Add Enabled func to Binding

pkg/gui/controllers/options_menu_action.go

@@ -25,6 +25,10 @@ func (self *OptionsMenuAction) Call() error {
 	appendBindings := func(bindings []*types.Binding, section *types.MenuSection) {
 		menuItems = append(menuItems,
 			lo.Map(bindings, func(binding *types.Binding, _ int) *types.MenuItem {
+				disabledReason := ""
+				if binding.GetDisabledReason != nil {
+					disabledReason = binding.GetDisabledReason()
+				}
 				return &types.MenuItem{
 					OpensMenu: binding.OpensMenu,
 					Label:     binding.Description,
@@ -33,11 +37,12 @@ func (self *OptionsMenuAction) Call() error {
 							return nil
 						}
 
-						return binding.Handler()
+						return self.c.IGuiCommon.CallKeybindingHandler(binding)
 					},
-					Key:     binding.Key,
-					Tooltip: binding.Tooltip,
-					Section: section,
+					Key:            binding.Key,
+					Tooltip:        binding.Tooltip,
+					DisabledReason: disabledReason,
+					Section:        section,
 				}
 			})...)
 	}

pkg/gui/gui_common.go

@@ -171,6 +171,10 @@ func (self *guiCommon) KeybindingsOpts() types.KeybindingsOpts {
 	return self.gui.keybindingOpts()
 }
 
+func (self *guiCommon) CallKeybindingHandler(binding *types.Binding) error {
+	return self.gui.callKeybindingHandler(binding)
+}
+
 func (self *guiCommon) IsAnyModeActive() bool {
 	return self.gui.helpers.Mode.IsAnyModeActive()
 }

pkg/gui/keybindings.go

@@ -375,7 +375,10 @@ func (gui *Gui) wrappedHandler(f func() error) func(g *gocui.Gui, v *gocui.View)
 }
 
 func (gui *Gui) SetKeybinding(binding *types.Binding) error {
-	handler := binding.Handler
+	handler := func() error {
+		return gui.callKeybindingHandler(binding)
+	}
+
 	// TODO: move all mouse-ey stuff into new mouse approach
 	if gocui.IsMouseKey(binding.Key) {
 		handler = func() error {
@@ -406,3 +409,14 @@ func (gui *Gui) SetMouseKeybinding(binding *gocui.ViewMouseBinding) error {
 
 	return gui.g.SetViewClickBinding(binding)
 }
+
+func (gui *Gui) callKeybindingHandler(binding *types.Binding) error {
+	disabledReason := ""
+	if binding.GetDisabledReason != nil {
+		disabledReason = binding.GetDisabledReason()
+	}
+	if disabledReason != "" {
+		return gui.c.ErrorMsg(disabledReason)
+	}
+	return binding.Handler()
+}

pkg/gui/types/common.go

@@ -104,6 +104,7 @@ type IGuiCommon interface {
 	State() IStateAccessor
 
 	KeybindingsOpts() KeybindingsOpts
+	CallKeybindingHandler(binding *Binding) error
 
 	// hopefully we can remove this once we've moved all our keybinding stuff out of the gui god struct.
 	GetInitialKeybindingsWithCustomCommands() ([]*Binding, []*gocui.ViewMouseBinding)

pkg/gui/types/keybindings.go

@@ -25,6 +25,13 @@ type Binding struct {
 
 	// to be displayed if the keybinding is highlighted from within a menu
 	Tooltip string
+
+	// Function to decide whether the command is enabled, and why. If this
+	// returns an empty string, it is; if it returns a non-empty string, it is
+	// disabled and we show the given text in an error message when trying to
+	// invoke it. When left nil, the command is always enabled. Note that this
+	// function must not do expensive calls.
+	GetDisabledReason func() string
 }
 
 // A guard is a decorator which checks something before executing a handler