Make entry_points behave the same across Python versions

Fixes open-telemetry#3167

Author: ocelotl

opentelemetry-api/src/opentelemetry/util/_importlib_metadata.py

@@ -17,22 +17,51 @@
 # FIXME remove this when support for 3.7 is dropped.
 if version_info.minor == 7:
     # pylint: disable=import-error
-    from importlib_metadata import entry_points, version  # type: ignore
+    from importlib_metadata import (  # type: ignore
+        EntryPoint,
+        entry_points,
+        version,
+    )
 
 # FIXME remove this file when support for 3.9 is dropped.
 elif version_info.minor in (8, 9):
     # pylint: disable=import-error
+    from importlib.metadata import EntryPoint
     from importlib.metadata import (
         entry_points as importlib_metadata_entry_points,
     )
     from importlib.metadata import version
 
-    def entry_points(group: str, name: str):  # type: ignore
+    def entry_points(group: str = None, name: str = None):  # type: ignore
+
+        if group is None:
+            return importlib_metadata_entry_points()
+
+        if name is None:
+            return importlib_metadata_entry_points()[group]
+
         for entry_point in importlib_metadata_entry_points()[group]:
             if entry_point.name == name:
-                yield entry_point
+                return [entry_point]
+
+    __all__ = [
+        "entry_points",
+        "version",
+    ]
 
 else:
-    from importlib.metadata import entry_points, version
+    from importlib.metadata import (
+        EntryPoint,
+        EntryPoints,
+        SelectableGroups,
+        entry_points,
+        version,
+    )
 
-__all__ = ["entry_points", "version"]
+    __all__ = [
+        "entry_points",
+        "version",
+        "EntryPoint",
+        "SelectableGroups",
+        "EntryPoints",
+    ]

opentelemetry-api/tests/util/test__importlib_metadata.py

@@ -13,9 +13,13 @@
 # limitations under the License.
 
 from unittest import TestCase
+from warnings import catch_warnings, filterwarnings
 
 from opentelemetry.metrics import MeterProvider
-from opentelemetry.util._importlib_metadata import entry_points
+from opentelemetry.util._importlib_metadata import EntryPoint
+from opentelemetry.util._importlib_metadata import (
+    entry_points as entry_points_function,  # SelectableGroups,; EntryPoints
+)
 
 
 class TestEntryPoints(TestCase):
@@ -24,11 +28,67 @@ def test_entry_points(self):
         self.assertIsInstance(
             next(
                 iter(
-                    entry_points(
+                    entry_points_function(
                         group="opentelemetry_meter_provider",
                         name="default_meter_provider",
                     )
                 )
             ).load()(),
             MeterProvider,
         )
+
+    def test_uniform_behavior(self):
+        """
+        Test that entry_points behaves the same regardless of the Python
+        version.
+        """
+
+        selectable_groups = entry_points_function()
+
+        # self.assertIsInstance(selectable_groups, SelectableGroups)
+
+        # Supressing the following warning here:
+        # DeprecationWarning: SelectableGroups dict interface is deprecated. Use select.
+        # The behavior of the importlib metadata library is hard to understand,
+        # this is True: selectable_groups is selectable_groups.select(). So,
+        # using select, as the warning says yields the same problem. Also
+        # select does not accept any parameters.
+
+        with catch_warnings():
+            filterwarnings("ignore", category=DeprecationWarning)
+            entry_points = selectable_groups.select()[
+                "opentelemetry_propagator"
+            ]
+
+        # Supressing the following warning here:
+        # DeprecationWarning: DeprecationWarning: Accessing entry points by index is deprecated. Cast to tuple if needed.
+        # The behavior of the importlib metadata library is hard to understand,
+        # this is True: entry_points == .select(). So, using select, as the
+        # warning says yields the same problem. Also select does not accept any
+        # parameters.
+        with catch_warnings():
+            filterwarnings("ignore", category=DeprecationWarning)
+
+            self.assertIsInstance(entry_points.select()[0], EntryPoint)
+
+            entry_points = entry_points_function(
+                group="opentelemetry_propagator"
+            )
+
+            self.assertIsInstance(entry_points.select()[0], EntryPoint)
+
+            entry_points = entry_points_function(
+                group="opentelemetry_propagator", name="baggage"
+            )
+
+            self.assertIsInstance(entry_points.select()[0], EntryPoint)
+
+        entry_points = entry_points_function(group="abc")
+
+        self.assertEqual(entry_points, [])
+
+        entry_points = entry_points_function(
+            group="opentelemetry_propagator", name="abc"
+        )
+
+        self.assertEqual(entry_points, [])