python: change pytest pkg/__init__.py to only collect the __init__.py Module

[bluetech]

Previously it would collect the entire package, but this is not what users (including me) expect.

Refs #3749
Fixes #8976
Fixes #9263
Fixes #9313

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Technically I'd say this is a bug fix, but I'm not entirely sure the previous behavior wasn't intentional (there are certainly several tests to the contrary). And it also has potential of breaking users who somehow rely on the previous behavior. Therefore I've marked this as breaking, and it should not be merged before we decide the next version will be a major. Still, acks would be good already :)

[bluetech]

self.path here is the __init__.py file (== the path of the Package).

This says, if pkg/__init__.py was specified directly (e.g. pytest pkg/__init__.py), then collect its Module even if __init__.py is not a recognized pattern in python_files config.

The relevance of this to the bug is the following code in Session:

pytest/src/_pytest/main.py

Lines 805 to 818 in 4f3f36c

	# If __init__.py was the only file requested, then the matched
	# node will be the corresponding Package (by default), and the
	# first yielded item will be the __init__ Module itself, so
	# just use that. If this special case isn't taken, then all the
	# files in the package will be yielded.
	if argpath.name == "__init__.py" and isinstance(matching[0], Package):
	try:
	yield next(iter(matching[0].collect()))
	except StopIteration:
	# The package collects nothing with only an __init__.py
	# file in it, which gets ignored by the default
	# "python_files" option.
	pass
	continue

That code is currently broken.

[nicoddemus]

LGTM!

Should we add some note to the docs themselves, besides the CHANGELOG?

[bluetech]

Should we add some note to the docs themselves, besides the CHANGELOG?

Any suggestion where? I was thinking of adding a note to the deprecations page, but that only lists "Deprecated features" and "Removed features". Maybe change "Removed features" to "Removed features and breaking changes" and add it there?

[nicoddemus]

Any suggestion where? I was thinking of adding a note to the deprecations page, but that only lists "Deprecated features" and "Removed features". Maybe change "Removed features" to "Removed features and breaking changes" and add it there?

Yeah I was quickly browsing the docs and could not find any in-depth discussion about collection...

I think your suggestion is good. 👍