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rust-matchers: improve `Matcher` trait ergonomics...
rust-matchers: improve `Matcher` trait ergonomics `VisitChildrenSet` has no need to own the set, this will save allocations. The `file_set` return type change is motivated by both ergonomics and... being able to compile code. The `AlwaysMatcher` does not store a `file_set`, which requires it to return an owned `HashSet`, which in turn would change our return type to `Cow<&HgPath>` (lifetimes omitted). This is both un-ergonomic and troublesome for more complex lifetime issues (especially with the upcoming `FileMatcher` in the following patch). Differential Revision: https://phab.mercurial-scm.org/D7525

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converters.py
24 lines | 531 B | text/x-python | PythonLexer
"""
Commonly useful converters.
"""
from __future__ import absolute_import, division, print_function
def optional(converter):
"""
A converter that allows an attribute to be optional. An optional attribute
is one which can be set to ``None``.
:param callable converter: the converter that is used for non-``None``
values.
.. versionadded:: 17.1.0
"""
def optional_converter(val):
if val is None:
return None
return converter(val)
return optional_converter