Call Run(...) for all parent nodes.

Instead of just the leaf command. Fixes #30.

README.md

@@ -166,6 +166,10 @@ A more robust approach is to break each command out into their own structs:
 3. Call `kong.Kong.Parse()` to obtain a `kong.Context`.
 4. Call `kong.Context.Run(bindings...)` to call the selected parsed command.
 
+Once a command node is selected by Kong it will search from that node back to the root. Each
+encountered command node with a `Run(...) error` will be called in reverse order. This allows
+sub-trees to be re-used fairly conveniently.
+
 In addition to values bound with the `kong.Bind(...)` option, any values
 passed through to `kong.Context.Run(...)` are also bindable to the target's
 `Run()` arguments.

context.go

@@ -88,6 +88,10 @@ func (c *Context) Bind(args ...interface{}) {
 }
 
 // BindTo adds a binding to the Context.
+//
+// This will typically have to be called like so:
+//
+//    BindTo(impl, (*MyInterface)(nil))
 func (c *Context) BindTo(impl, iface interface{}) {
 	c.bindings[reflect.TypeOf(iface).Elem()] = reflect.ValueOf(impl)
 }
@@ -493,16 +497,32 @@ func (c *Context) Run(bindings ...interface{}) (err error) {
 	if node == nil {
 		return fmt.Errorf("no command selected")
 	}
-	method := getMethod(node.Target, "Run")
-	if !method.IsValid() {
-		return fmt.Errorf("no Run() method on %s", node.Target)
+	type targetMethod struct {
+		node   *Node
+		method reflect.Value
+	}
+	methods := []targetMethod{}
+	for i := 0; node != nil; i, node = i+1, node.Parent {
+		method := getMethod(node.Target, "Run")
+		if method.IsValid() {
+			methods = append(methods, targetMethod{node, method})
+		}
+	}
+	if len(methods) == 0 {
+		return fmt.Errorf("no Run() method found in hierarchy of %s", c.Selected().Summary())
 	}
 	_, err = c.Apply()
 	if err != nil {
 		return err
 	}
-	binds := c.Kong.bindings.clone().add(bindings...).add(c).merge(c.bindings)
-	return callMethod("Run", node.Target, method, binds)
+
+	for _, method := range methods {
+		binds := c.Kong.bindings.clone().add(bindings...).add(c).merge(c.bindings)
+		if err = callMethod("Run", method.node.Target, method.method, binds); err != nil {
+			return err
+		}
+	}
+	return nil
 }
 
 // PrintUsage to Kong's stdout.

kong_test.go

@@ -513,9 +513,22 @@ func (c *cmdWithRun) Run(key string) error {
 	return nil
 }
 
+type parentCmdWithRun struct {
+	Flag       string
+	SubCommand struct {
+		Arg string `arg:""`
+	} `cmd:""`
+}
+
+func (p *parentCmdWithRun) Run(key string) error {
+	p.SubCommand.Arg += key
+	return nil
+}
+
 type grammarWithRun struct {
-	One cmdWithRun `cmd:""`
-	Two cmdWithRun `cmd:""`
+	One   cmdWithRun       `cmd:""`
+	Two   cmdWithRun       `cmd:""`
+	Three parentCmdWithRun `cmd:""`
 }
 
 func TestRun(t *testing.T) {
@@ -532,6 +545,12 @@ func TestRun(t *testing.T) {
 	require.NoError(t, err)
 	err = ctx.Run("ERROR")
 	require.Error(t, err)
+
+	ctx, err = p.Parse([]string{"three", "sub-command", "arg"})
+	require.NoError(t, err)
+	err = ctx.Run("ping")
+	require.NoError(t, err)
+	require.Equal(t, "argping", cli.Three.SubCommand.Arg)
 }
 
 func TestInterpolationIntoModel(t *testing.T) {