DisableFlagParsing must disable flag completion (#1161)

When a command has set DisableFlagParsing=true, it means Cobra should
not be handling flags for that command but should let the command
handle them itself.  In fact, Cobra normally won't have been told at all
about flags for this command.

Not knowing about the flags of the command also implies that Cobra
cannot perform flag completion as it does not have the necessary info.

This commit still tries to do flag name completion, but when
DisableFlagParsing==true, it continues on so that ValidArgsFunction will
be called; this allows the program to handle completion for its own
flags when DisableFlagParsing==true.

Signed-off-by: Marc Khouzam <marc.khouzam@montreal.ca>

completions_test.go

@@ -2543,3 +2543,64 @@ func TestMultipleShorthandFlagCompletion(t *testing.T) {
 		t.Errorf("expected: %q, got: %q", expected, output)
 	}
 }
+
+func TestCompleteWithDisableFlagParsing(t *testing.T) {
+
+	flagValidArgs := func(cmd *Command, args []string, toComplete string) ([]string, ShellCompDirective) {
+		return []string{"--flag", "-f"}, ShellCompDirectiveNoFileComp
+	}
+
+	rootCmd := &Command{Use: "root", Args: NoArgs, Run: emptyRun}
+	childCmd := &Command{
+		Use:                "child",
+		Run:                emptyRun,
+		DisableFlagParsing: true,
+		ValidArgsFunction:  flagValidArgs,
+	}
+	rootCmd.AddCommand(childCmd)
+
+	rootCmd.PersistentFlags().StringP("persistent", "p", "", "persistent flag")
+	childCmd.Flags().StringP("nonPersistent", "n", "", "non-persistent flag")
+
+	// Test that when DisableFlagParsing==true, ValidArgsFunction is called to complete flag names,
+	// after Cobra tried to complete the flags it knows about.
+	childCmd.DisableFlagParsing = true
+	output, err := executeCommand(rootCmd, ShellCompNoDescRequestCmd, "child", "-")
+	if err != nil {
+		t.Errorf("Unexpected error: %v", err)
+	}
+
+	expected := strings.Join([]string{
+		"--persistent",
+		"-p",
+		"--nonPersistent",
+		"-n",
+		"--flag",
+		"-f",
+		":4",
+		"Completion ended with directive: ShellCompDirectiveNoFileComp", ""}, "\n")
+
+	if output != expected {
+		t.Errorf("expected: %q, got: %q", expected, output)
+	}
+
+	// Test that when DisableFlagParsing==false, Cobra completes the flags itself and ValidArgsFunction is not called
+	childCmd.DisableFlagParsing = false
+	output, err = executeCommand(rootCmd, ShellCompNoDescRequestCmd, "child", "-")
+	if err != nil {
+		t.Errorf("Unexpected error: %v", err)
+	}
+
+	// Cobra was not told of any flags, so it returns nothing
+	expected = strings.Join([]string{
+		"--persistent",
+		"-p",
+		"--nonPersistent",
+		"-n",
+		":4",
+		"Completion ended with directive: ShellCompDirectiveNoFileComp", ""}, "\n")
+
+	if output != expected {
+		t.Errorf("expected: %q, got: %q", expected, output)
+	}
+}