converted textmap propagator getter to a class and added keys method

exporter/opentelemetry-exporter-datadog/src/opentelemetry/exporter/datadog/propagator.py

@@ -39,24 +39,24 @@ class DatadogFormat(TextMapPropagator):
 
     def extract(
         self,
-        get_from_carrier: Getter[TextMapPropagatorT],
+        get_from_carrier: Getter,
         carrier: TextMapPropagatorT,
         context: typing.Optional[Context] = None,
     ) -> Context:
         trace_id = extract_first_element(
-            get_from_carrier(carrier, self.TRACE_ID_KEY)
+            get_from_carrier.get(carrier, self.TRACE_ID_KEY)
         )
 
         span_id = extract_first_element(
-            get_from_carrier(carrier, self.PARENT_ID_KEY)
+            get_from_carrier.get(carrier, self.PARENT_ID_KEY)
         )
 
         sampled = extract_first_element(
-            get_from_carrier(carrier, self.SAMPLING_PRIORITY_KEY)
+            get_from_carrier.get(carrier, self.SAMPLING_PRIORITY_KEY)
         )
 
         origin = extract_first_element(
-            get_from_carrier(carrier, self.ORIGIN_KEY)
+            get_from_carrier.get(carrier, self.ORIGIN_KEY)
         )
 
         trace_flags = trace.TraceFlags()

exporter/opentelemetry-exporter-datadog/tests/test_datadog_format.py

@@ -22,9 +22,18 @@
 FORMAT = propagator.DatadogFormat()
 
 
-def get_as_list(dict_object, key):
-    value = dict_object.get(key)
-    return [value] if value is not None else []
+class Getter:
+    @staticmethod
+    def get(dict_object, key):
+        value = dict_object.get(key)
+        return [value] if value is not None else []
+
+    @staticmethod
+    def keys(dict_object):
+        return dict_object.keys()
+
+
+get_as_list = Getter()
 
 
 class TestDatadogFormat(unittest.TestCase):

opentelemetry-api/src/opentelemetry/baggage/propagation/__init__.py

@@ -29,7 +29,7 @@ class BaggagePropagator(textmap.TextMapPropagator):
 
     def extract(
         self,
-        get_from_carrier: textmap.Getter[textmap.TextMapPropagatorT],
+        get_from_carrier: textmap.Getter,
         carrier: textmap.TextMapPropagatorT,
         context: typing.Optional[Context] = None,
     ) -> Context:
@@ -43,7 +43,7 @@ def extract(
             context = get_current()
 
         header = _extract_first_element(
-            get_from_carrier(carrier, self._BAGGAGE_HEADER_NAME)
+            get_from_carrier.get(carrier, self._BAGGAGE_HEADER_NAME)
         )
 
         if not header or len(header) > self.MAX_HEADER_LENGTH:

opentelemetry-api/src/opentelemetry/propagators/__init__.py

@@ -82,16 +82,16 @@ def example_route():
 
 
 def extract(
-    get_from_carrier: textmap.Getter[textmap.TextMapPropagatorT],
+    get_from_carrier: textmap.Getter,
     carrier: textmap.TextMapPropagatorT,
     context: typing.Optional[Context] = None,
 ) -> Context:
     """ Uses the configured propagator to extract a Context from the carrier.
 
     Args:
-        get_from_carrier: a function that can retrieve zero
-            or more values from the carrier. In the case that
-            the value does not exist, return an empty list.
+        get_from_carrier: an object which contains a get function that can retrieve zero
+            or more values from the carrier and a keys function that can get all the keys
+            from carrier.
         carrier: and object which contains values that are
             used to construct a Context. This object
             must be paired with an appropriate get_from_carrier

opentelemetry-api/src/opentelemetry/propagators/composite.py

@@ -35,7 +35,7 @@ def __init__(
 
     def extract(
         self,
-        get_from_carrier: textmap.Getter[textmap.TextMapPropagatorT],
+        get_from_carrier: textmap.Getter,
         carrier: textmap.TextMapPropagatorT,
         context: typing.Optional[Context] = None,
     ) -> Context:

opentelemetry-api/src/opentelemetry/trace/propagation/textmap.py

@@ -20,7 +20,44 @@
 TextMapPropagatorT = typing.TypeVar("TextMapPropagatorT")
 
 Setter = typing.Callable[[TextMapPropagatorT, str, str], None]
-Getter = typing.Callable[[TextMapPropagatorT, str], typing.List[str]]
+
+
+class Getter(abc.ABC):
+    """This class provides an interface that enables extracting propagated
+    fields from a carrier
+
+    """
+
+    @abc.abstractmethod
+    @staticmethod
+    def get(carrier: TextMapPropagatorT, key: str) -> typing.List[str]:
+        """Function that can retrieve zero
+        or more values from the carrier. In the case that
+        the value does not exist, returns an empty list.
+
+        Args:
+            carrier: and object which contains values that are
+                used to construct a Context. This object
+                must be paired with an appropriate get_from_carrier
+                which understands how to extract a value from it.
+            key: key of a field in carrier.
+        Returns:
+            first value of the propagation key or an empty list if the key doesn't exist.
+        """
+
+    @abc.abstractmethod
+    @staticmethod
+    def keys(carrier: TextMapPropagatorT) -> typing.List[str]:
+        """Function that can retrieve all the keys in a carrier object.
+
+        Args:
+            carrier: and object which contains values that are
+                used to construct a Context. This object
+                must be paired with an appropriate get_from_carrier
+                which understands how to extract a value from it.
+        Returns:
+            list of keys from the carrier.
+        """
 
 
 class TextMapPropagator(abc.ABC):
@@ -35,7 +72,7 @@ class TextMapPropagator(abc.ABC):
     @abc.abstractmethod
     def extract(
         self,
-        get_from_carrier: Getter[TextMapPropagatorT],
+        get_from_carrier: Getter,
         carrier: TextMapPropagatorT,
         context: typing.Optional[Context] = None,
     ) -> Context:

opentelemetry-api/src/opentelemetry/trace/propagation/tracecontext.py

@@ -60,15 +60,15 @@ class TraceContextTextMapPropagator(textmap.TextMapPropagator):
 
     def extract(
         self,
-        get_from_carrier: textmap.Getter[textmap.TextMapPropagatorT],
+        get_from_carrier: textmap.Getter,
         carrier: textmap.TextMapPropagatorT,
         context: typing.Optional[Context] = None,
     ) -> Context:
         """Extracts SpanContext from the carrier.
 
         See `opentelemetry.trace.propagation.textmap.TextMapPropagator.extract`
         """
-        header = get_from_carrier(carrier, self._TRACEPARENT_HEADER_NAME)
+        header = get_from_carrier.get(carrier, self._TRACEPARENT_HEADER_NAME)
 
         if not header:
             return trace.set_span_in_context(trace.INVALID_SPAN, context)
@@ -91,7 +91,7 @@ def extract(
         if version == "ff":
             return trace.set_span_in_context(trace.INVALID_SPAN, context)
 
-        tracestate_headers = get_from_carrier(
+        tracestate_headers = get_from_carrier.get(
             carrier, self._TRACESTATE_HEADER_NAME
         )
         tracestate = _parse_tracestate(tracestate_headers)

opentelemetry-api/tests/baggage/test_baggage_propagation.py

@@ -20,10 +20,17 @@
 from opentelemetry.context import get_current
 
 
-def get_as_list(
-    dict_object: typing.Dict[str, typing.List[str]], key: str
-) -> typing.List[str]:
-    return dict_object.get(key, [])
+class Getter:
+    @staticmethod
+    def get(dict_object, key):
+        return dict_object.get(key, [])
+
+    @staticmethod
+    def keys(dict_object):
+        return dict_object.keys()
+
+
+get_as_list = Getter()
 
 
 class TestBaggagePropagation(unittest.TestCase):

opentelemetry-api/tests/propagators/test_global_httptextformat.py

@@ -20,11 +20,18 @@
 from opentelemetry.trace import get_current_span, set_span_in_context
 
 
-def get_as_list(
-    dict_object: typing.Dict[str, typing.List[str]], key: str
-) -> typing.List[str]:
-    value = dict_object.get(key)
-    return value if value is not None else []
+class Getter:
+    @staticmethod
+    def get(dict_object, key):
+        value = dict_object.get(key)
+        return value if value is not None else []
+
+    @staticmethod
+    def keys(dict_object):
+        return dict_object.keys()
+
+
+get_as_list = Getter()
 
 
 class TestDefaultGlobalPropagator(unittest.TestCase):

opentelemetry-api/tests/trace/propagation/test_tracecontexthttptextformat.py

@@ -21,11 +21,18 @@
 FORMAT = tracecontext.TraceContextTextMapPropagator()
 
 
-def get_as_list(
-    dict_object: typing.Dict[str, typing.List[str]], key: str
-) -> typing.List[str]:
-    value = dict_object.get(key)
-    return value if value is not None else []
+class Getter:
+    @staticmethod
+    def get(dict_object, key):
+        value = dict_object.get(key)
+        return value if value is not None else []
+
+    @staticmethod
+    def keys(dict_object):
+        return dict_object.keys()
+
+
+get_as_list = Getter()
 
 
 class TestTraceContextFormat(unittest.TestCase):

opentelemetry-sdk/src/opentelemetry/sdk/trace/propagation/b3_format.py

@@ -43,7 +43,7 @@ class B3Format(TextMapPropagator):
 
     def extract(
         self,
-        get_from_carrier: Getter[TextMapPropagatorT],
+        get_from_carrier: Getter,
         carrier: TextMapPropagatorT,
         context: typing.Optional[Context] = None,
     ) -> Context:
@@ -53,7 +53,7 @@ def extract(
         flags = None
 
         single_header = _extract_first_element(
-            get_from_carrier(carrier, self.SINGLE_HEADER_KEY)
+            get_from_carrier.get(carrier, self.SINGLE_HEADER_KEY)
         )
         if single_header:
             # The b3 spec calls for the sampling state to be
@@ -75,25 +75,25 @@ def extract(
         else:
             trace_id = (
                 _extract_first_element(
-                    get_from_carrier(carrier, self.TRACE_ID_KEY)
+                    get_from_carrier.get(carrier, self.TRACE_ID_KEY)
                 )
                 or trace_id
             )
             span_id = (
                 _extract_first_element(
-                    get_from_carrier(carrier, self.SPAN_ID_KEY)
+                    get_from_carrier.get(carrier, self.SPAN_ID_KEY)
                 )
                 or span_id
             )
             sampled = (
                 _extract_first_element(
-                    get_from_carrier(carrier, self.SAMPLED_KEY)
+                    get_from_carrier.get(carrier, self.SAMPLED_KEY)
                 )
                 or sampled
             )
             flags = (
                 _extract_first_element(
-                    get_from_carrier(carrier, self.FLAGS_KEY)
+                    get_from_carrier.get(carrier, self.FLAGS_KEY)
                 )
                 or flags
             )

opentelemetry-sdk/tests/trace/propagation/test_b3_format.py

@@ -23,9 +23,18 @@
 FORMAT = b3_format.B3Format()
 
 
-def get_as_list(dict_object, key):
-    value = dict_object.get(key)
-    return [value] if value is not None else []
+class Getter:
+    @staticmethod
+    def get(dict_object, key):
+        value = dict_object.get(key)
+        return [value] if value is not None else []
+
+    @staticmethod
+    def keys(dict_object):
+        return dict_object.keys()
+
+
+get_as_list = Getter()
 
 
 def get_child_parent_new_carrier(old_carrier):
@@ -321,11 +330,8 @@ def test_inject_empty_context():
     def test_default_span():
         """Make sure propagator does not crash when working with DefaultSpan"""
 
-        def getter(carrier, key):
-            return carrier.get(key, None)
-
         def setter(carrier, key, value):
             carrier[key] = value
 
-        ctx = FORMAT.extract(getter, {})
+        ctx = FORMAT.extract(get_as_list, {})
         FORMAT.inject(setter, {}, ctx)

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

@@ -33,7 +33,7 @@ class NOOPTextMapPropagator(TextMapPropagator):
 
     def extract(
         self,
-        get_from_carrier: Getter[TextMapPropagatorT],
+        get_from_carrier: Getter,
         carrier: TextMapPropagatorT,
         context: typing.Optional[Context] = None,
     ) -> Context:
@@ -56,12 +56,12 @@ class MockTextMapPropagator(TextMapPropagator):
 
     def extract(
         self,
-        get_from_carrier: Getter[TextMapPropagatorT],
+        get_from_carrier: Getter,
         carrier: TextMapPropagatorT,
         context: typing.Optional[Context] = None,
     ) -> Context:
-        trace_id_list = get_from_carrier(carrier, self.TRACE_ID_KEY)
-        span_id_list = get_from_carrier(carrier, self.SPAN_ID_KEY)
+        trace_id_list = get_from_carrier.get(carrier, self.TRACE_ID_KEY)
+        span_id_list = get_from_carrier.get(carrier, self.SPAN_ID_KEY)
 
         if not trace_id_list or not span_id_list:
             return trace.set_span_in_context(trace.INVALID_SPAN)