otel-shim: Adding test for empty context from extract

ext/opentelemetry-ext-opentracing-shim/src/opentelemetry/ext/opentracing_shim/__init__.py

@@ -700,6 +700,10 @@ def get_as_list(dict_object, key):
 
         propagator = propagators.get_global_httptextformat()
         ctx = propagator.extract(get_as_list, carrier)
-        otel_context = trace_api.get_current_span(ctx).get_context()
+        span = trace_api.get_current_span(ctx)
+        if span is not None:
+            otel_context = span.get_context()
+        else:
+            otel_context = trace_api.INVALID_SPAN_CONTEXT
 
         return SpanContextShim(otel_context)

ext/opentelemetry-ext-opentracing-shim/tests/test_shim.py

@@ -24,7 +24,10 @@
 from opentelemetry import propagators, trace
 from opentelemetry.ext.opentracing_shim import util
 from opentelemetry.sdk.trace import TracerProvider
-from opentelemetry.test.mock_httptextformat import MockHTTPTextFormat
+from opentelemetry.test.mock_httptextformat import (
+    MockHTTPTextFormat,
+    NOOPHTTPTextFormat,
+)
 
 
 class TestShim(TestCase):
@@ -515,6 +518,20 @@ def test_extract_http_headers(self):
         self.assertEqual(ctx.unwrap().trace_id, 1220)
         self.assertEqual(ctx.unwrap().span_id, 7478)
 
+    def test_extract_empty_context_returns_invalid_context(self):
+        """In the case where the propagator cannot extract a
+        SpanContext, extract should return and invalid span context.
+        """
+        _old_propagator = propagators.get_global_httptextformat()
+        propagators.set_global_httptextformat(NOOPHTTPTextFormat())
+        try:
+            carrier = {}
+
+            ctx = self.shim.extract(opentracing.Format.HTTP_HEADERS, carrier)
+            self.assertEqual(ctx.unwrap(), trace.INVALID_SPAN_CONTEXT)
+        finally:
+            propagators.set_global_httptextformat(_old_propagator)
+
     def test_extract_text_map(self):
         """Test `extract()` method for Format.TEXT_MAP."""
 

opentelemetry-sdk/src/opentelemetry/sdk/trace/__init__.py

@@ -747,10 +747,6 @@ def get_tracer(
             ),
         )
 
-    @staticmethod
-    def get_current_span() -> Span:
-        return trace_api.get_current_span()
-
     def add_span_processor(self, span_processor: SpanProcessor) -> None:
         """Registers a new :class:`SpanProcessor` for this `TracerProvider`.
 

tests/util/src/opentelemetry/test/mock_httptextformat.py

@@ -15,7 +15,7 @@
 import typing
 
 from opentelemetry import trace
-from opentelemetry.context import Context
+from opentelemetry.context import Context, get_current
 from opentelemetry.trace.propagation import (
     get_current_span,
     set_span_in_context,
@@ -28,6 +28,30 @@
 )
 
 
+class NOOPHTTPTextFormat(HTTPTextFormat):
+    """A propagator that does not extract nor inject.
+
+    This class is useful for catching edge cases assuming
+    a SpanContext will always be present.
+    """
+
+    def extract(
+        self,
+        get_from_carrier: Getter[HTTPTextFormatT],
+        carrier: HTTPTextFormatT,
+        context: typing.Optional[Context] = None,
+    ) -> Context:
+        return get_current()
+
+    def inject(
+        self,
+        set_in_carrier: Setter[HTTPTextFormatT],
+        carrier: HTTPTextFormatT,
+        context: typing.Optional[Context] = None,
+    ) -> None:
+        return None
+
+
 class MockHTTPTextFormat(HTTPTextFormat):
     """Mock propagator for testing purposes."""