Fix some "errors" found by mypy.

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

@@ -138,19 +138,14 @@ async def main():
         asyncio.run(main())
 """
 
-import typing
-
 from .base_context import BaseRuntimeContext
 
 __all__ = ["Context"]
 
-
-Context = None  # type: typing.Optional[BaseRuntimeContext]
-
 try:
     from .async_context import AsyncRuntimeContext
 
-    Context = AsyncRuntimeContext()
+    Context = AsyncRuntimeContext()  # type: BaseRuntimeContext
 except ImportError:
     from .thread_local_context import ThreadLocalRuntimeContext
 

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

@@ -142,7 +142,7 @@ class SpanKind(enum.Enum):
 class Span:
     """A span represents a single operation within a trace."""
 
-    def start(self, start_time: int = None) -> None:
+    def start(self, start_time: typing.Optional[int] = None) -> None:
         """Sets the current time as the span's start time.
 
         Each span represents a single operation. The span's start time is the

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

@@ -35,7 +35,7 @@ class B3Format(HTTPTextFormat):
     def extract(cls, get_from_carrier, carrier):
         trace_id = format_trace_id(trace.INVALID_TRACE_ID)
         span_id = format_span_id(trace.INVALID_SPAN_ID)
-        sampled = 0
+        sampled = "0"
         flags = None
 
         single_header = _extract_first_element(
@@ -95,8 +95,8 @@ def extract(cls, get_from_carrier, carrier):
             # trace an span ids are encoded in hex, so must be converted
             trace_id=int(trace_id, 16),
             span_id=int(span_id, 16),
-            trace_options=options,
-            trace_state={},
+            trace_options=trace.TraceOptions(options),
+            trace_state=trace.TraceState(),
         )
 
     @classmethod
@@ -111,17 +111,20 @@ def inject(cls, context, set_in_carrier, carrier):
         set_in_carrier(carrier, cls.SAMPLED_KEY, "1" if sampled else "0")
 
 
-def format_trace_id(trace_id: int):
+def format_trace_id(trace_id: int) -> str:
     """Format the trace id according to b3 specification."""
     return format(trace_id, "032x")
 
 
-def format_span_id(span_id: int):
+def format_span_id(span_id: int) -> str:
     """Format the span id according to b3 specification."""
     return format(span_id, "016x")
 
 
-def _extract_first_element(list_object: list) -> typing.Optional[object]:
-    if list_object:
-        return list_object[0]
-    return None
+_T = typing.TypeVar("_T")
+
+
+def _extract_first_element(items: typing.Iterable[_T]) -> typing.Optional[_T]:
+    if items is None:
+        return None
+    return next(iter(items), None)

opentelemetry-sdk/src/opentelemetry/sdk/metrics/__init__.py

@@ -27,12 +27,12 @@ def __init__(
         enabled: bool,
         monotonic: bool,
     ):
-        self.data = 0
+        self.data = value_type()
         self.value_type = value_type
         self.enabled = enabled
         self.monotonic = monotonic
 
-    def _validate_update(self, value: metrics_api.ValueT):
+    def _validate_update(self, value: metrics_api.ValueT) -> bool:
         if not self.enabled:
             return False
         if not isinstance(value, self.value_type):
@@ -232,7 +232,8 @@ def create_metric(
         monotonic: bool = False,
     ) -> metrics_api.MetricT:
         """See `opentelemetry.metrics.Meter.create_metric`."""
-        return metric_type(
+        # Ignore type b/c of mypy bug in addition to missing annotations
+        return metric_type(  # type: ignore
             name,
             description,
             unit,

opentelemetry-sdk/src/opentelemetry/sdk/trace/__init__.py

@@ -73,10 +73,10 @@ class MultiSpanProcessor(SpanProcessor):
     def __init__(self):
         # use a tuple to avoid race conditions when adding a new span and
         # iterating through it on "on_start" and "on_end".
-        self._span_processors = ()
+        self._span_processors = ()  # type: typing.Tuple[SpanProcessor, ...]
         self._lock = threading.Lock()
 
-    def add_span_processor(self, span_processor: SpanProcessor):
+    def add_span_processor(self, span_processor: SpanProcessor) -> None:
         """Adds a SpanProcessor to the list handled by this instance."""
         with self._lock:
             self._span_processors = self._span_processors + (span_processor,)
@@ -122,11 +122,11 @@ class Span(trace_api.Span):
     def __init__(
         self,
         name: str,
-        context: "trace_api.SpanContext",
+        context: trace_api.SpanContext,
         parent: trace_api.ParentSpan = None,
-        sampler=None,  # TODO
-        trace_config=None,  # TODO
-        resource=None,  # TODO
+        sampler: None = None,  # TODO
+        trace_config: None = None,  # TODO
+        resource: None = None,  # TODO
         attributes: types.Attributes = None,  # TODO
         events: typing.Sequence[trace_api.Event] = None,  # TODO
         links: typing.Sequence[trace_api.Link] = None,  # TODO
@@ -140,9 +140,6 @@ def __init__(
         self.sampler = sampler
         self.trace_config = trace_config
         self.resource = resource
-        self.attributes = attributes
-        self.events = events
-        self.links = links
         self.kind = kind
 
         self.span_processor = span_processor
@@ -165,8 +162,8 @@ def __init__(
         else:
             self.links = BoundedList.from_seq(MAX_NUM_LINKS, links)
 
-        self.end_time = None
-        self.start_time = None
+        self.end_time = None  # type: typing.Optional[int]
+        self.start_time = None  # type: typing.Optional[int]
 
     def __repr__(self):
         return '{}(name="{}", context={})'.format(
@@ -203,9 +200,13 @@ def set_attribute(self, key: str, value: types.AttributeValue) -> None:
     def add_event(
         self, name: str, attributes: types.Attributes = None
     ) -> None:
-        if attributes is None:
-            attributes = Span.empty_attributes
-        self.add_lazy_event(trace_api.Event(name, time_ns(), attributes))
+        self.add_lazy_event(
+            trace_api.Event(
+                name,
+                time_ns(),
+                Span.empty_attributes if attributes is None else attributes,
+            )
+        )
 
     def add_lazy_event(self, event: trace_api.Event) -> None:
         with self._lock:
@@ -226,7 +227,9 @@ def add_link(
         attributes: types.Attributes = None,
     ) -> None:
         if attributes is None:
-            attributes = Span.empty_attributes
+            attributes = (
+                Span.empty_attributes
+            )  # TODO: empty_attributes is not a Dict. Use Mapping?
         self.add_lazy_link(trace_api.Link(link_target_context, attributes))
 
     def add_lazy_link(self, link: "trace_api.Link") -> None:
@@ -242,7 +245,7 @@ def add_lazy_link(self, link: "trace_api.Link") -> None:
             return
         self.links.append(link)
 
-    def start(self, start_time: int = None):
+    def start(self, start_time: typing.Optional[int] = None) -> None:
         with self._lock:
             if not self.is_recording_events():
                 return
@@ -256,7 +259,7 @@ def start(self, start_time: int = None):
             return
         self.span_processor.on_start(self)
 
-    def end(self, end_time: int = None):
+    def end(self, end_time: int = None) -> None:
         with self._lock:
             if not self.is_recording_events():
                 return
@@ -283,7 +286,7 @@ def is_recording_events(self) -> bool:
         return True
 
 
-def generate_span_id():
+def generate_span_id() -> int:
     """Get a new random span ID.
 
     Returns:
@@ -292,7 +295,7 @@ def generate_span_id():
     return random.getrandbits(64)
 
 
-def generate_trace_id():
+def generate_trace_id() -> int:
     """Get a new random trace ID.
 
     Returns:
@@ -325,7 +328,7 @@ def start_span(
         name: str,
         parent: trace_api.ParentSpan = trace_api.Tracer.CURRENT_SPAN,
         kind: trace_api.SpanKind = trace_api.SpanKind.INTERNAL,
-    ) -> typing.Iterator["Span"]:
+    ) -> typing.Iterator[trace_api.Span]:
         """See `opentelemetry.trace.Tracer.start_span`."""
 
         span = self.create_span(name, parent, kind)
@@ -368,8 +371,8 @@ def create_span(
 
     @contextmanager
     def use_span(
-        self, span: Span, end_on_exit: bool = False
-    ) -> typing.Iterator[Span]:
+        self, span: trace_api.Span, end_on_exit: bool = False
+    ) -> typing.Iterator[trace_api.Span]:
         """See `opentelemetry.trace.Tracer.use_span`."""
         try:
             span_snapshot = self._current_span_slot.get()

opentelemetry-sdk/src/opentelemetry/sdk/trace/export/__init__.py

@@ -118,7 +118,9 @@ def __init__(
             )
 
         self.span_exporter = span_exporter
-        self.queue = collections.deque([], max_queue_size)
+        self.queue = collections.deque(
+            [], max_queue_size
+        )  # type: typing.Deque[Span]
         self.worker_thread = threading.Thread(target=self.worker, daemon=True)
         self.condition = threading.Condition(threading.Lock())
         self.schedule_delay_millis = schedule_delay_millis
@@ -128,7 +130,9 @@ def __init__(
         # flag that indicates that spans are being dropped
         self._spans_dropped = False
         # precallocated list to send spans to exporter
-        self.spans_list = [None] * self.max_export_batch_size
+        self.spans_list = [
+            None
+        ] * self.max_export_batch_size  # type: typing.List[typing.Optional[Span]]
         self.worker_thread.start()
 
     def on_start(self, span: Span) -> None:
@@ -172,7 +176,7 @@ def worker(self):
         # be sure that all spans are sent
         self._flush()
 
-    def export(self) -> bool:
+    def export(self) -> None:
         """Exports at most max_export_batch_size spans."""
         idx = 0
 
@@ -184,7 +188,8 @@ def export(self) -> bool:
         suppress_instrumentation = Context.suppress_instrumentation
         try:
             Context.suppress_instrumentation = True
-            self.span_exporter.export(self.spans_list[:idx])
+            # Ignore type b/c the Optional[None]+slicing is too "clever" for mypy
+            self.span_exporter.export(self.spans_list[:idx])  # type: ignore
         # pylint: disable=broad-except
         except Exception:
             logger.exception("Exception while exporting data.")

opentelemetry-sdk/src/opentelemetry/sdk/util.py

@@ -41,7 +41,7 @@ class BoundedList(Sequence):
 
     def __init__(self, maxlen):
         self.dropped = 0
-        self._dq = deque(maxlen=maxlen)
+        self._dq = deque(maxlen=maxlen)  # type: deque
         self._lock = threading.Lock()
 
     def __repr__(self):
@@ -97,8 +97,8 @@ def __init__(self, maxlen):
             raise ValueError
         self.maxlen = maxlen
         self.dropped = 0
-        self._dict = OrderedDict()
-        self._lock = threading.Lock()
+        self._dict = OrderedDict()  # type: OrderedDict
+        self._lock = threading.Lock()  # type: threading.Lock
 
     def __repr__(self):
         return "{}({}, maxlen={})".format(