Handle None in OTEL_PROPAGATORS (open-telemetry#4553)

Author: suauk

CHANGELOG.md

@@ -13,6 +13,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   ([#4508](https://github.com/open-telemetry/opentelemetry-python/pull/4508))
 - Fix serialization of extended attributes for logs signal
   ([#4342](https://github.com/open-telemetry/opentelemetry-python/pull/4342))
+- Handle OTEL_PROPAGATORS contains None
+  ([#4553](https://github.com/open-telemetry/opentelemetry-python/pull/4553))
 - docs: updated and added to the metrics and log examples
   ([#4559](https://github.com/open-telemetry/opentelemetry-python/pull/4559))
 
@@ -1531,8 +1533,6 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   Serialize tuple type values by coercing them into a string, since Jaeger does not
   support tuple types.
   ([#865](https://github.com/open-telemetry/opentelemetry-python/pull/865))
-- Validate span attribute types in SDK
-  ([#678](https://github.com/open-telemetry/opentelemetry-python/pull/678))
 - Specify to_json indent from arguments
   ([#718](https://github.com/open-telemetry/opentelemetry-python/pull/718))
 - Span.resource will now default to an empty resource

opentelemetry-api/src/opentelemetry/propagate/__init__.py

@@ -70,7 +70,7 @@ def example_route():
 
 from logging import getLogger
 from os import environ
-from typing import Optional
+from typing import List, Optional
 
 from opentelemetry.context.context import Context
 from opentelemetry.environment_variables import OTEL_PROPAGATORS
@@ -121,7 +121,7 @@ def inject(
     get_global_textmap().inject(carrier, context=context, setter=setter)
 
 
-propagators = []
+propagators: List[textmap.TextMapPropagator] = []
 
 # Single use variable here to hack black and make lint pass
 environ_propagators = environ.get(
@@ -132,12 +132,17 @@ def inject(
 
 for propagator in environ_propagators.split(","):
     propagator = propagator.strip()
-
+    if propagator.lower() == "none":
+        logger.debug(
+            "OTEL_PROPAGATORS environment variable contains none, removing all propagators"
+        )
+        propagators = []
+        break
     try:
-        propagators.append(  # type: ignore
+        propagators.append(
             next(  # type: ignore
                 iter(  # type: ignore
-                    entry_points(  # type: ignore
+                    entry_points(  # type: ignore[misc]
                         group="opentelemetry_propagator",
                         name=propagator,
                     )
@@ -153,7 +158,9 @@ def inject(
         raise
 
 
-_HTTP_TEXT_FORMAT = composite.CompositePropagator(propagators)  # type: ignore
+_HTTP_TEXT_FORMAT: textmap.TextMapPropagator = composite.CompositePropagator(
+    propagators
+)
 
 
 def get_global_textmap() -> textmap.TextMapPropagator:
@@ -164,4 +171,4 @@ def set_global_textmap(
     http_text_format: textmap.TextMapPropagator,
 ) -> None:
     global _HTTP_TEXT_FORMAT  # pylint:disable=global-statement
-    _HTTP_TEXT_FORMAT = http_text_format  # type: ignore
+    _HTTP_TEXT_FORMAT = http_text_format

opentelemetry-api/tests/propagators/test_propagators.py

@@ -49,6 +49,50 @@ def test_propagators(propagators):
 
         reload(opentelemetry.propagate)
 
+    @patch.dict(environ, {OTEL_PROPAGATORS: "None"})
+    @patch("opentelemetry.propagators.composite.CompositePropagator")
+    def test_none_propogators(self, mock_compositehttppropagator):
+        def test_propagators(propagators):
+            propagators = {propagator.__class__ for propagator in propagators}
+
+            self.assertEqual(len(propagators), 0)
+            self.assertEqual(
+                propagators,
+                set(),
+            )
+
+        mock_compositehttppropagator.configure_mock(
+            **{"side_effect": test_propagators}
+        )
+
+        # pylint: disable=import-outside-toplevel
+        import opentelemetry.propagate
+
+        reload(opentelemetry.propagate)
+
+    @patch.dict(environ, {OTEL_PROPAGATORS: "tracecontext, None"})
+    @patch("opentelemetry.propagators.composite.CompositePropagator")
+    def test_multiple_propogators_with_none(
+        self, mock_compositehttppropagator
+    ):
+        def test_propagators(propagators):
+            propagators = {propagator.__class__ for propagator in propagators}
+
+            self.assertEqual(len(propagators), 0)
+            self.assertEqual(
+                propagators,
+                set(),
+            )
+
+        mock_compositehttppropagator.configure_mock(
+            **{"side_effect": test_propagators}
+        )
+
+        # pylint: disable=import-outside-toplevel
+        import opentelemetry.propagate
+
+        reload(opentelemetry.propagate)
+
     @patch.dict(environ, {OTEL_PROPAGATORS: "a,  b,   c  "})
     @patch("opentelemetry.propagators.composite.CompositePropagator")
     @patch("opentelemetry.util._importlib_metadata.entry_points")