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

.changelog/5183.changed

@@ -0,0 +1 @@
+`opentelemetry-sdk`: tighten `ReadableSpan.attributes` return type to non-Optional `Mapping`

CHANGELOG.md

@@ -2,6 +2,14 @@
 
 All notable changes to this project will be documented in this file.
 
+<!--
+Do *NOT* add changelog entries here!
+
+This changelog is managed by towncrier and is compiled at release time.
+
+See https://github.com/open-telemetry/opentelemetry-python/blob/main/CONTRIBUTING.md#changelog for details.
+-->
+
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
@@ -10,8 +18,16 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 > [!IMPORTANT]
 > We are working on stabilizing the Log signal that would require making deprecations and breaking changes. We will try to reduce the releases that may require an update to your code, especially for instrumentations or for sdk developers.
 
+<!-- changelog start -->
+
 ## Unreleased
 
+- `opentelemetry-sdk`: fix multi-processor `force_flush` skipping remaining processors when one returns `None`
+  ([#5179](https://github.com/open-telemetry/opentelemetry-python/pull/5179))
+- 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 +58,22 @@ 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))
+- `opentelemetry-sdk`: add sampler plugin loading to declarative file configuration via the `opentelemetry_sampler` entry point group, matching the spec's PluginComponentProvider mechanism
+  ([#5095](https://github.com/open-telemetry/opentelemetry-python/pull/5095))
+- Add `registry` keyword argument to `PrometheusMetricReader` to allow passing a custom Prometheus registry
+  ([#5055](https://github.com/open-telemetry/opentelemetry-python/pull/5055))
+- Add ability to selectively enable exporting of SDK internal metrics with the `OTEL_PYTHON_SDK_INTERNAL_METRICS_ENABLED` environment variable.
+  ([#5151](https://github.com/open-telemetry/opentelemetry-python/pull/5151))
+- `opentelemetry-api`, `opentelemetry-sdk`: add support for 'random-trace-id' flags in W3C traceparent header trace flags. Implementations of `IdGenerator` that do randomly generate the 56 least significant bits, should also implement a `is_trace_id_random` methods that returns `True`.
+  ([#4854](https://github.com/open-telemetry/opentelemetry-python/pull/4854))
 
 ## Version 1.41.0/0.62b0 (2026-04-09)
 

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

@@ -497,7 +497,8 @@ def status(self) -> trace_api.Status:
         return self._status
 
     @property
-    def attributes(self) -> types.Attributes:
+    def attributes(self) -> Mapping[str, types.AttributeValue]:
+        # `or {}` keeps the return non-None; see #4569.
         return MappingProxyType(self._attributes or {})
 
     @property