Introduce to_dict

Introduce `to_dict` to the objects included in the existing
JSON serialization process for `ReadableSpan`, `MetricsData`,
`LogRecord`, and `Resource` objects. This includes adding
`to_dict` to objects that are included within the serialized
data structures of these objects. In places where `repr()`
serialization was used, it has been replaced by a
JSON-compatible serialization instead. Inconsistencies between
null and empty string values were preserved, but in cases
where attributes are optional, an empty dictionary is provided
as well to be more consistent with cases where attributes are
not optional and an empty dictionary represents no attributes
were specified on the containing object.

These changes also included:
1. Dictionary typing was included for all the `to_dict`
   methods for clarity in subsequent usage.
2. `DataT` and `DataPointT` were did not include the
   exponential histogram types in point.py, and so those
   were added with new `to_json` and `to_dict` methods as
   well for consistency. It appears that the exponential
   types were added later and including them in the types
   might have been overlooked. Please let me know if that
   is a misunderstanding on my part.
3. OrderedDict was removed in a number of places
   associated with the existing `to_json` functionality
   given its redundancy for Python 3.7+ compatibility.
   I was assuming this was legacy code for previous
   compatibility, but please let me know if that's not
   the case as well.
4. `to_dict` was added to objects like `SpanContext`,
   `Link`, and `Event` that were previously being
   serialized by static methods within the `ReadableSpan`
   class and accessing private/protected members.
   This simplified the serialization in the `ReadableSpan`
   class and those methods were removed. However, once
   again, let me know if there was a larger purpose to
   those I could not find.

Finally, I used `to_dict` as the method names here to be
consistent with other related usages. For example,
`dataclasses.asdict()`. But, mostly because that was by
far the most popular usage within the larger community:

328k files found on GitHub that define `to_dict` functions,
which include some of the most popular Python libraries
to date:
https://github.com/search?q=%22def+to_dict%28%22+language%3APython&type=code&p=1&l=Python

versus

3.3k files found on GitHub that define `to_dictionary`
functions:
https://github.com/search?q=%22def+to_dictionary%28%22+language%3APython&type=code&l=Python

However, if there is a preference for this library to use
`to_dictionary` instead let me know and I will adjust.

Fixes #3364

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

@@ -103,6 +103,7 @@
     NonRecordingSpan,
     Span,
     SpanContext,
+    SpanContextDict,
     TraceFlags,
     TraceState,
     format_span_id,
@@ -130,6 +131,13 @@ def attributes(self) -> types.Attributes:
         pass
 
 
+class LinkDict(typing.TypedDict):
+    """Dictionary representation of a span Link."""
+
+    context: SpanContextDict
+    attributes: types.Attributes
+
+
 class Link(_LinkBase):
     """A link to a `Span`. The attributes of a Link are immutable.
 
@@ -152,6 +160,12 @@ def __init__(
     def attributes(self) -> types.Attributes:
         return self._attributes
 
+    def to_dict(self) -> LinkDict:
+        return {
+            "context": self.context.to_dict(),
+            "attributes": dict(self._attributes),
+        }
+
 
 _Links = Optional[Sequence[Link]]
 

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

@@ -403,6 +403,14 @@ def values(self) -> typing.ValuesView[str]:
 _SPAN_ID_MAX_VALUE = 2**64 - 1
 
 
+class SpanContextDict(typing.TypedDict):
+    """Dictionary representation of a SpanContext."""
+
+    trace_id: str
+    span_id: str
+    trace_state: typing.Dict[str, str]
+
+
 class SpanContext(
     typing.Tuple[int, int, bool, "TraceFlags", "TraceState", bool]
 ):
@@ -477,6 +485,13 @@ def trace_state(self) -> "TraceState":
     def is_valid(self) -> bool:
         return self[5]  # pylint: disable=unsubscriptable-object
 
+    def to_dict(self) -> SpanContextDict:
+        return {
+            "trace_id": f"0x{format_trace_id(self.trace_id)}",
+            "span_id": f"0x{format_span_id(self.span_id)}",
+            "trace_state": dict(self.trace_state),
+        }
+
     def __setattr__(self, *args: str) -> None:
         _logger.debug(
             "Immutable type, ignoring call to set attribute", stack_info=True

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

@@ -32,6 +32,13 @@ class StatusCode(enum.Enum):
     """The operation contains an error."""
 
 
+class StatusDict(typing.TypedDict):
+    """Dictionary representation of a trace Status."""
+
+    status_code: str
+    description: typing.Optional[str]
+
+
 class Status:
     """Represents the status of a finished Span.
 
@@ -80,3 +87,10 @@ def is_ok(self) -> bool:
     def is_unset(self) -> bool:
         """Returns true if unset, false otherwise."""
         return self._status_code is StatusCode.UNSET
+
+    def to_dict(self) -> StatusDict:
+        """Convert to a dictionary representation of the status."""
+        return {
+            "status_code": str(self.status_code.name),
+            "description": self.description,
+        }

opentelemetry-sdk/src/opentelemetry/sdk/_logs/_internal/__init__.py

@@ -19,6 +19,7 @@
 import logging
 import threading
 import traceback
+import typing
 from os import environ
 from time import time_ns
 from typing import Any, Callable, Optional, Tuple, Union
@@ -37,7 +38,7 @@
     OTEL_ATTRIBUTE_COUNT_LIMIT,
     OTEL_ATTRIBUTE_VALUE_LENGTH_LIMIT,
 )
-from opentelemetry.sdk.resources import Resource
+from opentelemetry.sdk.resources import Resource, ResourceDict
 from opentelemetry.sdk.util import ns_to_iso_str
 from opentelemetry.sdk.util.instrumentation import InstrumentationScope
 from opentelemetry.semconv.trace import SpanAttributes
@@ -147,6 +148,21 @@ def _from_env_if_absent(
 )
 
 
+class LogRecordDict(typing.TypedDict):
+    """Dictionary representation of a LogRecord."""
+
+    body: typing.Optional[typing.Any]
+    severity_number: int
+    severity_text: typing.Optional[str]
+    attributes: Attributes
+    dropped_attributes: int
+    timestamp: typing.Optional[str]
+    trace_id: str
+    span_id: str
+    trace_flags: typing.Optional[int]
+    resource: typing.Optional[ResourceDict]
+
+
 class LogRecord(APILogRecord):
     """A LogRecord instance represents an event being logged.
 
@@ -194,30 +210,28 @@ def __eq__(self, other: object) -> bool:
             return NotImplemented
         return self.__dict__ == other.__dict__
 
+    def to_dict(self) -> LogRecordDict:
+        return {
+            "body": self.body,
+            "severity_number": self.severity_number.value
+            if self.severity_number is not None
+            else SeverityNumber.UNSPECIFIED.value,
+            "severity_text": self.severity_text,
+            "attributes": dict(self.attributes or {}),
+            "dropped_attributes": self.dropped_attributes,
+            "timestamp": ns_to_iso_str(self.timestamp),
+            "trace_id": f"0x{format_trace_id(self.trace_id)}"
+            if self.trace_id is not None
+            else "",
+            "span_id": f"0x{format_span_id(self.span_id)}"
+            if self.span_id is not None
+            else "",
+            "trace_flags": self.trace_flags,
+            "resource": self.resource.to_dict() if self.resource else None,
+        }
+
     def to_json(self, indent=4) -> str:
-        return json.dumps(
-            {
-                "body": self.body,
-                "severity_number": repr(self.severity_number),
-                "severity_text": self.severity_text,
-                "attributes": dict(self.attributes)
-                if bool(self.attributes)
-                else None,
-                "dropped_attributes": self.dropped_attributes,
-                "timestamp": ns_to_iso_str(self.timestamp),
-                "trace_id": f"0x{format_trace_id(self.trace_id)}"
-                if self.trace_id is not None
-                else "",
-                "span_id": f"0x{format_span_id(self.span_id)}"
-                if self.span_id is not None
-                else "",
-                "trace_flags": self.trace_flags,
-                "resource": json.loads(self.resource.to_json())
-                if self.resource
-                else None,
-            },
-            indent=indent,
-        )
+        return json.dumps(self.to_dict(), indent=indent)
 
     @property
     def dropped_attributes(self) -> int: