Use shortest module name for importlib imports

AUTHORS

@@ -309,6 +309,7 @@ Pavel Karateev
 Paweł Adamczak
 Pedro Algarvio
 Petter Strandmark
+Philipp A.
 Philipp Loose
 Pierre Sassoulas
 Pieter Mulder

changelog/11931.bugfix.rst

@@ -0,0 +1 @@
+Fix some instances of importing doctests’ parent modules when using `--import-mode=importlib`.

pyproject.toml

@@ -144,6 +144,7 @@ ignore = [
     "PLW2901",  # for loop variable overwritten by assignment target
     "PLR5501",  # Use `elif` instead of `else` then `if`
 ]
+allowed-confusables = ["’"]
 
 [tool.ruff.lint.pycodestyle]
 # In order to be able to format for 88 char in ruff format

src/_pytest/pathlib.py

@@ -607,21 +607,18 @@
 
 def module_name_from_path(path: Path, root: Path) -> str:
     """
-    Return a dotted module name based on the given path, anchored on root.
+    Return a dotted module name based on the given path,
+    anchored on root or the most likely entry in `sys.path`.
 
     For example: path="projects/src/tests/test_foo.py" and root="/projects", the
     resulting module name will be "src.tests.test_foo".
     """
     path = path.with_suffix("")
-    try:
-        relative_path = path.relative_to(root)
-    except ValueError:
-        # If we can't get a relative path to root, use the full path, except
-        # for the first part ("d:\\" or "/" depending on the platform, for example).
-        path_parts = path.parts[1:]
-    else:
-        # Use the parts for the relative path to the root path.
-        path_parts = relative_path.parts
+    candidates = (
+        _maybe_relative_parts(path, dir)
+        for dir in itertools.chain([root], map(Path, sys.path))
+    )
+    path_parts = min(candidates, key=len)  # type: ignore[arg-type]
 
     # Module name for packages do not contain the __init__ file, unless
     # the `__init__.py` file is at the root.
@@ -631,6 +628,17 @@
     return ".".join(path_parts)
 
 
+def _maybe_relative_parts(path: Path, root: Path) -> "tuple[str, ...]":
+    try:
+        relative_path = path.relative_to(root)
+    except ValueError:
+        # If we can't get a relative path to root, use the full path, except
+        # for the first part ("d:\\" or "/" depending on the platform, for example).
+        return path.parts[1:]
+    # Use the parts for the relative path to the root path.
+    return relative_path.parts
+
+
 def insert_missing_modules(modules: Dict[str, ModuleType], module_name: str) -> None:
     """
     Used by ``import_path`` to create intermediate modules when using mode=importlib.

testing/test_pathlib.py

@@ -669,6 +669,34 @@ def __init__(self) -> None:
         mod = import_path(init, root=tmp_path, mode=ImportMode.importlib)
         assert len(mod.instance.INSTANCES) == 1
 
+    def test_importlib_doctest(self, monkeypatch: MonkeyPatch, tmp_path: Path) -> None:
+        """
+        Importing a package using --importmode=importlib should
+        import the package using the canonical name
+        """
+        proj_dir = tmp_path / "proj"
+        proj_dir.mkdir()
+        pkgs_dir = tmp_path / "pkgs"
+        pkgs_dir.mkdir()
+        monkeypatch.chdir(proj_dir)
+        monkeypatch.syspath_prepend(pkgs_dir)
+        # this is also there, but shouldn’t be imported from
+        monkeypatch.syspath_prepend(proj_dir)
+
+        package_name = "importlib_doctest"
+        # pkgs_dir is second to set `init`
+        for directory in [proj_dir / "src", pkgs_dir]:
+            pkgdir = directory / package_name
+            pkgdir.mkdir(parents=True)
+            init = pkgdir / "__init__.py"
+            init.write_text("", encoding="ascii")
+
+        # the PyTest root is `proj_dir`, but the package is imported from `pkgs_dir`
+        mod = import_path(init, root=proj_dir, mode=ImportMode.importlib)
+        # assert that it’s imported with the canonical name, not “path.to.package.<name>”
+        mod_names = [n for n, m in sys.modules.items() if m is mod]
+        assert mod_names == ["importlib_doctest"]
+
     def test_importlib_root_is_package(self, pytester: Pytester) -> None:
         """
         Regression for importing a `__init__`.py file that is at the root