hclwrite: Support for creating new blocks and clearing bodies

hclwrite/ast_block.go

@@ -23,6 +23,13 @@ func newBlock() *Block {
 	}
 }
 
+// NewBlock constructs a new, empty block with the given type name and labels.
+func NewBlock(typeName string, labels []string) *Block {
+	block := newBlock()
+	block.init(typeName, labels)
+	return block
+}
+
 func (b *Block) init(typeName string, labels []string) {
 	nameTok := newIdentToken(typeName)
 	nameObj := newIdentifier(nameTok)

hclwrite/ast_body.go

@@ -32,6 +32,11 @@ func (b *Body) appendItemNode(nn *node) *node {
 	return nn
 }
 
+// Clear removes all of the items from the body, making it empty.
+func (b *Body) Clear() {
+	b.children.Clear()
+}
+
 func (b *Body) AppendUnstructuredTokens(ts Tokens) {
 	b.inTree.children.Append(ts)
 }
@@ -85,6 +90,13 @@ func (b *Body) SetAttributeTraversal(name string, traversal hcl.Traversal) *Attr
 	panic("Body.SetAttributeTraversal not yet implemented")
 }
 
+// AppendBlock appends an existing block (which must not be already attached
+// to a body) to the end of the receiving body.
+func (b *Body) AppendBlock(block *Block) *Block {
+	b.appendItem(block)
+	return block
+}
+
 // AppendNewBlock appends a new nested block to the end of the receiving body
 // with the given type name and labels.
 func (b *Body) AppendNewBlock(typeName string, labels []string) *Block {

hclwrite/node.go

@@ -104,6 +104,11 @@ func (ns *nodes) BuildTokens(to Tokens) Tokens {
 	return to
 }
 
+func (ns *nodes) Clear() {
+	ns.first = nil
+	ns.last = nil
+}
+
 func (ns *nodes) Append(c nodeContent) *node {
 	n := &node{
 		content: c,