hclwrite: Allow format to be called on fragment of tokens

hclwrite/format.go

@@ -296,8 +296,6 @@ func spaceAfterToken(subject, before, after *Token) bool {
 
 func linesForFormat(tokens Tokens) []formatLine {
  if len(tokens) == 0 {
- // should never happen, since we should always have EOF, but let's
- // not crash anyway.
  return make([]formatLine, 0)
  }
 
@@ -331,6 +329,16 @@ func linesForFormat(tokens Tokens) []formatLine {
  }
  }
 
+ // If a set of tokens doesn't end in TokenEOF (e.g. because it's a
+ // fragment of tokens from the middle of a file) then we might fall
+ // out here with a line still pending.
+ if lineStart < len(tokens) {
+ lines[li].lead = tokens[lineStart:]
+ if lines[li].lead[len(lines[li].lead)-1].Type == hclsyntax.TokenEOF {
+ lines[li].lead = lines[li].lead[:len(lines[li].lead)-1]
+ }
+ }
+
  // Now we'll pick off any trailing comments and attribute assignments
  // to shuffle off into the "comment" and "assign" cells.
  for i := range lines {