checkpatch: improve email parsing

checkpatch doesn't report warnings for many common mistakes in emails.
Some of which are trailing commas and incorrect use of email comments.

At the same time several false positives are reported due to incorrect
handling of mail comments.  The most common of which is due to the
pattern:

<stable@vger.kernel.org> # X.X

Improve email parsing in checkpatch.

Some general email rules are defined:

- Multiple name comments should not be allowed.
- Comments inside address should not be allowed.
- In general comments should be enclosed within parentheses.
  Relaxation is given to comments beginning with #.
- Stable addresses should not begin with a name.
- Comments in stable addresses should begin only
  with a #.

Improvements to parsing:

- Detect and report unexpected content after email.
- Quoted names are excluded from comment parsing.
- Trailing dots, commas or quotes in email are removed during
  formatting. Correspondingly a BAD_SIGN_OFF warning
  is emitted.
- Improperly quoted email like '"name <address>"' are now
  warned about.

In addition, added fixes for all the possible rules.

Link: https://lore.kernel.org/linux-kernel-mentees/6c275d95c3033422addfc256a30e6ae3dd37941d.camel@perches.com/
Link: https://lore.kernel.org/linux-kernel-mentees/20201105200857.GC1333458@kroah.com/
Link: https://lkml.kernel.org/r/20201108100632.75340-1-dwaipayanray1@gmail.comSigned-off-by: Dwaipayan Ray <dwaipayanray1@gmail.com>
Suggested-by: Joe Perches <joe@perches.com>
Acked-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/checkpatch.pl

@@ -1159,6 +1159,7 @@ sub parse_email {
 	my ($formatted_email) = @_;
 
 	my $name = "";
+	my $quoted = "";
 	my $name_comment = "";
 	my $address = "";
 	my $comment = "";
@@ -1190,14 +1191,20 @@ sub parse_email {
 		}
 	}
 
-	$comment = trim($comment);
-	$name = trim($name);
-	$name =~ s/^\"|\"$//g;
-	if ($name =~ s/(\s*\([^\)]+\))\s*//) {
-		$name_comment = trim($1);
+	# Extract comments from names excluding quoted parts
+	# "John D. (Doe)" - Do not extract
+	if ($name =~ s/\"(.+)\"//) {
+		$quoted = $1;
+	}
+	while ($name =~ s/\s*($balanced_parens)\s*/ /) {
+		$name_comment .= trim($1);
 	}
+	$name =~ s/^[ \"]+|[ \"]+$//g;
+	$name = trim("$quoted $name");
+
 	$address = trim($address);
 	$address =~ s/^\<|\>$//g;
+	$comment = trim($comment);
 
 	if ($name =~ /[^\w \-]/i) { ##has "must quote" chars
 		$name =~ s/(?<!\\)"/\\"/g; ##escape quotes
@@ -1212,17 +1219,20 @@ sub format_email {
 
 	my $formatted_email;
 
-	$name_comment = trim($name_comment);
-	$comment = trim($comment);
-	$name = trim($name);
-	$name =~ s/^\"|\"$//g;
+	$name =~ s/^[ \"]+|[ \"]+$//g;
 	$address = trim($address);
+	$address =~ s/(?:\.|\,|\")+$//; ##trailing commas, dots or quotes
 
 	if ($name =~ /[^\w \-]/i) { ##has "must quote" chars
 		$name =~ s/(?<!\\)"/\\"/g; ##escape quotes
 		$name = "\"$name\"";
 	}
 
+	$name_comment = trim($name_comment);
+	$name_comment = " $name_comment" if ($name_comment ne "");
+	$comment = trim($comment);
+	$comment = " $comment" if ($comment ne "");
+
 	if ("$name" eq "") {
 		$formatted_email = "$address";
 	} else {
@@ -1240,15 +1250,11 @@ sub reformat_email {
 }
 
 sub same_email_addresses {
-	my ($email1, $email2, $match_comment) = @_;
+	my ($email1, $email2) = @_;
 
 	my ($email1_name, $name1_comment, $email1_address, $comment1) = parse_email($email1);
 	my ($email2_name, $name2_comment, $email2_address, $comment2) = parse_email($email2);
 
-	if ($match_comment != 1) {
-		return $email1_name eq $email2_name &&
-		       $email1_address eq $email2_address;
-	}
 	return $email1_name eq $email2_name &&
 	       $email1_address eq $email2_address &&
 	       $name1_comment eq $name2_comment &&
@@ -2711,7 +2717,7 @@ sub process {
 			$signoff++;
 			$in_commit_log = 0;
 			if ($author ne ''  && $authorsignoff != 1) {
-				if (same_email_addresses($1, $author, 1)) {
+				if (same_email_addresses($1, $author)) {
 					$authorsignoff = 1;
 				} else {
 					my $ctx = $1;
@@ -2807,9 +2813,77 @@ sub process {
 				$dequoted =~ s/" </ </;
 				# Don't force email to have quotes
 				# Allow just an angle bracketed address
-				if (!same_email_addresses($email, $suggested_email, 0)) {
+				if (!same_email_addresses($email, $suggested_email)) {
+					if (WARN("BAD_SIGN_OFF",
+						 "email address '$email' might be better as '$suggested_email'\n" . $herecurr) &&
+					    $fix) {
+						$fixed[$fixlinenr] =~ s/\Q$email\E/$suggested_email/;
+					}
+				}
+
+				# Address part shouldn't have comments
+				my $stripped_address = $email_address;
+				$stripped_address =~ s/\([^\(\)]*\)//g;
+				if ($email_address ne $stripped_address) {
+					if (WARN("BAD_SIGN_OFF",
+						 "address part of email should not have comments: '$email_address'\n" . $herecurr) &&
+					    $fix) {
+						$fixed[$fixlinenr] =~ s/\Q$email_address\E/$stripped_address/;
+					}
+				}
+
+				# Only one name comment should be allowed
+				my $comment_count = () = $name_comment =~ /\([^\)]+\)/g;
+				if ($comment_count > 1) {
 					WARN("BAD_SIGN_OFF",
-					     "email address '$email' might be better as '$suggested_email'\n" . $herecurr);
+					     "Use a single name comment in email: '$email'\n" . $herecurr);
+				}
+
+
+				# stable@vger.kernel.org or stable@kernel.org shouldn't
+				# have an email name. In addition commments should strictly
+				# begin with a #
+				if ($email =~ /^.*stable\@(?:vger\.)?kernel\.org/i) {
+					if (($comment ne "" && $comment !~ /^#.+/) ||
+					    ($email_name ne "")) {
+						my $cur_name = $email_name;
+						my $new_comment = $comment;
+						$cur_name =~ s/[a-zA-Z\s\-\"]+//g;
+
+						# Remove brackets enclosing comment text
+						# and # from start of comments to get comment text
+						$new_comment =~ s/^\((.*)\)$/$1/;
+						$new_comment =~ s/^\[(.*)\]$/$1/;
+						$new_comment =~ s/^[\s\#]+|\s+$//g;
+
+						$new_comment = trim("$new_comment $cur_name") if ($cur_name ne $new_comment);
+						$new_comment = " # $new_comment" if ($new_comment ne "");
+						my $new_email = "$email_address$new_comment";
+
+						if (WARN("BAD_STABLE_ADDRESS_STYLE",
+							 "Invalid email format for stable: '$email', prefer '$new_email'\n" . $herecurr) &&
+						    $fix) {
+							$fixed[$fixlinenr] =~ s/\Q$email\E/$new_email/;
+						}
+					}
+				} elsif ($comment ne "" && $comment !~ /^(?:#.+|\(.+\))$/) {
+					my $new_comment = $comment;
+
+					# Extract comment text from within brackets or
+					# c89 style /*...*/ comments
+					$new_comment =~ s/^\[(.*)\]$/$1/;
+					$new_comment =~ s/^\/\*(.*)\*\/$/$1/;
+
+					$new_comment = trim($new_comment);
+					$new_comment =~ s/^[^\w]$//; # Single lettered comment with non word character is usually a typo
+					$new_comment = "($new_comment)" if ($new_comment ne "");
+					my $new_email = format_email($email_name, $name_comment, $email_address, $new_comment);
+
+					if (WARN("BAD_SIGN_OFF",
+						 "Unexpected content after email: '$email', should be: '$new_email'\n" . $herecurr) &&
+					    $fix) {
+						$fixed[$fixlinenr] =~ s/\Q$email\E/$new_email/;
+					}
 				}
 			}