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 pytest-dev#3749
Fixes pytest-dev#8976
Fixes pytest-dev#9263
Fixes pytest-dev#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`.

src/_pytest/python.py

@@ -747,7 +747,10 @@ def collect(self) -> Iterable[Union[nodes.Item, nodes.Collector]]:
         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 @@
+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

@@ -1407,10 +1407,15 @@ 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

@@ -1362,19 +1362,27 @@ 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")
 
-    # 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*",
@@ -1389,10 +1397,13 @@ def test_collect_pkg_init_only(pytester: Pytester) -> None:
     init = subdir.joinpath("__init__.py")
     init.write_text("def test_init(): pass")
 
-    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_nose.py

@@ -494,7 +494,7 @@ def test_it():
             pass
         """,
     )
-    result = pytester.runpytest(p, "-p", "nose")
+    result = pytester.runpytest(p.parent, "-p", "nose")
     assert result.ret == 0