fix(api_helpers): re-add falcon.api_helpers (#1904)

docs/_newsfragments/1902.rst

@@ -0,0 +1,2 @@
+Re-add ``api_helpers`` module that was renamed ``app_helpers``.
+This module is considered deprecated, and will be removed in a future Falcon version.

falcon/api_helpers.py

@@ -0,0 +1,7 @@
+from .app_helpers import * # NOQA
+
+# TODO deprecate
+# import warnings
+# from .util.deprecation import DeprecatedWarning
+
+# warnings.warn('The api_helpers module was renamed to app_helpers.', DeprecatedWarning)

falcon/app_helpers.py

@@ -22,6 +22,13 @@
 from falcon.errors import CompatibilityError
 from falcon.util.sync import _wrap_non_coroutine_unsafe
 
+__all__ = (
+    'prepare_middleware',
+    'prepare_middleware_ws',
+    'default_serialize_error',
+    'CloseableStreamIterator'
+)
+
 
 def prepare_middleware(middleware, independent_middleware=False, asgi=False):
     """Check middleware interfaces and prepare the methods for request handling.

tests/test_deprecations.py

@@ -1,6 +1,30 @@
-from falcon import request_helpers, stream
+import pytest
+
+from falcon import app_helpers, request_helpers, stream
+
+# from _util import has_cython
 
 
 def test_bounded_stream():
     assert request_helpers.Body is stream.Body
     assert request_helpers.BoundedStream is stream.BoundedStream
+
+
+class TestApiHelpers:
+    @pytest.mark.filterwarnings('ignore:The api_helpers')
+    def test_imports(self):
+        from falcon import api_helpers
+
+        for name in app_helpers.__all__:
+            assert getattr(api_helpers, name) is getattr(app_helpers, name)
+
+    # TODO enable test of deprecation
+    # @pytest.mark.skipif(has_cython, reason='Reloading modules on Cython does not work')
+    # def test_warning(self):
+    #     import importlib
+
+    #     from falcon.util.deprecation import DeprecatedWarning
+
+    #     with pytest.warns(DeprecatedWarning, match='The api_helpers'):
+    #         from falcon import api_helpers
+    #         importlib.reload(api_helpers)