Fix ASGIGetter keys to fetch from actual carrier headers (#1435)

Author: hasier

Diff for: CHANGELOG.md

@@ -21,6 +21,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   ([#1507](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/1507))
 - Fix pymongo to collect the property DB_MONGODB_COLLECTION
   ([#1555](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/1555))
+- `opentelemetry-instrumentation-asgi` Fix keys() in class ASGIGetter to correctly fetch values from carrier headers.
+  ([#1435](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/1435))
+
 
 ## Version 1.15.0/0.36b0 (2022-12-10)
 

Diff for: instrumentation/opentelemetry-instrumentation-asgi/src/opentelemetry/instrumentation/asgi/__init__.py

@@ -260,7 +260,8 @@ def get(
         return decoded
 
     def keys(self, carrier: dict) -> typing.List[str]:
-        return [_key.decode("utf8") for (_key, _value) in carrier]
+        headers = carrier.get("headers") or []
+        return [_key.decode("utf8") for (_key, _value) in headers]
 
 
 asgi_getter = ASGIGetter()

Diff for: instrumentation/opentelemetry-instrumentation-asgi/tests/test_getter.py

@@ -18,12 +18,18 @@
 
 
 class TestASGIGetter(TestCase):
-    def test_get_none(self):
+    def test_get_none_empty_carrier(self):
         getter = ASGIGetter()
         carrier = {}
         val = getter.get(carrier, "test")
         self.assertIsNone(val)
 
+    def test_get_none_empty_headers(self):
+        getter = ASGIGetter()
+        carrier = {"headers": []}
+        val = getter.get(carrier, "test")
+        self.assertIsNone(val)
+
     def test_get_(self):
         getter = ASGIGetter()
         carrier = {"headers": [(b"test-key", b"val")]}
@@ -44,7 +50,22 @@ def test_get_(self):
             "Should be case insensitive",
         )
 
-    def test_keys(self):
+    def test_keys_empty_carrier(self):
         getter = ASGIGetter()
         keys = getter.keys({})
         self.assertEqual(keys, [])
+
+    def test_keys_empty_headers(self):
+        getter = ASGIGetter()
+        keys = getter.keys({"headers": []})
+        self.assertEqual(keys, [])
+
+    def test_keys(self):
+        getter = ASGIGetter()
+        carrier = {"headers": [(b"test-key", b"val")]}
+        expected_val = ["test-key"]
+        self.assertEqual(
+            getter.keys(carrier),
+            expected_val,
+            "Should be equal",
+        )