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#!/usr/bin/env python3
# --------------------( LICENSE )--------------------
# Copyright (c) 2014-2025 Beartype authors.
# See "LICENSE" for further details.
'''
Project-wide **Python identifier utilities** (i.e., low-level callables handling
unqualified and qualified attribute, callable, class, module, and variable
names).
This private submodule is *not* intended for importation by downstream callers.
'''
# ....................{ IMPORTS }....................
from beartype.roar._roarexc import _BeartypeUtilTextIdentifierException
from beartype._data.typing.datatyping import TypeException
# ....................{ RAISERS }....................
def die_unless_identifier(
# Mandatory parameters.
text: str,
# Optional parameters.
exception_cls: TypeException = _BeartypeUtilTextIdentifierException,
exception_prefix: str = '',
) -> None:
'''
Raise an exception unless the passed string is a valid **Python attribute
name** (i.e., ``.``-delimited concatenation of one or more
:pep:`3131`-compliant syntactically valid Python identifiers, including the
names of attributes, callables, classes, modules, and variables).
Parameters
----------
text : str
String to be validated.
exception_cls : Type[Exception]
Type of exception to be raised in the event of a fatal error. Defaults
to :exc:`._BeartypeUtilTextIdentifierException`.
exception_prefix : str, optional
Human-readable label prefixing the representation of this string in the
exception message. Defaults to the empty string.
Raises
------
exception_cls
If this string is *not* a valid Python attribute name.
See Also
--------
:func:`.is_identifier`
Further details.
'''
# If this string is *NOT* a valid Python attribute name, raise an exception.
if not (isinstance(text, str) and is_identifier(text)):
assert isinstance(exception_cls, type), (
'f{repr(exception_cls)} not exception class.')
assert isinstance(exception_prefix, str), (
'f{repr(exception_prefix)} not string.')
raise exception_cls(
f'{exception_prefix}{repr(text)} not valid Python attribute name.')
# Else, this string is a valid Python attribute name.
# ....................{ TESTERS }....................
def is_dunder(text: str) -> bool:
'''
:data:`True` only if the passed string vaguely conforms to the name of a
**dunder attribute** (i.e., attribute whose name is both prefixed and
suffixed by ``"__"`` double underscore substrings).
Parameters
----------
text : str
String to be inspected.
Returns
-------
bool
:data:`True` only if this string conforms to a dunder attribute name.
'''
assert isinstance(text, str), f'{repr(text)} not string.'
#FIXME: *INSUFFICIENT.* We also need to call is_identifier() here. *sigh*
# Return us up the powerful one-liner of power.
return text.startswith('__') and text.endswith('__')
def is_identifier(text: str) -> bool:
'''
:data:`True` only if the passed string is a valid **Python attribute name**
(i.e., ``.``-delimited concatenation of one or more :pep:`3131`-compliant
syntactically valid Python identifiers, including the names of attributes,
callables, classes, modules, and variables).
This tester is suitable for detecting whether this string is the
fully-qualified name of an arbitrary Python object.
Caveats
-------
**This tester is mildly slow,** due to unavoidably splitting this string on
``.`` delimiters and iteratively passing each of the split substrings to
the :meth:`str.isidentifier` builtin. Due to the following caveat, this
inefficiency is unavoidable.
**This tester is not optimizable with regular expressions** -- at least,
not trivially. Technically, this tester *can* be optimized by leveraging
the "General Category" of Unicode filters provided by the third-party
:mod:`regex` package. Practically, doing so would require the third-party
:mod:`regex` package and would still almost certainly fail in edge cases.
Why? Because Python 3 permits Python identifiers to contain Unicode letters
and digits in the "General Category" of Unicode code points, which is
extremely non-trivial to match with the standard :mod:`re` module.
Parameters
----------
text : str
String to be inspected.
Returns
-------
bool
:data:`True` only if this string is the ``.``-delimited concatenation of
one or more syntactically valid Python identifiers.
'''
assert isinstance(text, str), f'{repr(text)} not string.'
# If this text contains *NO* "." delimiters and is thus expected to be an
# unqualified Python identifier, return true only if this is the case.
if '.' not in text:
return text.isidentifier()
# Else, this text contains one or more "." delimiters and is thus expected
# to be a qualified Python identifier.
# Return true only if *ALL* "."-delimited substrings split from this string
# are valid unqualified Python identifiers. Note that:
# * Regular expressions report false negatives. See the docstring.
# * Manual iteration is significantly faster than "all(...)"- and
# "any(...)"-style comprehensions.
# * This approach correctly handles *ALL* edge cases, including when:
# * This string is simply the "." character. In this case:
# >>> '.'.split('.')
# ['', '']
# Since the empty string is *NOT* a valid Python identifier, this
# iteration immediately returns false as expected.
# * There exists an alternative and significantly more computationally
# expensive means of testing this condition, employed by the
# typing.ForwardRef.__init__() method to valid the validity of the passed
# relative classname:
# # Needless to say, we'll never be doing this.
# try:
# all(
# compile(identifier, '<string>', 'eval')
# for identifier in text.split('.')
# )
# return True
# except SyntaxError:
# return False
for text_basename in text.split('.'):
# If this "."-delimited substring is *NOT* a valid unqualified Python
# identifier, return false.
if not text_basename.isidentifier():
return False
# Else, this "."-delimited substring is a valid unqualified Python
# identifier. In this case, silently continue to the next.
# Return true, since *ALL* "."-delimited substrings split from this string
# are valid unqualified Python identifiers.
return True
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