packer/rpc: implement hook Cancel

packer/rpc/hook.go

@@ -2,6 +2,7 @@ package rpc
 
 import (
 	"github.com/mitchellh/packer/packer"
+	"log"
 	"net/rpc"
 )
 
@@ -38,7 +39,10 @@ func (h *hook) Run(name string, ui packer.Ui, comm packer.Communicator, data int
 }
 
 func (h *hook) Cancel() {
-	// TODO(mitchellh): implement
+	err := h.client.Call("Hook.Cancel", new(interface{}), new(interface{}))
+	if err != nil {
+		log.Printf("Hook.Cancel error: %s", err)
+	}
 }
 
 func (h *HookServer) Run(args *HookRunArgs, reply *interface{}) error {
@@ -54,3 +58,8 @@ func (h *HookServer) Run(args *HookRunArgs, reply *interface{}) error {
 	*reply = nil
 	return nil
 }
+
+func (h *HookServer) Cancel(args *interface{}, reply *interface{}) error {
+	h.hook.Cancel()
+	return nil
+}

packer/rpc/hook_test.go

@@ -28,6 +28,10 @@ func TestHookRPC(t *testing.T) {
 	ui := &testUi{}
 	hClient.Run("foo", ui, nil, 42)
 	assert.True(h.RunCalled, "run should be called")
+
+	// Test Cancel
+	hClient.Cancel()
+	assert.True(h.CancelCalled, "cancel should be called")
 }
 
 func TestHook_Implements(t *testing.T) {