Folding not reversible

[dlucredativ]

RFC2822 and RFC5322 define folding as

wherever this standard allows for folding white space (not simply WSP characters), a CRLF may be inserted before any WSP

and unfolding as

Unfolding is accomplished by simply removing any CRLF that is immediately followed by WSP

By the above definition, it is unfold(fold(input)) = input. However, sub __fold_objless replaces the original WSP by $indent. What is its use case?

Email-Simple/lib/Email/Simple/Header.pm

Lines 428 to 445 in 041c3f7

	sub __fold_objless {
	my ($self, $line, $limit, $indent, $crlf) = @_;
	# We know it will not contain any new lines at present
	my $folded = "";
	while (length $line) {
	if ($line =~ s/^(.{0,$limit})(\s|\z)//) {
	$folded .= $1 . $crlf;
	$folded .= $indent if length $line;
	} else {
	# Basically nothing we can do. :(
	$folded .= $line . $crlf;
	last;
	}
	}
	return $folded;
	}

Consider

diff --git a/t/folding.t b/t/folding.t
index 9ef51cb..4e0d652 100644
--- a/t/folding.t
+++ b/t/folding.t
@@ -43,3 +43,3 @@ END
 
-  my $subject = 'A ' x 50; # Long enough to need to be folded
+  my $subject = "A\t" x 50; # Long enough to need to be folded
 
@@ -54,2 +54,3 @@ END
   unlike($email_1->as_string, qr/\Q$subject/, "we fold the 50-A line");
+  like($email_1->as_string =~ s/\r\n(?=[ \t])//gr, qr/\Q$subject/, "we fold the 50-A line reversibly");
 }

The additional test fails. I think the correct thing to do is along the lines of

diff --git a/lib/Email/Simple/Header.pm b/lib/Email/Simple/Header.pm
index 0709687..b7a3f38 100644
--- a/lib/Email/Simple/Header.pm
+++ b/lib/Email/Simple/Header.pm
@@ -434,4 +434,3 @@ sub __fold_objless {
     if ($line =~ s/^(.{0,$limit})(\s|\z)//) {
-      $folded .= $1 . $crlf;
-      $folded .= $indent if length $line;
+      $folded .= $1 . $crlf . $2;
     } else {