packer: Add SetDebug to Build objects

packer/build.go

@@ -21,6 +21,12 @@ type Build interface {
 	// Cancel will cancel a running build. This will block until the build
 	// is actually completely cancelled.
 	Cancel()
+
+	// SetDebug will enable/disable debug mode. Debug mode is always
+	// enabled by adding the additional key "packer_debug" to boolean
+	// true in the configuration of the various components. This must
+	// be called prior to Prepare.
+	SetDebug(bool)
 }
 
 // A build struct represents a single build job, the result of which should
@@ -34,6 +40,7 @@ type coreBuild struct {
 	hooks         map[string][]Hook
 	provisioners  []coreBuildProvisioner
 
+	debug         bool
 	prepareCalled bool
 }
 
@@ -103,6 +110,14 @@ func (b *coreBuild) Run(ui Ui, cache Cache) (Artifact, error) {
 	return b.builder.Run(ui, hook, cache)
 }
 
+func (b *coreBuild) SetDebug(val bool) {
+	if b.prepareCalled {
+		panic("prepare has already been called")
+	}
+
+	b.debug = val
+}
+
 // Cancels the build if it is running.
 func (b *coreBuild) Cancel() {
 	b.builder.Cancel()

packer/rpc/build.go

@@ -58,6 +58,12 @@ func (b *build) Run(ui packer.Ui, cache packer.Cache) (packer.Artifact, error) {
 	return Artifact(client), nil
 }
 
+func (b *build) SetDebug(val bool) {
+	if err := b.client.Call("Build.SetDebug", val, new(interface{})); err != nil {
+		panic(err)
+	}
+}
+
 func (b *build) Cancel() {
 	if err := b.client.Call("Build.Cancel", new(interface{}), new(interface{})); err != nil {
 		panic(err)
@@ -93,6 +99,11 @@ func (b *BuildServer) Run(args *BuildRunArgs, reply *string) error {
 	return nil
 }
 
+func (b *BuildServer) SetDebug(val *bool, reply *interface{}) error {
+	b.build.SetDebug(*val)
+	return nil
+}
+
 func (b *BuildServer) Cancel(args *interface{}, reply *interface{}) error {
 	b.build.Cancel()
 	return nil

packer/rpc/build_test.go

@@ -16,6 +16,7 @@ type testBuild struct {
 	runCalled      bool
 	runCache       packer.Cache
 	runUi          packer.Ui
+	setDebugCalled bool
 	cancelCalled   bool
 
 	errRunResult bool
@@ -43,6 +44,10 @@ func (b *testBuild) Run(ui packer.Ui, cache packer.Cache) (packer.Artifact, erro
 	}
 }
 
+func (b *testBuild) SetDebug(bool) {
+	b.setDebugCalled = true
+}
+
 func (b *testBuild) Cancel() {
 	b.cancelCalled = true
 }
@@ -93,6 +98,10 @@ func TestBuildRPC(t *testing.T) {
 	_, err = bClient.Run(ui, cache)
 	assert.NotNil(err, "should not nil")
 
+	// Test SetDebug
+	bClient.SetDebug(true)
+	assert.True(b.setDebugCalled, "should be called")
+
 	// Test Cancel
 	bClient.Cancel()
 	assert.True(b.cancelCalled, "cancel should be called")