From 262f2751d905942264b1ec9db9b5a03110961be6 Mon Sep 17 00:00:00 2001
From: Nick Stenning <nick@whiteink.com>
Date: Thu, 23 Apr 2026 13:26:20 +0200
Subject: [PATCH] Use a covariant type for detectors argument

This updates the type annotation for `get_aggregated_resources`'s
`detectors` argument to use `collections.abc.Sequence`, which is
covariant in its type parameter and thus has the expected behaviour for
an input type.

`typing.List` is invariant in its type parameter, which means that a
simple list of `ResourceDetector` subclasses is not a
`list[ResourceDetector]`.

Some typecheckers are more lenient than others, but [ty] enforces this
and thus the following code does not typecheck despite being
semantically correct.

    from opentelemetry.sdk.resources import (
        OsResourceDetector,
        ProcessResourceDetector,
        Resource,
        get_aggregated_resources,
    )
    from opentelemetry.sdk.trace import TracerProvider

    resource = Resource.create()

    resource_detectors = [
        ProcessResourceDetector(),
        OsResourceDetector(),
    ]

    tracer_provider = TracerProvider(
        resource=get_aggregated_resources(
            detectors=resource_detectors,
            initial_resource=resource,
        ),
    )

The full output of ty is as follows:

    $ uv run ty check
    error[invalid-argument-type]: Argument to function `get_aggregated_resources` is incorrect
      --> test.py:18:9
       |
    18 |         detectors=resource_detectors,
       |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Expected `list[ResourceDetector]`, found `list[ProcessResourceDetector | OsResourceDetector]`
       |
    info: Function defined here
       --> .venv/lib/python3.13/site-packages/opentelemetry/sdk/resources/__init__.py:507:5
        |
    507 | def get_aggregated_resources(
        |     ^^^^^^^^^^^^^^^^^^^^^^^^
    508 |     detectors: typing.List["ResourceDetector"],
        |     ------------------------------------------ Parameter declared here
        |
    info: `list` is invariant in its type parameter
    info: Consider using the covariant supertype `collections.abc.Sequence`
    info: For more information, see https://docs.astral.sh/ty/reference/typing-faq/#invariant-generics

    Found 1 diagnostic

[ty]: https://docs.astral.sh/ty/reference/typing-faq/#invariant-generics
---
 CHANGELOG.md                                                  | 2 ++
 opentelemetry-sdk/src/opentelemetry/sdk/resources/__init__.py | 3 ++-
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2e56e7357c..15130d85ef 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -34,6 +34,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   ([#5120](https://github.com/open-telemetry/opentelemetry-python/pull/5120))
 - Add WeaverLiveCheck test util
   ([#5088](https://github.com/open-telemetry/opentelemetry-python/pull/5088))
+- Fix incorrect type annotation on `detectors` parameter of `get_aggregated_resources`
+  ([#5135](https://github.com/open-telemetry/opentelemetry-python/pull/5135))
 
 ## Version 1.41.0/0.62b0 (2026-04-09)
 
diff --git a/opentelemetry-sdk/src/opentelemetry/sdk/resources/__init__.py b/opentelemetry-sdk/src/opentelemetry/sdk/resources/__init__.py
index beb21098e1..9e3c194770 100644
--- a/opentelemetry-sdk/src/opentelemetry/sdk/resources/__init__.py
+++ b/opentelemetry-sdk/src/opentelemetry/sdk/resources/__init__.py
@@ -67,6 +67,7 @@
 import socket
 import sys
 import typing
+from collections.abc import Sequence
 from json import dumps
 from os import environ
 from types import ModuleType
@@ -517,7 +518,7 @@ def detect(self) -> "Resource":
 
 
 def get_aggregated_resources(
-    detectors: typing.List["ResourceDetector"],
+    detectors: Sequence["ResourceDetector"],
     initial_resource: typing.Optional[Resource] = None,
     timeout: int = 5,
 ) -> "Resource":