Regex flag have an unexpected behavior

[Heziode]

Describe the bug

Regex flag do not capture the last character when it is a closing parenthesis.
Regex flag do not capture well pattern inside { and }.

To Reproduce

Steps to reproduce the behavior:

I add this regex flag: regex:"((?:@:\(|\{)[^\)\}]+(?:\)|\}))"
Testing string: @:(foo.bar.baz) | @:(hello.world) | {foo32}
Check on regex101: https://regex101.com/r/SZVYGO/1

Expected behavior

Regex flag do capture the last character when it is a closing parenthesis.
Regex flag do capture well pattern inside { and }.

Screenshots

Server configuration and status

docker-compose exec weblate weblate list_versions:

• Weblate: 4.1.1
• Django: 3.0.7
• siphashc: 1.3
• Whoosh: 2.7.4
• translate-toolkit: 3.0.0
• lxml: 4.5.1
• Pillow: 7.1.2
• bleach: 3.1.5
• python-dateutil: 2.8.1
• social-auth-core: 3.3.3
• social-auth-app-django: 3.4.0
• django-crispy-forms: 1.9.1
• oauthlib: 3.1.0
• django-compressor: 2.4
• djangorestframework: 3.11.0
• django-filter: 2.3.0
• django-appconf: 1.0.4
• user-agents: 2.1
• filelock: 3.0.12
• setuptools: 40.8.0
• jellyfish: 0.8.2
• openpyxl: 3.0.1
• celery: 4.4.5
• kombu: 4.6.10
• translation-finder: 2.1
• html2text: 2020.1.16
• pycairo: 1.16.2
• pygobject: 3.30.4
• diff-match-patch: 20181111
• requests: 2.24.0
• django-redis: 4.12.1
• hiredis: 1.0.1
• sentry_sdk: 0.15.1
• Cython: 0.29.20
• misaka: 2.1.1
• GitPython: 3.1.3
• borgbackup: 1.1.13
• pyparsing: 2.4.7
• Python: 3.7.3
• Git: 2.20.1
• psycopg2: 2.8.5
• psycopg2-binary: 2.8.5
• phply: 1.2.5
• chardet: 3.0.4
• ruamel.yaml: 0.16.10
• tesserocr: 2.5.1
• akismet: 1.1
• boto3: 1.14.6
• zeep: 3.4.0
• aeidon: 1.7.0
• iniparse: 0.5
• mysqlclient: 1.4.6
• Mercurial: 5.4.1
• git-svn: 2.20.1
• git-review: 1.28.0
• hub: 2.13.0
• lab: 0.16
• Redis server: 4.0.14
• PostgreSQL server: 11.8
• Database backends: django.db.backends.postgresql
• Cache backends: default:RedisCache, avatar:FileBasedCache
• Email setup: django.core.mail.backends.smtp.EmailBackend: mailu_front
• OS encoding: filesystem=utf-8, default=utf-8
• Celery: redis://cache:6379/1, redis://cache:6379/1, regular
• Platform: Linux 4.19.128-xxxx-std-ipv6-64 (x86_64)

Weblate deploy checks

docker-compose exec --user weblate weblate weblate check --deploy:

SystemCheckError: System check identified some issues:

CRITICALS:
?: (weblate.E003) Cannot send e-mail ([Errno -2] Name or service not known), please check EMAIL_* settings.
	HINT: https://docs.weblate.org/en/weblate-4.1.1/admin/install.html#out-mail

WARNINGS:
?: (security.W005) You have not set the SECURE_HSTS_INCLUDE_SUBDOMAINS setting to True. Without this, your site is potentially vulnerable to attack via an insecure connection to a subdomain. Only set this to True if you are certain that all subdomains of your domain should be served exclusively via SSL.

INFOS:
?: (weblate.I021) Error collection is not set up, it is highly recommended for production use
	HINT: https://docs.weblate.org/en/weblate-4.1.1/admin/install.html#collecting-errors
?: (weblate.I028) Backups are not configured, it is highly recommended for production use
	HINT: https://docs.weblate.org/en/weblate-4.1.1/admin/backup.html
?: (weblate.I031) New Weblate version is available, please upgrade to 4.2.2.
	HINT: https://docs.weblate.org/en/weblate-4.1.1/admin/upgrade.html

System check identified 5 issues (1 silenced).

[nijel]

The problem here is that flag parsing handles escape sequences as well, so your expression is parsed as: ((?:@:(|{)[^)}]+(?:)|}))

This matches exactly what you observe: https://regex101.com/r/O9zVx5/1

Such behavior is probably not desired, I will look whether it's possible to address this (especially whether something else relies in this behavior).

[Heziode]

The problem here is that flag parsing handles escape sequences as well, so your expression is parsed as: ((?:@:(|{)[^)}]+(?:)|}))

Exact !

Furthermore, it's planed to add regex support for placeholders ?

[nijel]

Furthermore, it's planed to add regex support for placeholders ?

No, feel free to create separate issue for that.

[github-actions]

The issue you have reported seems to be resolved now.

• In case you see a similar problem, please open a separate issue.
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