distro: fix auto instrumentation with otlp OTEL_TRACES_EXPORTER env var

CHANGELOG.md

@@ -22,6 +22,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   ([#1656])(https://github.com/open-telemetry/opentelemetry-python/pull/1656)
 - Rename `DefaultSpan` to `NonRecordingSpan`
   ([#1661])(https://github.com/open-telemetry/opentelemetry-python/pull/1661)
+- Fixed distro configuration with `OTEL_TRACES_EXPORTER` env var set to `otlp`
+  ([#1657])(https://github.com/open-telemetry/opentelemetry-python/pull/1657)
 - Moving `Getter`, `Setter` and `TextMapPropagator` out of `opentelemetry.trace.propagation` and
   into `opentelemetry.propagators`
   ([#1662])(https://github.com/open-telemetry/opentelemetry-python/pull/1662)

opentelemetry-distro/src/opentelemetry/distro/__init__.py

@@ -67,7 +67,7 @@ def _get_exporter_names() -> Sequence[str]:
         )
 
     if EXPORTER_OTLP in exporters:
-        exporters.pop(EXPORTER_OTLP)
+        exporters.remove(EXPORTER_OTLP)
         exporters.add(EXPORTER_OTLP_SPAN)
 
     return list(exporters)

opentelemetry-distro/tests/test_configurator.py

@@ -18,13 +18,17 @@
 from unittest.mock import patch
 
 from opentelemetry.distro import (
+    EXPORTER_OTLP,
+    EXPORTER_OTLP_SPAN,
+    _get_exporter_names,
     _get_id_generator,
     _import_id_generator,
     _init_tracing,
 )
 from opentelemetry.environment_variables import (
     OTEL_PYTHON_ID_GENERATOR,
     OTEL_PYTHON_SERVICE_NAME,
+    OTEL_TRACES_EXPORTER,
 )
 from opentelemetry.sdk.resources import Resource
 from opentelemetry.sdk.trace.id_generator import IdGenerator, RandomIdGenerator
@@ -143,3 +147,14 @@ def test_trace_init_custom_id_generator(self, mock_iter_entry_points):
         _init_tracing({}, id_generator)
         provider = self.set_provider_mock.call_args[0][0]
         self.assertIsInstance(provider.id_generator, CustomIdGenerator)
+
+
+class TestExporterNames(TestCase):
+    def test_otlp_exporter_overwrite(self):
+        for exporter in [EXPORTER_OTLP, EXPORTER_OTLP_SPAN]:
+            with patch.dict(environ, {OTEL_TRACES_EXPORTER: exporter}):
+                self.assertEqual(_get_exporter_names(), [EXPORTER_OTLP_SPAN])
+
+    @patch.dict(environ, {OTEL_TRACES_EXPORTER: "jaeger,zipkin"})
+    def test_multiple_exporters(self):
+        self.assertEqual(sorted(_get_exporter_names()), ["jaeger", "zipkin"])