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

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

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

changelog/8976.breaking.rst

@@ -0,0 +1,5 @@
+Running `pytest pkg/__init__.py` now collects the `pkg/__init__.py` file (module) only.
+Previously, it collected the entire `pkg` package, including other test files in the directory, but excluding tests in the `__init__.py` file itself
+(unless :confval:`python_files` was changed to allow `__init__.py` file).
+
+To collect the entire package, specify just the directory: `pytest pkg`.

doc/en/deprecations.rst

@@ -467,12 +467,26 @@ The ``yield_fixture`` function/decorator
 It has been so for a very long time, so can be search/replaced safely.
 
 
-Removed Features
-----------------
+Removed Features and Breaking Changes
+-------------------------------------
 
 As stated in our :ref:`backwards-compatibility` policy, deprecated features are removed only in major releases after
 an appropriate period of deprecation has passed.
 
+Some breaking changes which could not be deprecated are also listed.
+
+
+Collecting ``__init__.py`` files no longer collects package
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. versionremoved:: 8.0
+
+Running `pytest pkg/__init__.py` now collects the `pkg/__init__.py` file (module) only.
+Previously, it collected the entire `pkg` package, including other test files in the directory, but excluding tests in the `__init__.py` file itself
+(unless :confval:`python_files` was changed to allow `__init__.py` file).
+
+To collect the entire package, specify just the directory: `pytest pkg`.
+
 
 The ``pytest.collect`` module
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

src/_pytest/python.py

@@ -736,7 +736,9 @@ class Package(Module):
         this_path = self.path.parent
 
         # Always collect the __init__ first.
-        if path_matches_patterns(self.path, self.config.getini("python_files")):
+        if self.session.isinitpath(self.path) or path_matches_patterns(
+            self.path, self.config.getini("python_files")
+        ):
             yield Module.from_parent(self, path=self.path)
 
         pkg_prefixes: Set[Path] = set()

testing/example_scripts/collect/package_init_given_as_arg/pkg/__init__.py

@@ -0,0 +1,2 @@
+def test_init():
+    pass

testing/example_scripts/collect/package_init_given_as_arg/pkg/test_foo.py

@@ -1,2 +1,2 @@
-def test():
+def test_foo():
     pass

testing/python/collect.py

@@ -1420,10 +1420,15 @@ def test_package_collection_infinite_recursion(pytester: Pytester) -> None:
 
 
 def test_package_collection_init_given_as_argument(pytester: Pytester) -> None:
-    """Regression test for #3749"""
+    """Regression test for #3749, #8976, #9263, #9313.
+
+    Specifying an __init__.py file directly should collect only the __init__.py
+    Module, not the entire package.
+    """
     p = pytester.copy_example("collect/package_init_given_as_arg")
-    result = pytester.runpytest(p / "pkg" / "__init__.py")
-    result.stdout.fnmatch_lines(["*1 passed*"])
+    items, hookrecorder = pytester.inline_genitems(p / "pkg" / "__init__.py")
+    assert len(items) == 1
+    assert items[0].name == "test_init"
 
 
 def test_package_with_modules(pytester: Pytester) -> None:

testing/test_collection.py

@@ -1392,19 +1392,27 @@ def test_collect_pkg_init_and_file_in_args(pytester: Pytester) -> None:
     p = subdir.joinpath("test_file.py")
     p.write_text("def test_file(): pass", encoding="utf-8")
 
-    # NOTE: without "-o python_files=*.py" this collects test_file.py twice.
-    # This changed/broke with "Add package scoped fixtures #2283" (2b1410895)
-    # initially (causing a RecursionError).
-    result = pytester.runpytest("-v", str(init), str(p))
+    # Just the package directory, the __init__.py module is filtered out.
+    result = pytester.runpytest("-v", subdir)
     result.stdout.fnmatch_lines(
         [
             "sub/test_file.py::test_file PASSED*",
+            "*1 passed in*",
+        ]
+    )
+
+    # But it's included if specified directly.
+    result = pytester.runpytest("-v", init, p)
+    result.stdout.fnmatch_lines(
+        [
+            "sub/__init__.py::test_init PASSED*",
             "sub/test_file.py::test_file PASSED*",
             "*2 passed in*",
         ]
     )
 
-    result = pytester.runpytest("-v", "-o", "python_files=*.py", str(init), str(p))
+    # Or if the pattern allows it.
+    result = pytester.runpytest("-v", "-o", "python_files=*.py", subdir)
     result.stdout.fnmatch_lines(
         [
             "sub/__init__.py::test_init PASSED*",
@@ -1419,10 +1427,13 @@ def test_collect_pkg_init_only(pytester: Pytester) -> None:
     init = subdir.joinpath("__init__.py")
     init.write_text("def test_init(): pass", encoding="utf-8")
 
-    result = pytester.runpytest(str(init))
+    result = pytester.runpytest(subdir)
     result.stdout.fnmatch_lines(["*no tests ran in*"])
 
-    result = pytester.runpytest("-v", "-o", "python_files=*.py", str(init))
+    result = pytester.runpytest("-v", init)
+    result.stdout.fnmatch_lines(["sub/__init__.py::test_init PASSED*", "*1 passed in*"])
+
+    result = pytester.runpytest("-v", "-o", "python_files=*.py", subdir)
     result.stdout.fnmatch_lines(["sub/__init__.py::test_init PASSED*", "*1 passed in*"])
 
 

testing/test_doctest.py

@@ -114,7 +114,7 @@ class TestDoctests:
         reprec.assertoutcome(failed=1)
 
     def test_importmode(self, pytester: Pytester):
-        p = pytester.makepyfile(
+        pytester.makepyfile(
             **{
                 "namespacepkg/innerpkg/__init__.py": "",
                 "namespacepkg/innerpkg/a.py": """
@@ -132,7 +132,7 @@ class TestDoctests:
                 """,
             }
         )
-        reprec = pytester.inline_run(p, "--doctest-modules", "--import-mode=importlib")
+        reprec = pytester.inline_run("--doctest-modules", "--import-mode=importlib")
         reprec.assertoutcome(passed=1)
 
     def test_new_pattern(self, pytester: Pytester):

testing/test_nose.py

@@ -504,7 +504,7 @@ def test_nose_setup_skipped_if_non_callable(pytester: Pytester) -> None:
             pass
         """,
     )
-    result = pytester.runpytest(p, "-p", "nose")
+    result = pytester.runpytest(p.parent, "-p", "nose")
     assert result.ret == 0