With 8.2.0, attempt to import docs from niece module fails

[jaraco]

This issue is perhaps one of the weirdest and most obscure I've seen. My investigation began in jaraco/jaraco.xonsh#1. The summary is this:

• In GitHub actions (only), during collection, when attempting to collect docs/conf.py, something outside the call stack attempts to import jaraco.xonsh.docs, even though jaraco.xonsh is a module and docs is a sibling of jaraco.
• The issue is present in multiple Python versions (at least 3.10-3.12).
• The issue does not replicate when testing locally (either in a Linux Docker container or in macOS).
• The issue does replicate when using act to simulate the GitHub actions using Docker.
• Pinning to pytest<8.2 suppresses the failure.
• Disabling the xonsh plugin suppresses the failure.
• Note that jaraco.xonsh is a xonsh module in a PEP 420 namespace.
• Importing jaraco.xonsh might not be problematic except:
  • xonsh itself has a pytest plugin that configures subprocesses to raise on error
• The jaraco.xonsh module hasn't been collected or tested (in earlier runs or with pytest 8.2 when it passes locally).

As you might imagine, creating a minimal example is near impossible given the peculiarities of this scenario. The jaraco.xonsh project is nearly a minimal example in itself. The easiest way to replicate the issue is to clone the project at 249226010f9c9e5490dab851947efba2dceecb63, install act, and run the command in jaraco/jaraco.xonsh#1 (comment).

Questions for which I'm hoping to find answers:

• What is it about GHA that the issue only occurs there?
• What is it that's trying to import jaraco.xonsh.docs and why doesn't it show up in the stack trace?
• What's new in pytest 8.2 that would trigger this behavior?
• How is it that collecting "docs/conf.py" would ever try to import "jaraco.xonsh.docs"?

[The-Compiler]

What's new in pytest 8.2 that would trigger this behavior?

I somewhat painstakingly bisected this by using your act command and adjusting

diff --git i/pyproject.toml w/pyproject.toml
index ebdbf83..1fbe042 100644
--- i/pyproject.toml
+++ w/pyproject.toml
@@ -30,7 +30,7 @@ Homepage = "https://github.com/jaraco/jaraco.xonsh"
 [project.optional-dependencies]
 testing = [
 	# upstream
-	"pytest >= 6, != 8.1.1",
+	"pytest @ git+https://github.com/pytest-dev/pytest@17fc20af78d0c7b739806c4e461d2c9b8c30ceeb",
 	"pytest-checkdocs >= 2.4",
 	"pytest-cov",
 	"pytest-mypy",

accordingly.

This points me to 9989063, see:

• Refine how we detect namespace packages #12169
• pytest==8.1.1 Import regression in some namespace package layouts #12112