MyPy azure-core (#6619)

* MyPy azure-core settings

* MyPy azure-core aiohttp

* Redesign sentinel

sdk/core/azure-core/azure/core/pipeline/transport/aiohttp.py

@@ -31,7 +31,7 @@
 import aiohttp
 
 from azure.core.configuration import ConnectionConfiguration
-from azure.core.exceptions import ServiceRequestError, ServiceResponseError
+from azure.core.exceptions import ServiceRequestError, ServiceResponseError, AzureError
 from azure.core.pipeline import Pipeline
 
 from requests.exceptions import (
@@ -159,7 +159,7 @@ async def send(self, request: HttpRequest, **config: Any) -> Optional[AsyncHttpR
                     config['proxy'] = proxies[protocol]
                     break
 
-        error = None
+        error = None  # type: Optional[AzureError]
         response = None
         config['ssl'] = self._build_ssl_config(
             cert=config.pop('connection_cert', self.connection_config.cert),

sdk/core/azure-core/azure/core/settings.py

@@ -29,18 +29,23 @@
 """
 
 from collections import namedtuple
+from enum import Enum
 import logging
 import os
 import six
 import sys
 
 try:
-    from typing import TYPE_CHECKING
+    from typing import Type, Optional, Dict, Callable, cast, TYPE_CHECKING
 except ImportError:
     TYPE_CHECKING = False
 
 if TYPE_CHECKING:
     from typing import Any, Union
+    try:
+        from azure.core.tracing.ext.opencensus_span import OpenCensusSpan
+    except ImportError:
+        pass
 
 
 from azure.core.tracing import AbstractSpan
@@ -49,8 +54,10 @@
 __all__ = ("settings",)
 
 
-class _Unset(object):
-    pass
+# https://www.python.org/dev/peps/pep-0484/#support-for-singleton-types-in-unions
+class _Unset(Enum):
+    token = 0
+_unset = _Unset.token
 
 
 def convert_bool(value):
@@ -119,7 +126,7 @@ def convert_logging(value):
 
 
 def get_opencensus_span():
-    # type: () -> OpenCensusSpan
+    # type: () -> Optional[Type[AbstractSpan]]
     """Returns the OpenCensusSpan if opencensus is installed else returns None"""
     try:
         from azure.core.tracing.ext.opencensus_span import OpenCensusSpan
@@ -130,16 +137,17 @@ def get_opencensus_span():
 
 
 def get_opencensus_span_if_opencensus_is_imported():
+    # type: () -> Optional[Type[AbstractSpan]]
     if "opencensus" not in sys.modules:
         return None
     return get_opencensus_span()
 
 
-_tracing_implementation_dict = {"opencensus": get_opencensus_span}
+_tracing_implementation_dict = {"opencensus": get_opencensus_span}  # type: Dict[str, Callable[[], Optional[Type[AbstractSpan]]]]
 
 
 def convert_tracing_impl(value):
-    # type: (Union[str, AbstractSpan]) -> AbstractSpan
+    # type: (Union[str, Type[AbstractSpan]]) -> Optional[Type[AbstractSpan]]
     """Convert a string to AbstractSpan
 
     If a AbstractSpan is passed in, it is returned as-is. Otherwise the function
@@ -156,19 +164,21 @@ def convert_tracing_impl(value):
     if value is None:
         return get_opencensus_span_if_opencensus_is_imported()
 
-    wrapper_class = value
-    if isinstance(value, six.string_types):
-        value = value.lower()
-        get_wrapper_class = _tracing_implementation_dict.get(value, lambda: _Unset)
-        wrapper_class = get_wrapper_class()
-        if wrapper_class is _Unset:
-            raise ValueError(
-                "Cannot convert {} to AbstractSpan, valid values are: {}".format(
-                    value, ", ".join(_tracing_implementation_dict)
-                )
+    if not isinstance(value, six.string_types):
+        return value
+
+    value = cast(str, value)  # mypy clarity
+    value = value.lower()
+    get_wrapper_class = _tracing_implementation_dict.get(value, lambda: _unset)
+    wrapper_class = get_wrapper_class()  # type: Union[None, _Unset, Type[AbstractSpan]]
+    if wrapper_class is _unset:
+        raise ValueError(
+            "Cannot convert {} to AbstractSpan, valid values are: {}".format(
+                value, ", ".join(_tracing_implementation_dict)
             )
-
-    return wrapper_class
+        )
+    # type ignored until https://github.com/python/mypy/issues/7279
+    return wrapper_class  # type: ignore
 
 
 class PrioritizedSetting(object):