id",
 		}
 		err := svc.ValidateUpdate()
-		require.NoError(t, err)
+		require.Error(t, err)
+		assert.Contains(t, err.Error(), "--num-instances is not supported for update")
 	})
 
 	t.Run("passes with service ID and maintenance-mode flag", func(t *testing.T) {
@@ -280,12 +281,6 @@ func TestValidateForServiceType(t *testing.T) {
 			serviceType: servicetypes.ServiceTypePrivateService,
 			errMsg:      "--maintenance-mode is not supported for private_service",
 		},
-		{
-			name:        "num-instances on any type",
-			input:       servicetypes.ServiceUpdateInput{NumInstances: pointers.From(3)},
-			serviceType: servicetypes.ServiceTypeWebService,
-			errMsg:      "--num-instances is not supported for update",
-		},
 		{
 			name:        "plan on static site",
 			input:       servicetypes.ServiceUpdateInput{Plan: pointers.From("pro")},