Remove circular testslide imports

Summary:
While testing the import cost for some binaries I've found out that testslide is providing an implicit circular import.
An example is `testslide.mock_constructor` importing `testslide`.

This is not necessarily an issue, but I would love to improve it.

In the general case the `testslide` import was needed:
* to make `testslide._importer` available, I'm fixing it via a local import
* to have `testslide.__file__`, even in this case a local import would be sufficient

Differential Revision: D51025476

fbshipit-source-id: b3292393137c01a6a64b29d620dadb001a989260

testslide/mock_callable.py

@@ -22,7 +22,6 @@
 )
 from unittest.mock import Mock
 
-import testslide
 from testslide.lib import _validate_return_type, _wrap_signature_and_type_validation
 from testslide.strict_mock import StrictMock
 
@@ -833,7 +832,8 @@ def __init__(
         self._allow_coro = False
         self._accept_partial_call = False
         if isinstance(target, str):
-            self._target = testslide._importer(target)
+            from testslide import _importer
+            self._target = _importer(target)
         else:
             self._target = target
 

testslide/mock_constructor.py

@@ -5,7 +5,6 @@
 import inspect
 from typing import Any, Callable, Dict, List, Optional, Tuple, Type, Union
 
-import testslide
 from testslide.mock_callable import _CallableMock, _MockCallableDSL
 
 from .lib import (
@@ -331,7 +330,8 @@ def mock_constructor(
         raise ValueError("Second argument must be a string with the name of the class.")
     _bail_if_private(class_name, allow_private)
     if isinstance(target, str):
-        target = testslide._importer(target)
+        from testslide import _importer
+        target = _importer(target)
     target_class_id = (id(target), class_name)
 
     if target_class_id in _mocked_target_classes:

testslide/patch_attribute.py

@@ -5,8 +5,7 @@
 
 from typing import Any, Callable, Dict, Tuple
 
-import testslide
-from testslide.strict_mock import UndefinedAttribute
+from testslide.strict_mock import StrictMock, UndefinedAttribute
 
 from .lib import _bail_if_private, _validate_argument_type
 from .patch import _patch
@@ -55,11 +54,12 @@ def patch_attribute(
     _bail_if_private(attribute, allow_private)
 
     if isinstance(target, str):
-        target = testslide._importer(target)
+        from testslide import _importer
+        target = _importer(target)
 
     key = (id(target), attribute)
 
-    if isinstance(target, testslide.StrictMock):
+    if isinstance(target, StrictMock):
         if not type_validation:
             target.__dict__["_attributes_to_skip_type_validation"].append(attribute)
         template_class = target._template

testslide/runner.py

@@ -33,8 +33,6 @@
     Whitespace,
 )
 
-import testslide
-
 from . import AggregatedExceptions, Context, Example, Skip, _ExampleRunner
 
 ##
@@ -281,7 +279,10 @@ def print_cyan_dim_underline(self, *values: Any, **kwargs: Any) -> None:
 
 
 class FailurePrinterMixin(ColorFormatterMixin):
-    TESTSLIDE_PATH: str = os.path.abspath(os.path.dirname(testslide.__file__))
+    @property
+    def TESTSLIDE_PATH(self) -> str:
+        from testslide import __file__
+        return os.path.abspath(os.path.dirname(__file__))
 
     def _get_test_module_index(self, tb: traceback.StackSummary) -> Optional[int]:
         test_module_paths = [