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# Copyright 2017 The Chromium Authors
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.
"""Regular expression helpers."""
import re
def _CreateIdentifierRegex(parts):
assert parts
if parts[0]:
# Allow word boundary or a _ prefix.
prefix_pattern = r'\b_?'
else:
# Allow word boundary, _, or a case transition.
prefix_pattern = r'(?:\b|(?<=_)|(?<=[a-z])(?=[A-Z]))'
parts = parts[1:]
assert parts
if parts[-1]:
# Allow word boundary, trailing _, or single trailing digit.
suffix_pattern = r'\d?_?\b'
else:
# Allow word boundary, _, or a case transition.
suffix_pattern = r'(?:\b|(?=_|\d)|(?<=[a-z])(?=[A-Z]))'
parts = parts[:-1]
assert parts
shouty_pattern = '_'.join(a.upper() for a in parts)
snake_pattern = '_'.join(a.lower() for a in parts)
camel_remainder = parts[0][1:]
for token in parts[1:]:
camel_remainder += token.title()
first_letter = parts[0][0]
prefixed_pattern = '[a-z]' + first_letter.upper() + camel_remainder
camel_pattern = '[%s%s]%s' % (first_letter.lower(), first_letter.upper(),
camel_remainder)
middle_patterns = '|'.join(
(shouty_pattern, snake_pattern, prefixed_pattern, camel_pattern))
return r'(?:%s(?:%s)%s)' % (prefix_pattern, middle_patterns, suffix_pattern)
def ExpandRegexIdentifierPlaceholder(pattern):
"""Expands {{identifier}} within a given regular expression.
Returns |pattern|, with the addition that {{some_name}} is expanded to match:
SomeName, kSomeName, SOME_NAME, etc.
To match part of a name, use {{_some_name_}}. This will additionally match:
kPrefixSomeNameSuffix, PREFIX_SOME_NAME_SUFFIX, etc.
Note: SymbolGroup.Where* methods call this function already, so there is
generally no need to call it directly.
"""
return re.sub(r'\{\{(.*?)\}\}',
lambda m: _CreateIdentifierRegex(m.group(1).split('_')),
pattern)
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