Validating "slug" and deny line ending and the end.

[jedie]

A "slug" regular expression can look like this: r'^[-a-zA-Z0-9_]+\Z'

But \Z can't be used in JSON schema, because the regular expression syntax used from JavaScript and they doesn't support \Z.
Other libraries like https://github.com/swaggest/php-json-schema has a check for this case, e.g.:

        if (substr($data, -2) === '\Z') {
            return 'Invalid regex: \Z is not supported';
        }

https://github.com/swaggest/php-json-schema/blob/2d7b8e22a9de2680b8639404502df0b24b834da6/src/Constraint/Format.php#L111-L113

This is missing in jsonschema.

If we replace \Z with $ (e.g.: r'^[-a-zA-Z0-9_]+\Z') then a string with line ending like foo\n is valid because jsonschema seems not use use re.DOTALL, isn't it?

Or did i miss something?

tl;td;

• \Z should not be accepted
• re.DOTALL should be used for regex

[Julian]

The specification recommends but does not require you use JavaScript syntax. In particular, if you know all the consumers of your schema it may be you want to use Python syntax, and/or to put your flag inside the regex.

[jedie]

Yes, but one of our schema consumer is a PHP project ;) So we can't use \Z :(

[Julian]

I'm not sure what else to offer then, you need to pick a common subset of regex syntax that works for what you're using.

\Z is valid in Python, so there's no reason to disallow it, and re.DOTALL isn't the default in Python so there's no reason to enable it, but you're welcome to enable it inside your own regex if you want it on and your other consumers are OK with it.

Otherwise you might be interested in #1142 but that's something off in the future, and you'd still need to find a PHP regex implementation for Python or a JS implementation for PHP.

[jedie]

you're welcome to enable it inside your own regex

Oh, is this possible? How?

[Julian]

See https://docs.python.org/3/library/re.html#regular-expression-syntax, specifically (?s) IIRC.

[jedie]

See https://docs.python.org/3/library/re.html#regular-expression-syntax, specifically (?s) IIRC.

EDIT: I tested r'(?s)^[-a-zA-Z0-9_]+$' but foo\n is still valid. Thus, my statement that DOTALL is a solution is false :(

I don't see a way to solve the problem.