typing.Protocol + abc.ABC x 1.

This commit is the first in a commit chain supporting PEP 544-compliant
inheritance trees subclassing non-trivial combinations of the
`typing.Protocol` + `abc.ABC` superclasses, en-route to resolving beartype#117
kindly submitted by too-entertaining pun master @twoertwein (Torsten
Wörtwein). Specifically, this commit generalizes our test suite to test
the `typing.Literal` and `typing.Annotated` type hint factories against
the official `typing` module, the third-party `typing_extensions`
module, and the `beartype.typing` compatibility layer. Although doing
so admittedly has no relation whatsoever to this issue, every bug
resolution begins with a mild detour into the annals of inanity.
(*Undocumented acumen, man!*)

README.rst

@@ -29,7 +29,8 @@ GitHub Sponsors <beartype sponsorship_>`__:
 .. # well as the icon links below. kthx
 .. #    |icon-for-glorious-sponsor|
 
-* **Your iconic URL here.** Let us bestow you with eyeballs.
+* **Your iconic URL here.** `Let us bestow you with eyeballs <beartype
+  sponsorship_>`__.
 
 .. code-block:: bash
 

beartype/_util/hint/pep/proposal/pep484/utilpep484generic.py

@@ -418,8 +418,7 @@ def get_hint_pep484_generic_bases_unerased(hint: Any) -> tuple:
     if hint_bases is not None:
         return hint_bases
     # Else, this generic erased *NONE* of its superclasses. These superclasses
-    # *MUST* by definition be unerased and thus safely returnable as is. In
-    # this case...
+    # *MUST* by definition be unerased and thus safely returnable as is.
 
     # Unerased superclasses of this generic defined by the method resolution
     # order (MRO) for this generic.
@@ -428,7 +427,7 @@ def get_hint_pep484_generic_bases_unerased(hint: Any) -> tuple:
     # Substring prefixing all exceptions raised below.
     EXCEPTION_STR_PREFIX = (
         f'PEP 484 generic {repr(hint)} '
-        f'method resolution order {repr(hint_bases)}'
+        f'method resolution order {repr(hint_bases)} '
     )
 
     # If this MRO lists strictly less than four classes, raise an exception.
@@ -439,20 +438,20 @@ def get_hint_pep484_generic_bases_unerased(hint: Any) -> tuple:
     # * The "object" root superclass.
     if len(hint_bases) < 4:
         raise BeartypeDecorHintPep484Exception(
-            f'{EXCEPTION_STR_PREFIX} lists less than four classes.')
+            f'{EXCEPTION_STR_PREFIX}lists less than four classes.')
     # Else, this MRO lists at least four classes.
     #
     # If any class listed by this MRO fails to comply with the above
     # expectations, raise an exception.
     elif hint_bases[0] != hint:
         raise BeartypeDecorHintPep484Exception(
-            f'{EXCEPTION_STR_PREFIX} first item not {hint}.')
-    elif hint_bases[-2] != Generic:
-        raise BeartypeDecorHintPep484Exception(
-            f'{EXCEPTION_STR_PREFIX} second-to-last item not {Generic}.')
+            f'{EXCEPTION_STR_PREFIX}first item not {hint}.')
     elif hint_bases[-1] != object:
         raise BeartypeDecorHintPep484Exception(
-            f'{EXCEPTION_STR_PREFIX} last item not {object}.')
+            f'{EXCEPTION_STR_PREFIX}last item not {object}.')
+    elif hint_bases[-2] != Generic:
+        raise BeartypeDecorHintPep484Exception(
+            f'{EXCEPTION_STR_PREFIX}second-to-last item not {Generic}.')
     # Else, all classes listed by this MRO comply with the above expectations.
 
     # Return a slice of this tuple preserving *ONLY* the non-ignorable

beartype_test/a00_unit/data/hint/pep/proposal/_data_pep544.py

@@ -8,6 +8,11 @@
 '''
 
 # ....................{ TODO                              }....................
+#FIXME: Generalize this submodule to transparently test all hints against both
+#the "typing.Protocol" *AND* "beartype.typing.Protocol" superclasses. Doing so
+#will, in turn, require defining a new "HintPepMetadata.hints" instance
+#variable required to be a sequence of one or more hints.
+
 #FIXME: Test user-defined multiple-inherited protocols (i.e., user-defined
 #classes directly subclassing the "typing.Protocol" ABC and one or more other
 #superclasses) once @beartype supports these protocols as well.
@@ -36,6 +41,12 @@ def add_data(data_module: 'ModuleType') -> None:
 
     # If the active Python interpreter targets less than Python < 3.8, this
     # interpreter fails to support PEP 544. In this case, reduce to a noop.
+    #
+    # Note that we intentionally avoid testing against the
+    # "typing_extensions.Protocol" superclass. Why? Because that superclass is
+    # horribly broken under Python 3.7 and thus *CANNOT* be supported by
+    # beartype. This is why we only support a proper subset of
+    # "typing_extensions" attributes, folks.
     if not IS_PYTHON_AT_LEAST_3_8:
         return
     # Else, the active Python interpreter targets at least Python >= 3.8 and
@@ -45,6 +56,12 @@ def add_data(data_module: 'ModuleType') -> None:
     # Defer Python >= 3.8-specific imports.
     import pathlib
     from abc import abstractmethod
+    from beartype.typing import (
+        Any,
+        AnyStr,
+        TypeVar,
+        runtime_checkable,
+    )
     from beartype._data.hint.pep.sign.datapepsigns import HintSignGeneric
     from beartype_test.a00_unit.data.hint.util.data_hintmetacls import (
         HintPepMetadata,
@@ -53,9 +70,9 @@ def add_data(data_module: 'ModuleType') -> None:
     )
     from beartype_test.util.mod.pytmodtest import (
         is_package_beartype_vale_usable)
+
+    #FIXME: Generalize to iteratively import from "beartype.typing" as well.
     from typing import (
-        Any,
-        AnyStr,
         BinaryIO,
         IO,
         Protocol,
@@ -66,8 +83,6 @@ def add_data(data_module: 'ModuleType') -> None:
         SupportsInt,
         SupportsRound,
         TextIO,
-        TypeVar,
-        runtime_checkable,
     )
 
     # Type variables.