fix(django): avoid empty span name on empty path

CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## Unreleased
 
+### Fixed
+
+- `opentelemetry-instrumentation-django` Fix empty span name when using
+  `path("", ...)` ([#1788](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/1788)
 - Fix falcon instrumentation's usage of Span Status to only set the description if the status code is ERROR.
   ([#1840](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/1840))
 - Instrument all httpx versions >= 0.18. ([#1748](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/1748))

instrumentation/opentelemetry-instrumentation-django/src/opentelemetry/instrumentation/django/middleware/otel_middleware.py

@@ -172,7 +172,7 @@ def _get_span_name(request):
             else:
                 match = resolve(request.path)
 
-            if hasattr(match, "route"):
+            if hasattr(match, "route") and match.route:
                 return f"{request.method} {match.route}"
 
             return request.method

instrumentation/opentelemetry-instrumentation-django/tests/test_middleware.py

@@ -75,8 +75,11 @@
 
 if DJANGO_2_0:
     from django.urls import re_path
+    from django.urls import path
 else:
     from django.conf.urls import url as re_path
+    def path(p, *args, **kwargs):
+      return re_path(r"^%s$" % p, *args, **kwargs)
 
 urlpatterns = [
     re_path(r"^traced/", traced),
@@ -87,6 +90,7 @@
     re_path(r"^excluded_noarg/", excluded_noarg),
     re_path(r"^excluded_noarg2/", excluded_noarg2),
     re_path(r"^span_name/([0-9]{4})/$", route_span_name),
+    path("", traced, name="empty"),
 ]
 _django_instrumentor = DjangoInstrumentor()
 
@@ -205,6 +209,16 @@ def test_not_recording(self):
             self.assertFalse(mock_span.set_attribute.called)
             self.assertFalse(mock_span.set_status.called)
 
+    def test_empty_path(self):
+        Client().get("/")
+
+        spans = self.memory_exporter.get_finished_spans()
+        self.assertEqual(len(spans), 1)
+
+        span = spans[0]
+
+        self.assertEqual(span.name, "empty")
+
     def test_traced_post(self):
         Client().post("/traced/")