enforce required flags (#502)

command.go

@@ -693,6 +693,9 @@ func (c *Command) execute(a []string) (err error) {
 		c.PreRun(c, argWoFlags)
 	}
 
+	if err := c.validateRequiredFlags(); err != nil {
+		return err
+	}
 	if c.RunE != nil {
 		if err := c.RunE(c, argWoFlags); err != nil {
 			return err
@@ -810,6 +813,25 @@ func (c *Command) ValidateArgs(args []string) error {
 	return c.Args(c, args)
 }
 
+func (c *Command) validateRequiredFlags() error {
+	flags := c.Flags()
+	missingFlagNames := []string{}
+	flags.VisitAll(func(pflag *flag.Flag) {
+		requiredAnnotation, found := pflag.Annotations[BashCompOneRequiredFlag]
+		if !found {
+			return
+		}
+		if (requiredAnnotation[0] == "true") && !pflag.Changed {
+			missingFlagNames = append(missingFlagNames, pflag.Name)
+		}
+	})
+
+	if len(missingFlagNames) > 0 {
+		return fmt.Errorf(`Required flag(s) "%s" have/has not been set`, strings.Join(missingFlagNames, `", "`))
+	}
+	return nil
+}
+
 // InitDefaultHelpFlag adds default help flag to c.
 // It is called automatically by executing the c or by calling help and usage.
 // If c already has help flag, it will do nothing.

command_test.go

@@ -438,3 +438,51 @@ func TestTraverseWithBadChildFlag(t *testing.T) {
 		t.Fatalf("wrong command %q expected %q", c.Name(), sub.Name())
 	}
 }
+
+func TestRequiredFlags(t *testing.T) {
+	c := &Command{Use: "c", Run: func(*Command, []string) {}}
+	output := new(bytes.Buffer)
+	c.SetOutput(output)
+	c.Flags().String("foo1", "", "required foo1")
+	c.MarkFlagRequired("foo1")
+	c.Flags().String("foo2", "", "required foo2")
+	c.MarkFlagRequired("foo2")
+	c.Flags().String("bar", "", "optional bar")
+
+	expected := fmt.Sprintf("Required flag(s) %q, %q have/has not been set", "foo1", "foo2")
+
+	if err := c.Execute(); err != nil {
+		if err.Error() != expected {
+			t.Errorf("expected %v, got %v", expected, err.Error())
+		}
+	}
+}
+
+func TestPersistentRequiredFlags(t *testing.T) {
+	parent := &Command{Use: "parent", Run: func(*Command, []string) {}}
+	output := new(bytes.Buffer)
+	parent.SetOutput(output)
+	parent.PersistentFlags().String("foo1", "", "required foo1")
+	parent.MarkPersistentFlagRequired("foo1")
+	parent.PersistentFlags().String("foo2", "", "required foo2")
+	parent.MarkPersistentFlagRequired("foo2")
+	parent.Flags().String("foo3", "", "optional foo3")
+
+	child := &Command{Use: "child", Run: func(*Command, []string) {}}
+	child.Flags().String("bar1", "", "required bar1")
+	child.MarkFlagRequired("bar1")
+	child.Flags().String("bar2", "", "required bar2")
+	child.MarkFlagRequired("bar2")
+	child.Flags().String("bar3", "", "optional bar3")
+
+	parent.AddCommand(child)
+	parent.SetArgs([]string{"child"})
+
+	expected := fmt.Sprintf("Required flag(s) %q, %q, %q, %q have/has not been set", "bar1", "bar2", "foo1", "foo2")
+
+	if err := parent.Execute(); err != nil {
+		if err.Error() != expected {
+			t.Errorf("expected %v, got %v", expected, err.Error())
+		}
+	}
+}