Fix auto-instrumentation dependency conflict detection

Author: owais

CHANGELOG.md

@@ -6,6 +6,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased](https://github.com/open-telemetry/opentelemetry-python/compare/v1.3.0-0.22b0...HEAD)
 
+- `opentelemetry-instrumentation` Fixed cases where trying to use an instrumentation package without the
+  target library was crashing auto instrumentation agent.
+  ([#530](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/530))
+
 ## [0.22b0](https://github.com/open-telemetry/opentelemetry-python/releases/tag/v1.3.0-0.22b0) - 2021-06-01
 
 ### Changed

opentelemetry-instrumentation/src/opentelemetry/instrumentation/dependencies.py

@@ -25,20 +25,27 @@ def __str__(self):
 def get_dist_dependency_conflicts(
     dist: Distribution,
 ) -> Optional[DependencyConflict]:
-    deps = [
-        dep
-        for dep in dist.requires(("instruments",))
-        if dep not in dist.requires()
-    ]
-    return get_dependency_conflicts(deps)
+    main_deps = dist.requires()
+    instrumentation_deps = []
+    for dep in dist.requires(("instruments",)):
+        if dep not in main_deps:
+            # we set marker to none so string representation of the dependency looks like
+            #    requests ~= 1.0
+            # instead of
+            #    requests ~= 1.0; extra = "instruments"
+            # which does not work with `get_distribution()`
+            dep.marker = None
+            instrumentation_deps.append(str(dep))
+
+    return get_dependency_conflicts(instrumentation_deps)
 
 
 def get_dependency_conflicts(
     deps: Collection[str],
 ) -> Optional[DependencyConflict]:
     for dep in deps:
         try:
-            get_distribution(str(dep))
+            get_distribution(dep)
         except VersionConflict as exc:
             return DependencyConflict(dep, exc.dist)
         except DistributionNotFound:

opentelemetry-instrumentation/tests/test_dependencies.py

@@ -14,11 +14,13 @@
 
 # pylint: disable=protected-access
 
+import pkg_resources
 import pytest
 
 from opentelemetry.instrumentation.dependencies import (
     DependencyConflict,
     get_dependency_conflicts,
+    get_dist_dependency_conflicts,
 )
 from opentelemetry.test.test_base import TestBase
 
@@ -37,7 +39,6 @@ def test_get_dependency_conflicts_not_installed(self):
         conflict = get_dependency_conflicts(["this-package-does-not-exist"])
         self.assertTrue(conflict is not None)
         self.assertTrue(isinstance(conflict, DependencyConflict))
-        print(conflict)
         self.assertEqual(
             str(conflict),
             'DependencyConflict: requested: "this-package-does-not-exist" but found: "None"',
@@ -47,10 +48,32 @@ def test_get_dependency_conflicts_mismatched_version(self):
         conflict = get_dependency_conflicts(["pytest == 5000"])
         self.assertTrue(conflict is not None)
         self.assertTrue(isinstance(conflict, DependencyConflict))
-        print(conflict)
         self.assertEqual(
             str(conflict),
             'DependencyConflict: requested: "pytest == 5000" but found: "pytest {0}"'.format(
                 pytest.__version__
             ),
         )
+
+    def test_get_dist_dependency_conflicts(self):
+        def mock_requires(extras=()):
+            if "instruments" in extras:
+                return [
+                    pkg_resources.Requirement(
+                        'test-pkg ~= 1.0; extra == "instruments"'
+                    )
+                ]
+            return []
+
+        dist = pkg_resources.Distribution(
+            project_name="test-instrumentation", version="1.0"
+        )
+        dist.requires = mock_requires
+
+        conflict = get_dist_dependency_conflicts(dist)
+        self.assertTrue(conflict is not None)
+        self.assertTrue(isinstance(conflict, DependencyConflict))
+        self.assertEqual(
+            str(conflict),
+            'DependencyConflict: requested: "test-pkg~=1.0" but found: "None"',
+        )