Apply pythonpath option as early as possible (#12536)

This allows plugins loaded via '-p' to benefit from the new PYTHONPATH, making the option useful in more cases and less surprising.

For this to work it was required for the functionality to be part of Config rather than a separate plugin, which is unfortunate but in the end considered a small price to pay.

Fix #11118.

---------

Co-authored-by: Bruno Oliveira <[email protected]>

Author: millerdev

changelog/11118.improvement.rst

@@ -0,0 +1,3 @@
+Now :confval:`pythonpath` configures `$PYTHONPATH` earlier than before during the initialization process, which now also affects plugins loaded via the `-p` command-line option.
+
+-- by :user:`millerdev`

doc/en/reference/reference.rst

@@ -1796,11 +1796,6 @@ passed multiple times. The expected format is ``name=value``. For example::
         [pytest]
         pythonpath = src1 src2
 
-   .. note::
-
-        ``pythonpath`` does not affect some imports that happen very early,
-        most notably plugins loaded using the ``-p`` command line option.
-
 
 .. confval:: required_plugins
 

src/_pytest/config/__init__.py

@@ -268,7 +268,6 @@ def directory_arg(path: str, optname: str) -> str:
     "warnings",
     "logging",
     "reports",
-    "python_path",
     "unraisableexception",
     "threadexception",
     "faulthandler",
@@ -1245,6 +1244,9 @@ def _initini(self, args: Sequence[str]) -> None:
         self._parser.extra_info["inifile"] = str(self.inipath)
         self._parser.addini("addopts", "Extra command line options", "args")
         self._parser.addini("minversion", "Minimally required pytest version")
+        self._parser.addini(
+            "pythonpath", type="paths", help="Add paths to sys.path", default=[]
+        )
         self._parser.addini(
             "required_plugins",
             "Plugins that must be present for pytest to run",
@@ -1294,6 +1296,18 @@ def _mark_plugins_for_rewrite(self, hook) -> None:
         for name in _iter_rewritable_modules(package_files):
             hook.mark_rewrite(name)
 
+    def _configure_python_path(self) -> None:
+        # `pythonpath = a b` will set `sys.path` to `[a, b, x, y, z, ...]`
+        for path in reversed(self.getini("pythonpath")):
+            sys.path.insert(0, str(path))
+        self.add_cleanup(self._unconfigure_python_path)
+
+    def _unconfigure_python_path(self) -> None:
+        for path in self.getini("pythonpath"):
+            path_str = str(path)
+            if path_str in sys.path:
+                sys.path.remove(path_str)
+
     def _validate_args(self, args: list[str], via: str) -> list[str]:
         """Validate known args."""
         self._parser._config_source_hint = via  # type: ignore
@@ -1370,6 +1384,7 @@ def _preparse(self, args: list[str], addopts: bool = True) -> None:
         )
         self._checkversion()
         self._consider_importhook(args)
+        self._configure_python_path()
         self.pluginmanager.consider_preparse(args, exclude_only=False)
         if not os.environ.get("PYTEST_DISABLE_PLUGIN_AUTOLOAD"):
             # Don't autoload from distribution package entry point. Only

src/_pytest/python_path.py

@@ -1409,7 +1409,6 @@ def pytest_load_initial_conftests(self):
         ("_pytest.config", "nonwrapper"),
         (m.__module__, "nonwrapper"),
         ("_pytest.legacypath", "nonwrapper"),
-        ("_pytest.python_path", "nonwrapper"),
         ("_pytest.capture", "wrapper"),
         ("_pytest.warnings", "wrapper"),
     ]

testing/test_config.py

@@ -3,7 +3,6 @@
 
 import sys
 from textwrap import dedent
-from typing import Generator
 
 from _pytest.pytester import Pytester
 import pytest
@@ -62,6 +61,27 @@ def test_two_dirs(pytester: Pytester, file_structure) -> None:
     result.assert_outcomes(passed=2)
 
 
+def test_local_plugin(pytester: Pytester, file_structure) -> None:
+    """`pythonpath` kicks early enough to load plugins via -p (#11118)."""
+    localplugin_py = pytester.path / "sub" / "localplugin.py"
+    content = dedent(
+        """
+        def pytest_load_initial_conftests():
+            print("local plugin load")
+
+        def pytest_unconfigure():
+            print("local plugin unconfig")
+        """
+    )
+    localplugin_py.write_text(content, encoding="utf-8")
+
+    pytester.makeini("[pytest]\npythonpath=sub\n")
+    result = pytester.runpytest("-plocalplugin", "-s", "test_foo.py")
+    result.stdout.fnmatch_lines(["local plugin load", "local plugin unconfig"])
+    assert result.ret == 0
+    result.assert_outcomes(passed=1)
+
+
 def test_module_not_found(pytester: Pytester, file_structure) -> None:
     """Without the pythonpath setting, the module should not be found."""
     pytester.makefile(".ini", pytest="[pytest]\n")
@@ -95,16 +115,13 @@ def test_clean_up(pytester: Pytester) -> None:
     after: list[str] | None = None
 
     class Plugin:
-        @pytest.hookimpl(wrapper=True, tryfirst=True)
-        def pytest_unconfigure(self) -> Generator[None, None, None]:
-            nonlocal before, after
+        @pytest.hookimpl(tryfirst=True)
+        def pytest_unconfigure(self) -> None:
+            nonlocal before
             before = sys.path.copy()
-            try:
-                return (yield)
-            finally:
-                after = sys.path.copy()
 
     result = pytester.runpytest_inprocess(plugins=[Plugin()])
+    after = sys.path.copy()
     assert result.ret == 0
 
     assert before is not None