app: Allocate Metadata map automatically

app.go

@@ -160,6 +160,10 @@ func (a *App) Setup() {
 		a.categories = a.categories.AddCommand(command.Category, command)
 	}
 	sort.Sort(a.categories)
+
+	if a.Metadata == nil {
+		a.Metadata = make(map[string]interface{})
+	}
 }
 
 // Run is the entry point to the cli app. Parses the arguments slice and routes

command_test.go

@@ -73,6 +73,54 @@ func TestCommand_Run_DoesNotOverwriteErrorFromBefore(t *testing.T) {
 	}
 }
 
+func TestCommand_Run_BeforeSavesMetadata(t *testing.T) {
+	var receivedMsgFromAction string
+	var receivedMsgFromAfter string
+
+	app := NewApp()
+	app.Commands = []Command{
+		{
+			Name: "bar",
+			Before: func(c *Context) error {
+				c.App.Metadata["msg"] = "hello world"
+				return nil
+			},
+			Action: func(c *Context) error {
+				msg, ok := c.App.Metadata["msg"]
+				if !ok {
+					return errors.New("msg not found")
+				}
+				receivedMsgFromAction = msg.(string)
+				return nil
+			},
+			After: func(c *Context) error {
+				msg, ok := c.App.Metadata["msg"]
+				if !ok {
+					return errors.New("msg not found")
+				}
+				receivedMsgFromAfter = msg.(string)
+				return nil
+			},
+		},
+	}
+
+	err := app.Run([]string{"foo", "bar"})
+	if err != nil {
+		t.Fatalf("expected no error from Run, got %s", err)
+	}
+
+	expectedMsg := "hello world"
+
+	if receivedMsgFromAction != expectedMsg {
+		t.Fatalf("expected msg from Action to match. Given: %q\nExpected: %q",
+			receivedMsgFromAction, expectedMsg)
+	}
+	if receivedMsgFromAfter != expectedMsg {
+		t.Fatalf("expected msg from After to match. Given: %q\nExpected: %q",
+			receivedMsgFromAction, expectedMsg)
+	}
+}
+
 func TestCommand_OnUsageError_WithWrongFlagValue(t *testing.T) {
 	app := NewApp()
 	app.Commands = []Command{