terraform: ResourceConfig.Get gets interpolated if possible

terraform/context.go

@@ -75,9 +75,11 @@ func NewContext(opts *ContextOpts) *Context {
 
 	// Calculate all the default variables
 	defaultVars := make(map[string]string)
-	for _, v := range opts.Config.Variables {
-		for k, val := range v.DefaultsMap() {
-			defaultVars[k] = val
+	if opts.Config != nil {
+		for _, v := range opts.Config.Variables {
+			for k, val := range v.DefaultsMap() {
+				defaultVars[k] = val
+			}
 		}
 	}
 

terraform/resource.go

@@ -89,9 +89,43 @@ func (c *ResourceConfig) CheckSet(keys []string) []error {
 // The second return value is true if the get was successful. Get will
 // not succeed if the value is being computed.
 func (c *ResourceConfig) Get(k string) (interface{}, bool) {
+	result, ok := c.get(k, c.Config)
+	if ok {
+		return result, ok
+	}
+
+	return c.get(k, c.Raw)
+}
+
+// IsSet checks if the key in the configuration is set. A key is set if
+// it has a value or the value is being computed (is unknown currently).
+//
+// This function should be used rather than checking the keys of the
+// raw configuration itself, since a key may be omitted from the raw
+// configuration if it is being computed.
+func (c *ResourceConfig) IsSet(k string) bool {
+	if c == nil {
+		return false
+	}
+
+	for _, ck := range c.ComputedKeys {
+		if ck == k {
+			return true
+		}
+	}
+
+	if _, ok := c.Get(k); ok {
+		return true
+	}
+
+	return false
+}
+
+func (c *ResourceConfig) get(
+	k string, raw map[string]interface{}) (interface{}, bool) {
 	parts := strings.Split(k, ".")
 
-	var current interface{} = c.Raw
+	var current interface{} = raw
 	for _, part := range parts {
 		if current == nil {
 			return nil, false
@@ -123,30 +157,6 @@ func (c *ResourceConfig) Get(k string) (interface{}, bool) {
 	return current, true
 }
 
-// IsSet checks if the key in the configuration is set. A key is set if
-// it has a value or the value is being computed (is unknown currently).
-//
-// This function should be used rather than checking the keys of the
-// raw configuration itself, since a key may be omitted from the raw
-// configuration if it is being computed.
-func (c *ResourceConfig) IsSet(k string) bool {
-	if c == nil {
-		return false
-	}
-
-	for _, ck := range c.ComputedKeys {
-		if ck == k {
-			return true
-		}
-	}
-
-	if _, ok := c.Get(k); ok {
-		return true
-	}
-
-	return false
-}
-
 func (c *ResourceConfig) interpolate(ctx *Context) error {
 	if c == nil {
 		return nil

terraform/resource_test.go

@@ -3,6 +3,8 @@ package terraform
 import (
 	"reflect"
 	"testing"
+
+	"github.com/hashicorp/terraform/config"
 )
 
 func TestResource_Vars(t *testing.T) {
@@ -29,3 +31,49 @@ func TestResource_Vars(t *testing.T) {
 		t.Fatalf("bad: %#v", actual)
 	}
 }
+
+func TestResourceConfigGet(t *testing.T) {
+	cases := []struct {
+		Config map[string]interface{}
+		Vars   map[string]string
+		Key    string
+		Value  interface{}
+	}{
+		{
+			Config: map[string]interface{}{
+				"foo": "${var.foo}",
+			},
+			Key:   "foo",
+			Value: "${var.foo}",
+		},
+
+		{
+			Config: map[string]interface{}{
+				"foo": "${var.foo}",
+			},
+			Vars:  map[string]string{"foo": "bar"},
+			Key:   "foo",
+			Value: "bar",
+		},
+	}
+
+	for i, tc := range cases {
+		rawC, err := config.NewRawConfig(tc.Config)
+		if err != nil {
+			t.Fatalf("err: %s", err)
+		}
+		rc := NewResourceConfig(rawC)
+
+		if tc.Vars != nil {
+			ctx := NewContext(&ContextOpts{Variables: tc.Vars})
+			if err := rc.interpolate(ctx); err != nil {
+				t.Fatalf("err: %s", err)
+			}
+		}
+
+		v, _ := rc.Get(tc.Key)
+		if !reflect.DeepEqual(v, tc.Value) {
+			t.Fatalf("%d bad: %#v", i, v)
+		}
+	}
+}