sdk: tighten ReadableSpan.attributes to non-Optional Mapping (#4569)

CHANGELOG.md

@@ -12,6 +12,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## Unreleased
 
+- `opentelemetry-sdk`: tighten `ReadableSpan.attributes` annotation to non-Optional `Mapping` so callers don't need `assert ... is not None` boilerplate; runtime guarantee was already in place via `MappingProxyType(self._attributes or {})`
+  ([#5183](https://github.com/open-telemetry/opentelemetry-python/pull/5183))
+- Apply fixes for `UP` ruff rule
+  ([#5133](https://github.com/open-telemetry/opentelemetry-python/pull/5133))
+- Switch to SPDX license headers and add CI enforcement
+  ([#5177](https://github.com/open-telemetry/opentelemetry-python/pull/5177))
 - `opentelemetry-api`: Enforce W3C Baggage size limits on outbound propagation in `W3CBaggagePropagator.inject()`. Previously only inbound extraction enforced limits; now inject also caps entries at 180, individual pairs at 4096 bytes, and total header at 8192 bytes per the W3C Baggage spec. The extract path max_pairs limit now counts all size-valid entries rather than only successfully parsed ones.
   ([#5163](https://github.com/open-telemetry/opentelemetry-python/pull/5163))
 - `opentelemetry-sdk`: add `additional_properties` support to generated config models via custom `datamodel-codegen` template, enabling plugin/custom component names to flow through typed dataclasses
@@ -42,6 +48,14 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   ([#5135](https://github.com/open-telemetry/opentelemetry-python/pull/5135))
 - ci: wait for tracecontext server readiness instead of a fixed sleep in `scripts/tracecontext-integration-test.sh`
   ([#5149](https://github.com/open-telemetry/opentelemetry-python/pull/5149))
+- `opentelemetry-api`: update `EnvironmentGetter` and `EnvironmentSetter` to use normalized environment variable names
+  ([#5119](https://github.com/open-telemetry/opentelemetry-python/pull/5119))
+- `opentelemetry-sdk`: only load entrypoints for resource detectors if they are configured via `OTEL_EXPERIMENTAL_RESOURCE_DETECTORS`
+  ([#5145](https://github.com/open-telemetry/opentelemetry-python/pull/5145))
+- `opentelemetry-exporter-otlp-json-common`: add 'opentelemetry-exporter-otlp-json-common' package for OTLP JSON exporters
+  ([#4996](https://github.com/open-telemetry/opentelemetry-python/pull/4996))
+- `opentelemetry-exporter-otlp-proto-grpc`: make retryable gRPC error codes configurable for gRPC exporters
+  ([#4917](https://github.com/open-telemetry/opentelemetry-python/pull/4917))
 
 ## Version 1.41.0/0.62b0 (2026-04-09)
 

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

@@ -497,7 +497,12 @@ def status(self) -> trace_api.Status:
         return self._status
 
     @property
-    def attributes(self) -> types.Attributes:
+    def attributes(self) -> Mapping[str, types.AttributeValue]:
+        # The implementation always returns a MappingProxyType, never None,
+        # because `self._attributes or {}` falls back to an empty dict.
+        # Tightening the return annotation fixes type-checker complaints
+        # like `Object of type "None" is not subscriptable` when callers
+        # do `span.attributes["key"]`. See issue #4569.
         return MappingProxyType(self._attributes or {})
 
     @property