hcl/printer: preserve list comment on first line

hcl/printer/nodes.go

@@ -579,7 +579,10 @@ func (p *printer) list(l *ast.ListType) []byte {
 			}
 
 			// Output the item itself
-			buf.Write(p.output(item))
+			// also indent each line
+			val := p.output(item)
+			curLen := len(val)
+			buf.Write(val)
 
 			// If this is a heredoc item we always have to output a newline
 			// so that it parses properly.
@@ -592,6 +595,18 @@ func (p *printer) list(l *ast.ListType) []byte {
 				buf.WriteString(",")
 				insertSpaceBeforeItem = true
 			}
+
+			if lit, ok := item.(*ast.LiteralType); ok && lit.LineComment != nil {
+				// if the next item doesn't have any comments, do not align
+				buf.WriteByte(blank) // align one space
+				for i := 0; i < longestLine-curLen; i++ {
+					buf.WriteByte(blank)
+				}
+
+				for _, comment := range lit.LineComment.List {
+					buf.WriteString(comment.Text)
+				}
+			}
 		}
 
 	}

hcl/printer/printer_test.go

@@ -31,6 +31,7 @@ type entry struct {
 var data = []entry{
 	{"complexhcl.input", "complexhcl.golden"},
 	{"list.input", "list.golden"},
+	{"list_comment.input", "list_comment.golden"},
 	{"comment.input", "comment.golden"},
 	{"comment_aligned.input", "comment_aligned.golden"},
 	{"comment_array.input", "comment_array.golden"},

hcl/printer/testdata/list_comment.golden

@@ -0,0 +1,7 @@
+foo = [1, # Hello
+  2,
+]
+
+foo = [1, # Hello
+  2, # World
+]

hcl/printer/testdata/list_comment.input

@@ -0,0 +1,6 @@
+foo = [1, # Hello
+2]
+
+foo = [1, # Hello
+2, # World
+]