Avoid unnecessarily changing package_dir

And also avoid using './' paths

1 files changed, 12 insertions, 12 deletions

diff --git a/setuptools/config/expand.py b/setuptools/config/expand.py
index 3985040c..04442bd8 100644
--- a/setuptools/config/expand.py
+++ b/setuptools/config/expand.py
@@ -292,8 +292,8 @@ def find_packages(
 
     :rtype: list
     """
-
-    from setuptools.discovery import remove_nested_packages
+    from setuptools.discovery import construct_package_dir
+    from setuptools.extern.more_itertools import unique_everseen, always_iterable
 
     if namespaces:
         from setuptools.discovery import PEP420PackageFinder as PackageFinder
@@ -302,18 +302,18 @@ def find_packages(
 
     root_dir = root_dir or os.curdir
     where = kwargs.pop('where', ['.'])
-    if isinstance(where, str):
-        where = [where]
-
-    packages = []
+    packages: List[str] = []
     fill_package_dir = {} if fill_package_dir is None else fill_package_dir
-    for path in where:
-        pkgs = PackageFinder.find(_nest_path(root_dir, path), **kwargs)
+
+    for path in unique_everseen(always_iterable(where)):
+        package_path = _nest_path(root_dir, path)
+        pkgs = PackageFinder.find(package_path, **kwargs)
         packages.extend(pkgs)
-        if fill_package_dir.get("") != path:
-            parent_pkgs = remove_nested_packages(pkgs)
-            parent = {pkg: "/".join([path, *pkg.split(".")]) for pkg in parent_pkgs}
-            fill_package_dir.update(parent)
+        if pkgs and not (
+            fill_package_dir.get("") == path
+            or os.path.samefile(package_path, root_dir)
+        ):
+            fill_package_dir.update(construct_package_dir(pkgs, path))
 
     return packages