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fix recent messages by handling valueless and escaped irc tags

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The recent-messages API now serializes empty IRCv3 tags as bare keys
(e.g. `emotes`) instead of `emotes=`, which threw a RangeError in the
tag parser and silently dropped every recent message. Parse tags per the
IRCv3 spec: treat bare and empty values as equivalent, split on the first
`=` so values may contain `=`, and unescape values in a single pass
(\: \s \ \r \n). Also guard user extraction against prefixes without
`!`, and isolate per-message parse failures in _handleIRCData so one bad
message can no longer abort an entire batch.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
This commit is contained in:
Tommy Chow 2026-06-08 21:53:53 -07:00
parent 2b81f2cb31
commit c27a37d52f
4 changed files with 144 additions and 20 deletions
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89
lib/models/irc.dart
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@ -959,22 +959,25 @@ class IRCMessage {
// Obtain the index to break off the tags.
final tagAndIrcMessageDivider = whole.indexOf(' ');
// Get the tags substring and escape characters.
// IRC messages escape spaces with \s.
final tags = whole
.substring(1, tagAndIrcMessageDivider)
.replaceAll('\\s', ' ');
// Next, parse and map the tags.
// Parse the IRCv3 tags into a map. The tags section is everything between
// the leading '@' and the first space. We split on the *raw* string: a
// literal ';' is always a separator because escaped semicolons inside a
// value are encoded as `\:` (unescaped per-value below).
final mappedTags = <String, String>{};
final rawTags = whole.substring(1, tagAndIrcMessageDivider);
// Loop through each tag and store their key value pairs into the map.
for (final tag in tags.split(';')) {
// Skip if the tag has no value.
if (tag.endsWith('=')) continue;
for (final tag in rawTags.split(';')) {
// Split on the first '=' only — IRCv3 tag values may contain '='.
final equalsIndex = tag.indexOf('=');
final tagSplit = tag.split('=');
mappedTags[tagSplit[0]] = tagSplit[1];
// Skip valueless tags. Per the IRCv3 spec a missing value (bare `key`)
// and an empty value (`key=`) are equivalent — live Twitch sends the
// latter, the recent-messages API the former.
if (equalsIndex == -1 || equalsIndex == tag.length - 1) continue;
mappedTags[tag.substring(0, equalsIndex)] = _unescapeTagValue(
tag.substring(equalsIndex + 1),
);
}
// Now we'll parse the message itself.
@ -990,9 +993,19 @@ class IRCMessage {
// If the username exists, set it.
// tmi.twitch.tv means the message was sent by Twitch rather than a user, so will be irrelevant.
final String? user = splitMessage[0] == _twitchIrcServer
? mappedTags['login']
: splitMessage[0].substring(0, splitMessage[0].indexOf('!'));
final prefix = splitMessage[0];
final String? user;
if (prefix == _twitchIrcServer) {
user = mappedTags['login'];
} else {
// Normal prefixes are `nick!user@host`. Fall back to the login tag (or
// null) if the expected `!` is absent so an unexpected prefix shape can
// never throw a RangeError and take down the whole message.
final bangIndex = prefix.indexOf('!');
user = bangIndex == -1
? mappedTags['login']
: prefix.substring(0, bangIndex);
}
// If there is an associated message, set it.
String? message;
@ -1153,6 +1166,50 @@ class IRCMessage {
);
}
/// Unescapes an IRCv3 message-tag value.
///
/// The spec defines these sequences: `\:` → `;`, `\s` → space, `\\` → `\`,
/// `\r` → CR, `\n` → LF. Any other `\x` collapses to `x`, and a lone trailing
/// backslash is dropped. Done in a single pass so sequences can't be
/// double-unescaped (e.g. `\\s` correctly yields `\s`, not a space).
static String _unescapeTagValue(String value) {
// Fast path: the vast majority of tag values contain no escape sequences.
if (!value.contains('\\')) return value;
final buffer = StringBuffer();
for (var i = 0; i < value.length; i++) {
if (value[i] != '\\') {
buffer.write(value[i]);
continue;
}
// A trailing backslash with nothing after it is dropped.
if (i + 1 == value.length) break;
switch (value[i + 1]) {
case ':':
buffer.write(';');
break;
case 's':
buffer.write(' ');
break;
case '\\':
buffer.write('\\');
break;
case 'r':
buffer.write('\r');
break;
case 'n':
buffer.write('\n');
break;
default:
buffer.write(value[i + 1]);
}
i++; // Skip the escaped character we just consumed.
}
return buffer.toString();
}
factory IRCMessage.createNotice({
required String message,
VoidCallback? actionCallback,