Backport Show non categorized flags with categorized on help

category.go

@@ -100,10 +100,24 @@ func newFlagCategories() FlagCategories {
 
 func newFlagCategoriesFromFlags(fs []Flag) FlagCategories {
 	fc := newFlagCategories()
+
+	var categorized bool
+
 	for _, fl := range fs {
 		if cf, ok := fl.(CategorizableFlag); ok {
-			if cf.GetCategory() != "" {
-				fc.AddFlag(cf.GetCategory(), fl)
+			if cat := cf.GetCategory(); cat != "" {
+				fc.AddFlag(cat, fl)
+				categorized = true
+			}
+		}
+	}
+
+	if categorized {
+		for _, fl := range fs {
+			if cf, ok := fl.(CategorizableFlag); ok {
+				if cf.GetCategory() == "" {
+					fc.AddFlag("", fl)
+				}
 			}
 		}
 	}

command_test.go

@@ -526,12 +526,15 @@ func TestCommand_VisibleFlagCategories(t *testing.T) {
 	}
 
 	vfc := cmd.VisibleFlagCategories()
-	require.NotEmpty(t, vfc)
-	assert.Equal(t, vfc[0].Name(), "cat1", "expected category name cat1")
+	require.Len(t, vfc, 2)
 
-	require.Len(t, vfc[0].Flags(), 1, "expected flag category to have just one flag")
+	assert.Equal(t, vfc[0].Name(), "", "expected category name to be empty")
 
-	fl := vfc[0].Flags()[0]
+	assert.Equal(t, vfc[1].Name(), "cat1", "expected category name cat1")
+
+	require.Len(t, vfc[1].Flags(), 1, "expected flag category to have just one flag")
+
+	fl := vfc[1].Flags()[0]
 	assert.Equal(t, fl.Names(), []string{"intd", "altd1", "altd2"})
 }
 

help_test.go

@@ -1482,3 +1482,62 @@ OPTIONS:
 		output.String(),
 	)
 }
+
+func TestCategorizedHelp(t *testing.T) {
+	// Reset HelpPrinter after this test.
+	defer func(old helpPrinter) {
+		HelpPrinter = old
+	}(HelpPrinter)
+
+	output := new(bytes.Buffer)
+	cmd := &Command{
+		Name:   "cli.test",
+		Writer: output,
+		Action: func(context.Context, *Command) error { return nil },
+		Flags: []Flag{
+			&StringFlag{
+				Name: "strd", // no category set
+			},
+			&IntFlag{
+				Name:     "intd",
+				Aliases:  []string{"altd1", "altd2"},
+				Category: "cat1",
+			},
+		},
+	}
+
+	HelpPrinter = func(w io.Writer, templ string, data interface{}) {
+		funcMap := map[string]interface{}{
+			"wrapAt": func() int {
+				return 30
+			},
+		}
+
+		HelpPrinterCustom(w, templ, data, funcMap)
+	}
+
+	r := require.New(t)
+	r.NoError(cmd.Run(buildTestContext(t), []string{"cli.test", "help"}))
+
+	r.Equal(`NAME:
+   cli.test - A new cli
+              application
+
+USAGE:
+   cli.test [global options] [command [command options]] [arguments...]
+
+COMMANDS:
+   help, h  Shows a list of
+            commands or help
+            for one command
+
+GLOBAL OPTIONS:
+   --help, -h    show help (default: false)
+   --strd value  
+
+   cat1
+
+   --intd value, --altd1 value, --altd2 value  (default: 0)
+
+`, output.String())
+}