Initial commit

.venv/lib/python3.9/site-packages/attr/converters.py

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+"""
+Commonly useful converters.
+"""
+
+from __future__ import absolute_import, division, print_function
+
+from ._compat import PY2
+from ._make import NOTHING, Factory, pipe
+
+
+if not PY2:
+    import inspect
+    import typing
+
+
+__all__ = [
+    "pipe",
+    "optional",
+    "default_if_none",
+]
+
+
+def optional(converter):
+    """
+    A converter that allows an attribute to be optional. An optional attribute
+    is one which can be set to ``None``.
+
+    Type annotations will be inferred from the wrapped converter's, if it
+    has any.
+
+    :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)
+
+    if not PY2:
+        sig = None
+        try:
+            sig = inspect.signature(converter)
+        except (ValueError, TypeError):  # inspect failed
+            pass
+        if sig:
+            params = list(sig.parameters.values())
+            if params and params[0].annotation is not inspect.Parameter.empty:
+                optional_converter.__annotations__["val"] = typing.Optional[
+                    params[0].annotation
+                ]
+            if sig.return_annotation is not inspect.Signature.empty:
+                optional_converter.__annotations__["return"] = typing.Optional[
+                    sig.return_annotation
+                ]
+
+    return optional_converter
+
+
+def default_if_none(default=NOTHING, factory=None):
+    """
+    A converter that allows to replace ``None`` values by *default* or the
+    result of *factory*.
+
+    :param default: Value to be used if ``None`` is passed. Passing an instance
+       of `attr.Factory` is supported, however the ``takes_self`` option
+       is *not*.
+    :param callable factory: A callable that takes no parameters whose result
+       is used if ``None`` is passed.
+
+    :raises TypeError: If **neither** *default* or *factory* is passed.
+    :raises TypeError: If **both** *default* and *factory* are passed.
+    :raises ValueError: If an instance of `attr.Factory` is passed with
+       ``takes_self=True``.
+
+    .. versionadded:: 18.2.0
+    """
+    if default is NOTHING and factory is None:
+        raise TypeError("Must pass either `default` or `factory`.")
+
+    if default is not NOTHING and factory is not None:
+        raise TypeError(
+            "Must pass either `default` or `factory` but not both."
+        )
+
+    if factory is not None:
+        default = Factory(factory)
+
+    if isinstance(default, Factory):
+        if default.takes_self:
+            raise ValueError(
+                "`takes_self` is not supported by default_if_none."
+            )
+
+        def default_if_none_converter(val):
+            if val is not None:
+                return val
+
+            return default.factory()
+
+    else:
+
+        def default_if_none_converter(val):
+            if val is not None:
+                return val
+
+            return default
+
+    return default_if_none_converter