overload tracing decorator to preserve type info (#9994)

* overload tracing decorator to preserve type info

* use pass instead of ellipsis for py2

* mypy,pylint

sdk/core/azure-core/azure/core/tracing/decorator.py

@@ -27,6 +27,8 @@
 
 import functools
 
+from typing import overload
+
 from .common import change_context, get_function_and_class_name
 from ..settings import settings
 
@@ -36,49 +38,61 @@
     TYPE_CHECKING = False
 
 if TYPE_CHECKING:
-    from typing import Callable, Dict, Optional, Any, cast
+    from typing import Callable, Dict, Optional, Any, TypeVar
+
+    T = TypeVar("T")
+
+
+@overload
+def distributed_trace(__func):
+    # type: (Callable[..., T]) -> Callable[..., T]
+    pass
 
 
-def distributed_trace(_func=None, name_of_span=None, **kwargs):
-    # type: (Callable, Optional[str], Optional[Dict[str, Any]]) -> Callable
+@overload
+def distributed_trace(**kwargs):  # pylint:disable=function-redefined,unused-argument
+    # type: (**Any) -> Callable[[Callable[..., T]], Callable[..., T]]
+    pass
+
+
+def distributed_trace(  # pylint:disable=function-redefined
+    __func=None,  # type: Callable[..., T]
+    **kwargs  # type: Any
+):
     """Decorator to apply to function to get traced automatically.
 
     Span will use the func name or "name_of_span".
 
     :param callable func: A function to decorate
     :param str name_of_span: The span name to replace func name if necessary
     """
-    tracing_attributes = kwargs.get('tracing_attributes')
-    # https://github.com/python/mypy/issues/2608
-    if _func is None:
-        return functools.partial(
-            distributed_trace,
-            name_of_span=name_of_span,
-            tracing_attributes=tracing_attributes,
-        )
-    func = _func  # mypy is happy now
-
-    not_none_tracing_attributes = tracing_attributes if tracing_attributes else {}
-
-    @functools.wraps(func)
-    def wrapper_use_tracer(*args, **kwargs):
-        # type: (Any, Any) -> Any
-        merge_span = kwargs.pop("merge_span", False)
-        passed_in_parent = kwargs.pop("parent_span", None)
-
-        span_impl_type = settings.tracing_implementation()
-        if span_impl_type is None:
-            return func(*args, **kwargs)
-
-        # Merge span is parameter is set, but only if no explicit parent are passed
-        if merge_span and not passed_in_parent:
-            return func(*args, **kwargs)
-
-        with change_context(passed_in_parent):
-            name = name_of_span or get_function_and_class_name(func, *args)
-            with span_impl_type(name=name) as span:
-                for key, value in not_none_tracing_attributes.items():
-                    span.add_attribute(key, value)
+    name_of_span = kwargs.pop("name_of_span", None)
+    tracing_attributes = kwargs.pop("tracing_attributes", {})
+
+    def decorator(func):
+        # type: (Callable[..., T]) -> Callable[..., T]
+
+        @functools.wraps(func)
+        def wrapper_use_tracer(*args, **kwargs):
+            # type: (*Any, **Any) -> T
+            merge_span = kwargs.pop("merge_span", False)
+            passed_in_parent = kwargs.pop("parent_span", None)
+
+            span_impl_type = settings.tracing_implementation()
+            if span_impl_type is None:
+                return func(*args, **kwargs)
+
+            # Merge span is parameter is set, but only if no explicit parent are passed
+            if merge_span and not passed_in_parent:
                 return func(*args, **kwargs)
 
-    return wrapper_use_tracer
+            with change_context(passed_in_parent):
+                name = name_of_span or get_function_and_class_name(func, *args)
+                with span_impl_type(name=name) as span:
+                    for key, value in tracing_attributes.items():
+                        span.add_attribute(key, value)
+                    return func(*args, **kwargs)
+
+        return wrapper_use_tracer
+
+    return decorator if __func is None else decorator(__func)

sdk/core/azure-core/azure/core/tracing/decorator_async.py

@@ -27,57 +27,64 @@
 
 import functools
 
+from typing import Awaitable, Callable, Dict, Optional, Any, TypeVar, overload
+
 from .common import change_context, get_function_and_class_name
 from ..settings import settings
 
-try:
-    from typing import TYPE_CHECKING
-except ImportError:
-    TYPE_CHECKING = False
 
-if TYPE_CHECKING:
-    from typing import Callable, Dict, Optional, Any
+T = TypeVar("T")
+
+
+@overload
+def distributed_trace_async(
+    __func: Callable[..., Awaitable[T]]
+) -> Callable[..., Awaitable[T]]:
+    pass
 
 
-def distributed_trace_async(_func=None, name_of_span=None, *, tracing_attributes=None):
-    # type: (Callable, Optional[str], Optional[Dict[str, Any]]) -> Callable
-    """Decorator to apply to async function to get traced automatically.
+@overload
+def distributed_trace_async(  # pylint:disable=function-redefined
+    **kwargs: Any  # pylint:disable=unused-argument
+) -> Callable[[Callable[..., Awaitable[T]]], Callable[..., Awaitable[T]]]:
+    pass
+
+
+def distributed_trace_async(  # pylint:disable=function-redefined
+    __func: Callable[..., Awaitable[T]] = None, **kwargs: Any
+):
+    """Decorator to apply to function to get traced automatically.
 
     Span will use the func name or "name_of_span".
 
     :param callable func: A function to decorate
     :param str name_of_span: The span name to replace func name if necessary
     """
-    # https://github.com/python/mypy/issues/2608
-    if _func is None:
-        return functools.partial(
-            distributed_trace_async,
-            name_of_span=name_of_span,
-            tracing_attributes=tracing_attributes,
-        )
-    func = _func  # mypy is happy now
-
-    not_none_tracing_attributes = tracing_attributes if tracing_attributes else {}
-
-    @functools.wraps(func)
-    async def wrapper_use_tracer(*args, **kwargs):
-        # type: (Any, Any) -> Any
-        merge_span = kwargs.pop("merge_span", False)
-        passed_in_parent = kwargs.pop("parent_span", None)
-
-        span_impl_type = settings.tracing_implementation()
-        if span_impl_type is None:
-            return await func(*args, **kwargs)
-
-        # Merge span is parameter is set, but only if no explicit parent are passed
-        if merge_span and not passed_in_parent:
-            return await func(*args, **kwargs)
-
-        with change_context(passed_in_parent):
-            name = name_of_span or get_function_and_class_name(func, *args)
-            with span_impl_type(name=name) as span:
-                for key, value in not_none_tracing_attributes.items():
-                    span.add_attribute(key, value)
+    name_of_span = kwargs.pop("name_of_span", None)
+    tracing_attributes = kwargs.pop("tracing_attributes", {})
+
+    def decorator(func: Callable[..., Awaitable[T]]) -> Callable[..., Awaitable[T]]:
+        @functools.wraps(func)
+        async def wrapper_use_tracer(*args, **kwargs):
+            # type: (*Any, **Any) -> T
+            merge_span = kwargs.pop("merge_span", False)
+            passed_in_parent = kwargs.pop("parent_span", None)
+
+            span_impl_type = settings.tracing_implementation()
+            if span_impl_type is None:
+                return await func(*args, **kwargs)
+
+            # Merge span is parameter is set, but only if no explicit parent are passed
+            if merge_span and not passed_in_parent:
                 return await func(*args, **kwargs)
 
-    return wrapper_use_tracer
+            with change_context(passed_in_parent):
+                name = name_of_span or get_function_and_class_name(func, *args)
+                with span_impl_type(name=name) as span:
+                    for key, value in tracing_attributes.items():
+                        span.add_attribute(key, value)
+                    return await func(*args, **kwargs)
+
+        return wrapper_use_tracer
+
+    return decorator if __func is None else decorator(__func)