hclwrite: Adjust token spacing automatically when writing

Although our underlying parse tree retains all of the token content, it
doesn't necessarily retain all of the spacing information under editing,
and so formatting on save ensures that we'll produce a canonical result
even if some edits have been applied that have changed the expected
alignment of objects, etc.

hclwrite/ast.go

@@ -19,8 +19,12 @@ func (f *File) Body() *Body {
 }
 
 // WriteTo writes the tokens underlying the receiving file to the given writer.
+//
+// The tokens first have a simple formatting pass applied that adjusts only
+// the spaces between them.
 func (f *File) WriteTo(wr io.Writer) (int, error) {
 	tokens := f.inTree.children.BuildTokens(nil)
+	format(tokens)
 	return tokens.WriteTo(wr)
 }
 

hclwrite/ast_body.go

@@ -10,10 +10,6 @@ type Body struct {
 	inTree
 
 	items nodeSet
-
-	// indentLevel is the number of spaces that should appear at the start
-	// of lines added within this body.
-	indentLevel int
 }
 
 func (b *Body) appendItem(c nodeContent) *node {

hclwrite/parser.go

@@ -185,8 +185,6 @@ func parseBody(nativeBody *hclsyntax.Body, from inputTokens) (inputTokens, *node
 
 	body := &Body{
 		inTree: newInTree(),
-
-		indentLevel: 0, // TODO: deal with this
 		items:  newNodeSet(),
 	}
 

hclwrite/public.go

@@ -11,7 +11,7 @@ import (
 func NewFile() *File {
 	body := &Body{
 		inTree: newInTree(),
-		indentLevel: 0,
+		items:  newNodeSet(),
 	}
 	file := &File{
 		inTree: newInTree(),