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re-assert
=========
show where your regex match assertion failed!
## usage
`re-assert` provides a helper class to make assertions of regexes simpler.
### `re_assert.Matches(pattern: str, *args, **kwargs)`
construct a `Matches` object.
_note_: under the hood, `re-assert` uses the [`regex`] library for matching,
any `*args` / `**kwargs` that `regex.compile` supports will work. in general,
the `regex` library is 100% compatible with the `re` library (and will even
accept its flags, etc.)
[`regex`]: https://pypi.org/project/regex/
### `re_assert.Matches.from_pattern(pattern: Pattern[str]) -> Matches`
construct a `Matches` object from an already-compiled regex.
this is useful (for instance) if you're testing an existing compiled regex.
```pycon
>>> import re
>>> reg = re.compile('foo')
>>> Matches.from_pattern(reg) == 'fork'
False
>>> Matches.from_pattern(reg) == 'food'
True
```
### `Matches.__eq__(other)` (`==`)
the equality operator is overridden for use with assertion frameworks such
as pytest
```pycon
>>> pat = Matches('foo')
>>> pat == 'bar'
False
>>> pat == 'food'
True
```
### `Matches.__repr__()` (`repr(...)`)
a side-effect of an equality failure changes the `repr(...)` of a `Matches`
object. this allows for useful pytest assertion messages:
```pytest
> assert Matches('foo') == 'fork'
E AssertionError: assert Matches('foo'...ork\n # ^ == 'fork'
E -Matches('foo')\n
E - # regex failed to match at:\n
E - #\n
E - #> fork\n
E - # ^
E +'fork'
```
### `Matches.assert_matches(s: str)`
if you're using some other test framework, this method is useful for producing
a readable traceback
```pycon
>>> Matches('foo').assert_matches('food')
>>> Matches('foo').assert_matches('fork')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/home/asottile/workspace/re-assert/re_assert.py", line 63, in assert_matches
assert self == s, self._fail
AssertionError: regex failed to match at:
> fork
^
```
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