hcl: add *ast.File with comments

ast/ast.go

@@ -10,6 +10,7 @@ type Node interface {
 	Pos() token.Pos
 }
 
+func (File) node()       {}
 func (ObjectList) node() {}
 func (ObjectKey) node()  {}
 func (ObjectItem) node() {}
@@ -20,6 +21,16 @@ func (ObjectType) node()   {}
 func (LiteralType) node()  {}
 func (ListType) node()     {}
 
+// File represents a single HCL file
+type File struct {
+	Node     Node            // usually a *ObjectList
+	Comments []*CommentGroup // list of all comments in the source
+}
+
+func (f *File) Pos() token.Pos {
+	return f.Node.Pos()
+}
+
 // ObjectList represents a list of ObjectItems. An HCL file itself is an
 // ObjectList.
 type ObjectList struct {

parser/parser.go

@@ -34,7 +34,7 @@ func newParser(src []byte) *Parser {
 }
 
 // Parse returns the fully parsed source and returns the abstract syntax tree.
-func Parse(src []byte) (ast.Node, error) {
+func Parse(src []byte) (*ast.File, error) {
 	p := newParser(src)
 	return p.Parse()
 }
@@ -42,8 +42,16 @@ func Parse(src []byte) (ast.Node, error) {
 var errEofToken = errors.New("EOF token found")
 
 // Parse returns the fully parsed source and returns the abstract syntax tree.
-func (p *Parser) Parse() (ast.Node, error) {
-	return p.objectList()
+func (p *Parser) Parse() (*ast.File, error) {
+	f := &ast.File{}
+	var err error
+	f.Node, err = p.objectList()
+	if err != nil {
+		return nil, err
+	}
+
+	f.Comments = p.comments
+	return f, nil
 }
 
 func (p *Parser) objectList() (*ast.ObjectList, error) {
@@ -64,7 +72,6 @@ func (p *Parser) objectList() (*ast.ObjectList, error) {
 
 		node.Add(n)
 	}
-
 	return node, nil
 }
 

printer/nodes.go

@@ -18,6 +18,13 @@ func (p *printer) output(n interface{}) []byte {
 	var buf bytes.Buffer
 
 	switch t := n.(type) {
+	case *ast.File:
+		// for i, group := range t.Comments {
+		// 	for _, comment := range group.List {
+		// 		fmt.Printf("[%d] comment = %+v\n", i, comment)
+		// 	}
+		// }
+		return p.output(t.Node)
 	case *ast.ObjectList:
 		for i, item := range t.Items {
 			buf.Write(p.objectItem(item))