Use shortest module name

src/_pytest/pathlib.py

@@ -607,11 +607,20 @@ else:
 
 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".
     """
+    candidates = (
+        _module_name_from_path(path, dir)
+        for dir in itertools.chain([root], map(Path, sys.path))
+    )
+    return ".".join(min(candidates, key=len))
+
+
+def _module_name_from_path(path: Path, root: Path) -> tuple[str, ...]:
     path = path.with_suffix("")
     try:
         relative_path = path.relative_to(root)
@@ -628,7 +637,7 @@ def module_name_from_path(path: Path, root: Path) -> str:
     if len(path_parts) >= 2 and path_parts[-1] == "__init__":
         path_parts = path_parts[:-1]
 
-    return ".".join(path_parts)
+    return path_parts
 
 
 def insert_missing_modules(modules: Dict[str, ModuleType], module_name: str) -> None:

testing/test_pathlib.py

@@ -669,6 +669,33 @@ class TestImportLibMode:
         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):
+        """
+        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")
+
+        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