hide top-level namespace flags from manifest and profile commands (is…

…tio#16603)

* hide top-level namespace flags from manifest and profile commands

Add hideInheritedFlags() function to hide inhereited persisent flags
from parent commands. Use this to hide the `namespace` and
`istioNamespace` flags from the manifest and profile subcommands.

* fix lint error

istioctl/cmd/root.go

@@ -113,8 +113,13 @@ debug and diagnose their Istio mesh.
 	experimentalCmd.AddCommand(describe())
 	experimentalCmd.AddCommand(addToMeshCmd())
 
-	experimentalCmd.AddCommand(mesh.ManifestCmd())
-	experimentalCmd.AddCommand(mesh.ProfileCmd())
+	manifestCmd := mesh.ManifestCmd()
+	hideInheritedFlags(manifestCmd, "namespace", "istioNamespace")
+	experimentalCmd.AddCommand(manifestCmd)
+
+	profileCmd := mesh.ProfileCmd()
+	hideInheritedFlags(profileCmd, "namespace", "istioNamespace")
+	experimentalCmd.AddCommand(profileCmd)
 
 	rootCmd.AddCommand(collateral.CobraCommand(rootCmd, &doc.GenManHeader{
 		Title:   "Istio Control",
@@ -134,6 +139,17 @@ debug and diagnose their Istio mesh.
 	return rootCmd
 }
 
+func hideInheritedFlags(orig *cobra.Command, hidden ...string) {
+	orig.SetHelpFunc(func(cmd *cobra.Command, args []string) {
+		for _, hidden := range hidden {
+			cmd.Flags().MarkHidden(hidden) // nolint: errcheck
+		}
+
+		orig.SetHelpFunc(nil)
+		orig.HelpFunc()(cmd, args)
+	})
+}
+
 func istioPersistentPreRunE(_ *cobra.Command, _ []string) error {
 	if err := log.Configure(loggingOptions); err != nil {
 		return err

istioctl/cmd/root_test.go

@@ -0,0 +1,81 @@
+// Copyright 2019 Istio Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package cmd
+
+import (
+	"bytes"
+	"strings"
+	"testing"
+
+	"github.com/spf13/cobra"
+)
+
+func checkHelpForFlag(t *testing.T, gotHelpText, flag string, wantExists bool) {
+	t.Helper()
+
+	if strings.Contains(gotHelpText, flag) != wantExists {
+		if wantExists {
+			t.Errorf("%q flag was expected but not found in help text", flag)
+		} else {
+			t.Errorf("%q flag was found in help text but not expected", flag)
+		}
+	}
+}
+
+func TestHideInheritedFlags(t *testing.T) {
+	const (
+		parentFlag0 = "parent-flag0"
+		parentFlag1 = "parent-flag1"
+		parentFlag2 = "parent-flag2"
+		childFlag2  = "child-flag2"
+	)
+	parent := &cobra.Command{Use: "parent"}
+	_ = parent.PersistentFlags().String(parentFlag0, "", parentFlag0)
+	_ = parent.PersistentFlags().String(parentFlag1, "", parentFlag1)
+	_ = parent.PersistentFlags().String(parentFlag2, "", parentFlag2)
+	var out bytes.Buffer
+	parent.SetOutput(&out)
+
+	child := &cobra.Command{
+		Use: "child",
+		Run: func(c *cobra.Command, args []string) {},
+	}
+	_ = parent.PersistentFlags().String(childFlag2, "", childFlag2)
+	parent.AddCommand(child)
+
+	// verify both parent flags and the child flag are visible by default
+	parent.SetArgs([]string{"child", "--help"})
+	if err := parent.Execute(); err != nil {
+		t.Fatal(err)
+	}
+	got := out.String()
+	out.Reset()
+	checkHelpForFlag(t, got, parentFlag0, true)
+	checkHelpForFlag(t, got, parentFlag1, true)
+	checkHelpForFlag(t, got, parentFlag2, true)
+	checkHelpForFlag(t, got, childFlag2, true)
+
+	// verify the hidden parent flag is not visible in help text
+	hideInheritedFlags(child, parentFlag1, parentFlag2)
+	if err := parent.Execute(); err != nil {
+		t.Fatal(err)
+	}
+	got = out.String()
+	out.Reset()
+	checkHelpForFlag(t, got, parentFlag0, true)
+	checkHelpForFlag(t, got, parentFlag1, false)
+	checkHelpForFlag(t, got, parentFlag1, false)
+	checkHelpForFlag(t, got, childFlag2, true)
+}