- decoded structs may now use the ast.Node type to save the raw ast.Node; conceptually similar to how json.RawMessage works and is useful in situations where you would like to either (a) defer decoding or (b) require additional meta-data like #Pos

.gitignore

@@ -1 +1,7 @@
 y.output
+
+# ignore intellij files
+.idea
+*.iml
+*.ipr
+*.iws

decoder.go

@@ -15,6 +15,11 @@ import (
 // This is the tag to use with structures to have settings for HCL
 const tagName = "hcl"
 
+var (
+	// nodeType holds a reference to the type of ast.Node
+	nodeType reflect.Type = findNodeType()
+)
+
 // Decode reads the given input and decodes it into the structure
 // given by `out`.
 func Decode(out interface{}, in string) error {
@@ -158,6 +163,14 @@ func (d *decoder) decodeInt(name string, node ast.Node, result reflect.Value) er
 }
 
 func (d *decoder) decodeInterface(name string, node ast.Node, result reflect.Value) error {
+	// When we see an ast.Node, we retain the value to enable deferred decoding.
+	// Very useful in situations where we want to preserve ast.Node information
+	// like Pos
+	if result.Type() == nodeType && result.CanSet() {
+		result.Set(reflect.ValueOf(node))
+		return nil
+	}
+
 	var set reflect.Value
 	redecode := true
 
@@ -574,3 +587,12 @@ func (d *decoder) decodeStruct(name string, node ast.Node, result reflect.Value)
 
 	return nil
 }
+
+// findNodeType returns the type of ast.Node
+func findNodeType() reflect.Type {
+	var nodeContainer struct {
+		Node ast.Node
+	}
+	value := reflect.ValueOf(nodeContainer).FieldByName("Node")
+	return value.Type()
+}

decoder_test.go

@@ -5,6 +5,8 @@ import (
 	"path/filepath"
 	"reflect"
 	"testing"
+
+	"github.com/hashicorp/hcl/hcl/ast"
 )
 
 func TestDecode_interface(t *testing.T) {
@@ -586,3 +588,77 @@ func TestDecode_intString(t *testing.T) {
 		t.Fatalf("bad: %#v", value.Count)
 	}
 }
+
+func TestDecode_Node(t *testing.T) {
+	// given
+	var value struct {
+		Content ast.Node
+		Nested  struct {
+			Content ast.Node
+		}
+	}
+
+	content := `
+content {
+	hello = "world"
+}
+`
+
+	// when
+	err := Decode(&value, content)
+
+	// then
+	if err != nil {
+		t.Errorf("unable to decode content, %v", err)
+		return
+	}
+
+	// verify ast.Node can be decoded later
+	var v map[string]interface{}
+	err = DecodeObject(&v, value.Content)
+	if err != nil {
+		t.Errorf("unable to decode content, %v", err)
+		return
+	}
+
+	if v["hello"] != "world" {
+		t.Errorf("expected mapping to be returned")
+	}
+}
+
+func TestDecode_NestedNode(t *testing.T) {
+	// given
+	var value struct {
+		Nested  struct {
+			Content ast.Node
+		}
+	}
+
+	content := `
+nested "content" {
+	hello = "world"
+}
+`
+
+	// when
+	err := Decode(&value, content)
+
+	// then
+	if err != nil {
+		t.Errorf("unable to decode content, %v", err)
+		return
+	}
+
+	// verify ast.Node can be decoded later
+	var v map[string]interface{}
+	err = DecodeObject(&v, value.Nested.Content)
+	if err != nil {
+		t.Errorf("unable to decode content, %v", err)
+		return
+	}
+
+	if v["hello"] != "world" {
+		t.Errorf("expected mapping to be returned")
+	}
+}
+