Merge pull request #1975 from dearchap/dont_check_req_flags

Dont check required flags until command action is executed

Author: dearchap

command.go

@@ -554,12 +554,6 @@ func (cmd *Command) Run(ctx context.Context, osArgs []string) (deferErr error) {
 		}()
 	}
 
-	if err := cmd.checkRequiredFlags(); err != nil {
-		cmd.isInError = true
-		_ = ShowSubcommandHelp(cmd)
-		return err
-	}
-
 	for _, grp := range cmd.MutuallyExclusiveFlags {
 		if err := grp.check(cmd); err != nil {
 			_ = ShowSubcommandHelp(cmd)
@@ -636,6 +630,12 @@ func (cmd *Command) Run(ctx context.Context, osArgs []string) (deferErr error) {
 	if cmd.Action == nil {
 		cmd.Action = helpCommandAction
 	} else {
+		if err := cmd.checkAllRequiredFlags(); err != nil {
+			cmd.isInError = true
+			_ = ShowSubcommandHelp(cmd)
+			return err
+		}
+
 		if err := cmd.checkPersistentRequiredFlags(); err != nil {
 			cmd.isInError = true
 			_ = ShowSubcommandHelp(cmd)
@@ -993,6 +993,15 @@ func (cmd *Command) checkRequiredFlag(f Flag) (bool, string) {
 	return true, ""
 }
 
+func (cmd *Command) checkAllRequiredFlags() requiredFlagsErr {
+	if cmd.parent != nil {
+		if err := cmd.parent.checkRequiredFlags(); err != nil {
+			return err
+		}
+	}
+	return cmd.checkRequiredFlags()
+}
+
 func (cmd *Command) checkRequiredFlags() requiredFlagsErr {
 	tracef("checking for required flags (cmd=%[1]q)", cmd.Name)
 

command_test.go

@@ -2941,6 +2941,76 @@ func TestPersistentFlagIsSet(t *testing.T) {
 	require.True(t, resultIsSet)
 }
 
+func TestRequiredFlagDelayed(t *testing.T) {
+	sf := &StringFlag{
+		Name:     "result",
+		Required: true,
+	}
+
+	expectedErr := &errRequiredFlags{
+		missingFlags: []string{sf.Name},
+	}
+
+	tests := []struct {
+		name        string
+		args        []string
+		errExpected error
+	}{
+		{
+			name:        "leaf help",
+			args:        []string{"root", "sub", "-h"},
+			errExpected: nil,
+		},
+		{
+			name:        "leaf action",
+			args:        []string{"root", "sub"},
+			errExpected: expectedErr,
+		},
+		{
+			name:        "leaf flags set",
+			args:        []string{"root", "sub", "--if", "10"},
+			errExpected: expectedErr,
+		},
+		{
+			name:        "leaf invalid flags set",
+			args:        []string{"root", "sub", "--xx"},
+			errExpected: expectedErr,
+		},
+	}
+
+	app := &Command{
+		Name: "root",
+		Flags: []Flag{
+			sf,
+		},
+		Commands: []*Command{
+			{
+				Name: "sub",
+				Flags: []Flag{
+					&IntFlag{
+						Name:     "if",
+						Required: true,
+					},
+				},
+				Action: func(ctx context.Context, c *Command) error {
+					return nil
+				},
+			},
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			err := app.Run(context.Background(), test.args)
+			if test.errExpected == nil {
+				require.NoError(t, err)
+			} else {
+				require.ErrorAs(t, err, &test.errExpected)
+			}
+		})
+	}
+}
+
 func TestRequiredPersistentFlag(t *testing.T) {
 	app := &Command{
 		Name: "root",