Conditionally ignore collection of setuptools dirnames

changelog/12625.improvement.rst

@@ -0,0 +1,4 @@
+Conditionally ignore collection of setuptools artifacts dirnames only if the
+directories reside inside a setuptools project, i.e. `setup.cfg` is present alongside
+a `setup.py` or a `pyproject.toml` with setuptools configuration inside.
+You can use the new `--collect-in-build` to force collection of ignored directories.

doc/en/reference/reference.rst

@@ -1754,7 +1754,7 @@ passed multiple times. The expected format is ``name=value``. For example::
         [seq]   matches any character in seq
         [!seq]  matches any char not in seq
 
-   Default patterns are ``'*.egg'``, ``'.*'``, ``'_darcs'``, ``'build'``,
+   Default patterns are ``'*.egg'``, ``'.*'``, ``'_darcs'``,
    ``'CVS'``, ``'dist'``, ``'node_modules'``, ``'venv'``, ``'{arch}'``.
    Setting a ``norecursedirs`` replaces the default.  Here is an example of
    how to avoid certain directories:
@@ -1776,6 +1776,9 @@ passed multiple times. The expected format is ``name=value``. For example::
    *must* override ``norecursedirs`` in addition to using the
    ``--collect-in-virtualenv`` flag.
 
+   Similarly, pytest will attempt to intelligently identify and igmore build
+   artifacts of a setuptools project unless ``--collect-in-build`` is used.
+
 
 .. confval:: python_classes
 
@@ -2163,6 +2166,8 @@ All the command-line flags can be obtained by running ``pytest --help``::
       --keep-duplicates     Keep duplicate tests
       --collect-in-virtualenv
                             Don't ignore tests in a local virtualenv directory
+      --collect-in-build
+                            Don't ignore tests in a local build directory
       --import-mode={prepend,append,importlib}
                             Prepend/append to sys.path when importing test
                             modules and conftest files. Default: prepend.

src/_pytest/main.py

@@ -56,15 +56,13 @@
 def pytest_addoption(parser: Parser) -> None:
     parser.addini(
         "norecursedirs",
-        "Directory patterns to avoid for recursion",
+        "Directory patterns to avoid collecting (defaults to ignore build artifacts)",
         type="args",
         default=[
             "*.egg",
             ".*",
             "_darcs",
-            "build",
             "CVS",
-            "dist",
             "node_modules",
             "venv",
             "{arch}",
@@ -218,6 +216,13 @@ def pytest_addoption(parser: Parser) -> None:
         default=False,
         help="Don't ignore tests in a local virtualenv directory",
     )
+    group.addoption(
+        "--collect-in-build",
+        action="store_true",
+        dest="collect_in_build",
+        default=False,
+        help="Don't ignore builds in a local build/dist artifacts directory",
+    )
     group.addoption(
         "--import-mode",
         default="prepend",
@@ -371,6 +376,50 @@ def pytest_runtestloop(session: Session) -> bool:
     return True
 
 
+def _is_setuptools_in_pyproject_toml(toml: Path) -> bool:
+    """Attempt to decode a toml file into a dict, returning None if fails."""
+    if sys.version_info >= (3, 11):
+        import tomllib
+    else:
+        import tomli as tomllib
+
+    try:
+        toml_text = toml.read_text(encoding="utf-8")
+        parsed_toml = tomllib.loads(toml_text)
+        build_system = parsed_toml.get("build-system", {}).get("requires")
+        if "setuptools" in build_system:
+            return True
+    except tomllib.TOMLDecodeError:
+        # Not a valid Toml, so no setuptools.
+        pass
+
+    return False
+
+
+def _in_build(path: Path) -> bool:
+    """Detect if ``path`` is the root of a buildsystem's artifacts
+    by checking known dirnames patterns, and the presence of configuration in
+    the parent dir by checking for a setup.py, setup.cfg, or pyproject.toml.
+    """
+    if not path.is_dir():
+        return False
+
+    setup_cfg = path.parent / "setup.cfg"
+    if not setup_cfg.is_file():
+        return False
+
+    if any(fnmatch_ex(pat, path) for pat in ("build", "dist")):
+        setup_py = path.parent / "setup.py"
+        if setup_py.is_file():
+            return True
+
+        toml = path.parent / "pyproject.toml"
+        if toml.is_file() and _is_setuptools_in_pyproject_toml(toml):
+            return True
+
+    return False
+
+
 def _in_venv(path: Path) -> bool:
     """Attempt to detect if ``path`` is the root of a Virtual Environment by
     checking for the existence of the pyvenv.cfg file.
@@ -422,6 +471,10 @@ def pytest_ignore_collect(collection_path: Path, config: Config) -> bool | None:
     if not allow_in_venv and _in_venv(collection_path):
         return True
 
+    allow_in_build = config.getoption("collect_in_build")
+    if not allow_in_build and _in_build(collection_path):
+        return True
+
     if collection_path.is_dir():
         norecursepatterns = config.getini("norecursedirs")
         if any(fnmatch_ex(pat, collection_path) for pat in norecursepatterns):

testing/test_collection.py

@@ -137,8 +137,6 @@ def test_foo():
 class TestCollectFS:
     def test_ignored_certain_directories(self, pytester: Pytester) -> None:
         tmp_path = pytester.path
-        ensure_file(tmp_path / "build" / "test_notfound.py")
-        ensure_file(tmp_path / "dist" / "test_notfound.py")
         ensure_file(tmp_path / "_darcs" / "test_notfound.py")
         ensure_file(tmp_path / "CVS" / "test_notfound.py")
         ensure_file(tmp_path / "{arch}" / "test_notfound.py")
@@ -276,6 +274,59 @@ def test_missing_permissions_on_unselected_directory_doesnt_crash(
         assert result.ret == ExitCode.OK
         result.assert_outcomes(passed=1)
 
+    known_build_dirs = pytest.mark.parametrize("build_dir", ["build", "dist"])
+
+    @known_build_dirs
+    def test_build_dirs_ignored_when_setuptools_setup_py_present(
+        self, pytester: Pytester, build_dir: str
+    ) -> None:
+        tmp_path = pytester.path
+        ensure_file(tmp_path / build_dir / "test_module.py").write_text(
+            "def test_hello(): pass", encoding="utf-8"
+        )
+
+        result = pytester.runpytest("--collect-only").stdout.str()
+        assert "test_module" in result
+
+        ensure_file(tmp_path / "setup.cfg")
+
+        result = pytester.runpytest("--collect-only").stdout.str()
+        assert "test_module" in result
+
+        ensure_file(tmp_path / "setup.py")
+        result = pytester.runpytest("--collect-only").stdout.str()
+        assert "test_module" not in result
+
+        result = pytester.runpytest("--collect-only", "--collect-in-build").stdout.str()
+        assert "test_module" in result
+
+    @known_build_dirs
+    def test_build_dirs_ignored_when_setuptools_present_in_pyproject_toml(
+        self, pytester: Pytester, build_dir: str
+    ) -> None:
+        tmp_path = pytester.path
+        ensure_file(tmp_path / build_dir / "test_module.py").write_text(
+            "def test_hello(): pass", encoding="utf-8"
+        )
+
+        result = pytester.runpytest("--collect-only").stdout.str()
+        assert "test_module" in result
+
+        ensure_file(tmp_path / "setup.cfg")
+
+        result = pytester.runpytest("--collect-only").stdout.str()
+        assert "test_module" in result
+
+        ensure_file(tmp_path / "pyproject.toml").write_text(
+            '[build-system]\nrequires = ["setuptools", "setuptools-scm"]\n',
+            encoding="utf-8",
+        )
+        result = pytester.runpytest("--collect-only").stdout.str()
+        assert "test_module" not in result
+
+        result = pytester.runpytest("--collect-only", "--collect-in-build").stdout.str()
+        assert "test_module" in result
+
 
 class TestCollectPluginHookRelay:
     def test_pytest_collect_file(self, pytester: Pytester) -> None: