printer: don't write a newline on empty objects

This is to match the same criteria as in gofmt.

Fixes #94

Signed-off-by: Miquel Sabaté Solà <msabate@suse.com>

hcl/printer/nodes.go

@@ -221,12 +221,12 @@ func (p *printer) objectType(o *ast.ObjectType) []byte {
 	defer un(trace(p, "ObjectType"))
 	var buf bytes.Buffer
 	buf.WriteString("{")
-	buf.WriteByte(newline)
 
 	var index int
 	var nextItem token.Pos
-	var commented bool
+	var commented, newlinePrinted bool
 	for {
+
 		// Print stand alone comments
 		for _, c := range p.standaloneComments {
 			for _, comment := range c.List {
@@ -238,6 +238,13 @@ func (p *printer) objectType(o *ast.ObjectType) []byte {
 				}
 
 				if comment.Pos().After(p.prev) && comment.Pos().Before(nextItem) {
+					// If there are standalone comments and the initial newline has not
+					// been printed yet, do it now.
+					if !newlinePrinted {
+						newlinePrinted = true
+						buf.WriteByte(newline)
+					}
+
 					// add newline if it's between other printed nodes
 					if index > 0 {
 						commented = true
@@ -258,6 +265,14 @@ func (p *printer) objectType(o *ast.ObjectType) []byte {
 			break
 		}
 
+		// At this point we are sure that it's not a totally empty block: print
+		// the initial newline if it hasn't been printed yet by the previous
+		// block about standalone comments.
+		if !newlinePrinted {
+			buf.WriteByte(newline)
+			newlinePrinted = true
+		}
+
 		// check if we have adjacent one liner items. If yes we'll going to align
 		// the comments.
 		var aligned []*ast.ObjectItem

hcl/printer/printer_test.go

@@ -29,6 +29,7 @@ var data = []entry{
 	{"comment.input", "comment.golden"},
 	{"comment_aligned.input", "comment_aligned.golden"},
 	{"comment_standalone.input", "comment_standalone.golden"},
+	{"empty_block.input", "empty_block.golden"},
 }
 
 func TestFiles(t *testing.T) {

hcl/printer/testdata/empty_block.golden

@@ -0,0 +1,13 @@
+variable "foo" {}
+
+variable "foo" {}
+
+variable "foo" {
+	# Standalone comment should be still here
+}
+
+foo {}
+
+foo {
+	bar = "mssola"
+}

hcl/printer/testdata/empty_block.input

@@ -0,0 +1,14 @@
+variable "foo" {}
+variable "foo" {
+}
+
+variable "foo" {
+	# Standalone comment should be still here
+}
+
+foo {
+}
+
+foo {
+  bar = "mssola"
+}