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"""Internal implementation of helper types for Sum annotations.""" |
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import ast |
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import typing |
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import weakref |
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import astor # type: ignore |
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_CTOR_CACHE: typing.Dict[typing.Tuple, "Ctor"] = {} |
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ARGS: typing.MutableMapping[ |
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typing.Union["Ctor", typing.Type["Ctor"]], typing.Tuple |
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] = weakref.WeakKeyDictionary() |
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class Ctor: |
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"""Marker class for adt constructors. |
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To use, index with a sequence of types, and annotate a variable in an |
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adt-decorated class with it. |
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""" |
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__slots__ = ("__weakref__",) |
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def __new__(cls, args): |
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if args == (): |
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return cls |
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self = object.__new__(cls) |
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ARGS[self] = args |
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return _CTOR_CACHE.setdefault(args, self) |
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def __init_subclass__(cls, **kwargs): |
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raise TypeError |
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def __class_getitem__(cls, args): |
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if not isinstance(args, tuple): |
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args = (args,) |
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# Yes it is. |
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return cls(args) # pylint: disable=not-callable |
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ARGS[Ctor] = () |
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def _interpret_args_from_non_string( |
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constructor: typing.Any |
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) -> typing.Optional[typing.Tuple]: |
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try: |
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return ARGS.get(constructor) |
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except TypeError: |
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return None |
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def _interpret_classvar_from_non_string(annotation: typing.Any) -> bool: |
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if annotation is typing.ClassVar: |
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return True |
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try: |
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return annotation.__origin__ is typing.ClassVar |
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except AttributeError: |
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return False |
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def _parse_constructor(constructor: str) -> ast.Module: |
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try: |
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return ast.parse(constructor, mode="eval") |
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except Exception: |
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raise ValueError("parsing annotation failed") |
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def _get_args_from_index(index: ast.AST) -> typing.Tuple: |
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if isinstance(index, ast.Tuple): |
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return tuple(astor.to_source(elt) for elt in index.elts) |
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return (astor.to_source(index),) |
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def _checked_eval(source, global_ns: typing.Dict[str, typing.Any]) -> typing.Any: |
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try: |
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# Oh no, the user might end up executing arbitrary code that they wrote |
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# in the first place. |
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return eval(source, global_ns) # pylint: disable=eval-used |
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# If we hit this, anything could have gone wrong, but just assume it's not |
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# anything we care about. |
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except Exception: # pylint: disable=broad-except |
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return None |
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NO_VALUE = object() |
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def _extract_tuple_ast( |
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constructor: str, global_ns: typing.Dict[str, typing.Any] |
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) -> typing.Optional[typing.Tuple]: |
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ctor_ast = _parse_constructor(constructor) |
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value = index = NO_VALUE |
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if isinstance(ctor_ast.body, ast.Subscript) and isinstance( |
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ctor_ast.body.slice, ast.Index |
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): |
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index = ctor_ast.body.slice.value |
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ctor_ast.body = ctor_ast.body.value |
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value = _checked_eval(compile(ctor_ast, "<annotation>", "eval"), global_ns) |
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if value is Ctor: |
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# If value is Ctor, then value was set, which is only possible if the |
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# previous block executed, which will set "index" to an AST. |
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return _get_args_from_index(typing.cast(ast.AST, index)) |
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if value is None: |
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return None |
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return _interpret_args_from_non_string(_checked_eval(constructor, global_ns)) |
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def _str_is_classvar(annotation: str, global_ns: typing.Dict[str, typing.Any]) -> bool: |
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annotation_ast = _parse_constructor(annotation) |
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value = NO_VALUE |
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if isinstance(annotation_ast.body, ast.Subscript) and isinstance( |
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annotation_ast.body.slice, ast.Index |
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): |
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annotation_ast.body = annotation_ast.body.value |
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value = _checked_eval( |
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compile(annotation_ast, "<annotation>", "eval"), global_ns |
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) |
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if value is typing.ClassVar: |
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return True |
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if value is None: |
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return False |
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return _interpret_classvar_from_non_string(_checked_eval(annotation, global_ns)) |
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def get_args( |
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constructor, global_ns: typing.Dict[str, typing.Any] |
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) -> typing.Optional[typing.Tuple]: |
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"""Given annotation value and module namespace, return Ctor args, if any. |
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The function first checks if the value is a string. If so, it tries to |
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parse it. |
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Otherwise, if the value is a Ctor instance, it extracts the annotation, and |
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if not, it returns ``None``. |
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""" |
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if isinstance(constructor, str): |
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try: |
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return _extract_tuple_ast(constructor, global_ns) |
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except ValueError: |
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return None |
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return _interpret_args_from_non_string(constructor) |
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def annotation_is_classvar(annotation, global_ns: typing.Dict[str, typing.Any]) -> bool: |
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if isinstance(annotation, str): |
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try: |
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return _str_is_classvar(annotation, global_ns) |
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except ValueError: |
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return False |
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return _interpret_classvar_from_non_string(annotation) |
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mwchase /
python-structured-data
