terraform: refresh hooks

terraform/context.go

@@ -26,6 +26,7 @@ type ContextOpts struct {
 // perform operations on infrastructure. This structure is built using
 // NewContext. See the documentation for that.
 type Context2 struct {
+	hooks        []Hook
 	module       *module.Tree
 	providers    map[string]ResourceProviderFactory
 	provisioners map[string]ResourceProvisionerFactory
@@ -41,6 +42,7 @@ type Context2 struct {
 // the values themselves.
 func NewContext2(opts *ContextOpts) *Context2 {
 	return &Context2{
+		hooks:        opts.Hooks,
 		module:       opts.Module,
 		providers:    opts.Providers,
 		provisioners: opts.Provisioners,

terraform/context_test.go

@@ -123,12 +123,11 @@ func TestContext2Refresh_ignoreUncreated(t *testing.T) {
 	}
 }
 
-/*
-func TestContextRefresh_hook(t *testing.T) {
+func TestContext2Refresh_hook(t *testing.T) {
 	h := new(MockHook)
 	p := testProvider("aws")
 	m := testModule(t, "refresh-basic")
-	ctx := testContext(t, &ContextOpts{
+	ctx := testContext2(t, &ContextOpts{
 		Module: m,
 		Hooks:  []Hook{h},
 		Providers: map[string]ResourceProviderFactory{
@@ -162,6 +161,7 @@ func TestContextRefresh_hook(t *testing.T) {
 	}
 }
 
+/*
 func TestContextRefresh_modules(t *testing.T) {
 	p := testProvider("aws")
 	m := testModule(t, "refresh-modules")

terraform/eval.go

@@ -27,6 +27,12 @@ type GraphNodeEvalable interface {
 	EvalTree() EvalNode
 }
 
+// EvalEarlyExitError is a special error return value that can be returned
+// by eval nodes that does an early exit.
+type EvalEarlyExitError struct{}
+
+func (EvalEarlyExitError) Error() string { return "early exit" }
+
 // Eval evaluates the given EvalNode with the given context, properly
 // evaluating all args in the correct order.
 func Eval(n EvalNode, ctx EvalContext) (interface{}, error) {

terraform/eval_context.go

@@ -11,6 +11,10 @@ type EvalContext interface {
 	// Path is the current module path.
 	Path() []string
 
+	// Hook is used to call hook methods. The callback is called for each
+	// hook and should return the hook action to take and the error.
+	Hook(func(Hook) (HookAction, error)) error
+
 	// InitProvider initializes the provider with the given name and
 	// returns the implementation of the resource provider or an error.
 	//
@@ -53,6 +57,9 @@ type EvalContext interface {
 // MockEvalContext is a mock version of EvalContext that can be used
 // for tests.
 type MockEvalContext struct {
+	HookCalled bool
+	HookError  error
+
 	InitProviderCalled   bool
 	InitProviderName     string
 	InitProviderProvider ResourceProvider
@@ -94,6 +101,11 @@ type MockEvalContext struct {
 	StateLock   *sync.RWMutex
 }
 
+func (c *MockEvalContext) Hook(fn func(Hook) (HookAction, error)) error {
+	c.HookCalled = true
+	return c.HookError
+}
+
 func (c *MockEvalContext) InitProvider(n string) (ResourceProvider, error) {
 	c.InitProviderCalled = true
 	c.InitProviderName = n

terraform/eval_context_builtin.go

@@ -14,6 +14,7 @@ import (
 type BuiltinEvalContext struct {
 	PathValue           []string
 	Interpolater        *Interpolater
+	Hooks               []Hook
 	Providers           map[string]ResourceProviderFactory
 	ProviderCache       map[string]ResourceProvider
 	ProviderConfigCache map[string]*ResourceConfig
@@ -27,6 +28,25 @@ type BuiltinEvalContext struct {
 	once sync.Once
 }
 
+func (ctx *BuiltinEvalContext) Hook(fn func(Hook) (HookAction, error)) error {
+	for _, h := range ctx.Hooks {
+		action, err := fn(h)
+		if err != nil {
+			return err
+		}
+
+		switch action {
+		case HookActionContinue:
+			continue
+		case HookActionHalt:
+			// Return an early exit error to trigger an early exit
+			return EvalEarlyExitError{}
+		}
+	}
+
+	return nil
+}
+
 func (ctx *BuiltinEvalContext) InitProvider(n string) (ResourceProvider, error) {
 	ctx.once.Do(ctx.init)
 

terraform/eval_refresh.go

@@ -27,8 +27,29 @@ func (n *EvalRefresh) Eval(
 		return nil, nil
 	}
 
-	n.Info.ModulePath = ctx.Path()
-	return provider.Refresh(n.Info, state)
+	// Call pre-refresh hook
+	err := ctx.Hook(func(h Hook) (HookAction, error) {
+		return h.PreRefresh(n.Info, state)
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	// Refresh!
+	state, err = provider.Refresh(n.Info, state)
+	if err != nil {
+		return nil, err
+	}
+
+	// Call post-refresh hook
+	err = ctx.Hook(func(h Hook) (HookAction, error) {
+		return h.PostRefresh(n.Info, state)
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	return state, nil
 }
 
 func (n *EvalRefresh) Type() EvalType {

terraform/eval_resource.go

@@ -0,0 +1,22 @@
+package terraform
+
+// EvalInstanceInfo is an EvalNode implementation that fills in the
+// InstanceInfo as much as it can.
+type EvalInstanceInfo struct {
+	Info *InstanceInfo
+}
+
+func (n *EvalInstanceInfo) Args() ([]EvalNode, []EvalType) {
+	return nil, nil
+}
+
+// TODO: test
+func (n *EvalInstanceInfo) Eval(
+	ctx EvalContext, args []interface{}) (interface{}, error) {
+	n.Info.ModulePath = ctx.Path()
+	return nil, nil
+}
+
+func (n *EvalInstanceInfo) Type() EvalType {
+	return EvalTypeNull
+}

terraform/graph_walk_context.go

@@ -36,6 +36,7 @@ func (w *ContextGraphWalker) EnterGraph(g *Graph) EvalContext {
 
 	return &BuiltinEvalContext{
 		PathValue:           g.Path,
+		Hooks:               w.Context.hooks,
 		Providers:           w.Context.providers,
 		ProviderCache:       w.providerCache,
 		ProviderConfigCache: w.providerConfigCache,

terraform/transform_resource.go

@@ -96,6 +96,10 @@ func (n *graphNodeExpandedResource) EvalTree() EvalNode {
 		})
 	}
 
+	// Build instance info
+	info := &InstanceInfo{Id: n.stateId(), Type: n.Resource.Type}
+	seq.Nodes = append(seq.Nodes, &EvalInstanceInfo{Info: info})
+
 	// Refresh the resource
 	seq.Nodes = append(seq.Nodes, &EvalOpFilter{
 		Ops: []walkOperation{walkRefresh},
@@ -104,9 +108,9 @@ func (n *graphNodeExpandedResource) EvalTree() EvalNode {
 			ResourceType: n.Resource.Type,
 			Dependencies: n.DependentOn(),
 			State: &EvalRefresh{
+				Info:     info,
 				Provider: &EvalGetProvider{Name: n.ProvidedBy()},
 				State:    &EvalReadState{Name: n.stateId()},
-				Info:     &InstanceInfo{Id: n.stateId(), Type: n.Resource.Type},
 			},
 		},
 	})