hcl/printer: print lead comments for lists properly

hcl/printer/nodes.go

@@ -62,6 +62,14 @@ func (p *printer) collectComments(node ast.Node) {
 	ast.Walk(node, func(nn ast.Node) (ast.Node, bool) {
 		switch t := nn.(type) {
 		case *ast.LiteralType:
+			if t.LeadComment != nil {
+				for _, comment := range t.LeadComment.List {
+					if _, ok := standaloneComments[comment.Pos()]; ok {
+						delete(standaloneComments, comment.Pos())
+					}
+				}
+			}
+
 			if t.LineComment != nil {
 				for _, comment := range t.LineComment.List {
 					if _, ok := standaloneComments[comment.Pos()]; ok {
@@ -445,6 +453,17 @@ func (p *printer) list(l *ast.ListType) []byte {
 			// multiline list, add newline before we add each item
 			buf.WriteByte(newline)
 			insertSpaceBeforeItem = false
+
+			// If we have a lead comment, then we want to write that first
+			leadComment := false
+			if lit, ok := item.(*ast.LiteralType); ok && lit.LeadComment != nil {
+				leadComment = true
+				for _, comment := range lit.LeadComment.List {
+					buf.Write(p.indent([]byte(comment.Text)))
+					buf.WriteByte(newline)
+				}
+			}
+
 			// also indent each line
 			val := p.output(item)
 			curLen := len(val)
@@ -466,6 +485,10 @@ func (p *printer) list(l *ast.ListType) []byte {
 			if i == len(l.List)-1 {
 				buf.WriteByte(newline)
 			}
+
+			if leadComment {
+				buf.WriteByte(newline)
+			}
 		} else {
 			if insertSpaceBeforeItem {
 				buf.WriteByte(blank)

hcl/printer/printer_test.go

@@ -33,6 +33,7 @@ var data = []entry{
 	{"list.input", "list.golden"},
 	{"comment.input", "comment.golden"},
 	{"comment_aligned.input", "comment_aligned.golden"},
+	{"comment_array.input", "comment_array.golden"},
 	{"comment_newline.input", "comment_newline.golden"},
 	{"comment_standalone.input", "comment_standalone.golden"},
 	{"empty_block.input", "empty_block.golden"},

hcl/printer/testdata/comment_array.golden

@@ -0,0 +1,10 @@
+banana = [
+  # I really want to comment this item in the array.
+  "a",
+
+  # This as well
+  "b",
+
+  "c", # And C
+  "d",
+]

hcl/printer/testdata/comment_array.input

@@ -0,0 +1,10 @@
+banana = [
+  # I really want to comment this item in the array.
+  "a",
+
+  # This as well
+  "b",
+
+  "c", # And C
+  "d",
+]