gh-117505: Run ensurepip in isolated env in Windows installer (GH-118257)

ensurepip forks a subprocess to run pip itself, but that subprocess only inherits a -I isolated mode flag (see _run_pip() in Lib/ensurepip/__init__.py), not the "-E -s" flags that the installer has been using. This means that parts of ensurepip don't actually run in an isolated environment and can make incorrect decisions based on packages installed in the user site-packages.
(cherry picked from commit c9073eb1a99606df1efeb8959e9f11a8ebc23ae2)

Co-authored-by: Michael Vincent <377567+Vynce@users.noreply.github.com>

diff --git a/Misc/NEWS.d/next/Windows/2024-04-24-22-50-33.gh-issue-117505.gcTb_p.rst b/Misc/NEWS.d/next/Windows/2024-04-24-22-50-33.gh-issue-117505.gcTb_p.rst
new file mode 100644 (file)
index 0000000..0931687
--- /dev/null
+++ b/Misc/NEWS.d/next/Windows/2024-04-24-22-50-33.gh-issue-117505.gcTb_p.rst
@@ -0,0 +1 @@
+Fixes an issue with the Windows installer not running ensurepip in a fully isolated environment. This could cause unexpected interactions with the user site-packages.

diff --git a/Tools/msi/pip/pip.wxs b/Tools/msi/pip/pip.wxs
index 1d8083cad91a565e1d7727f2944e6fb7c5d8f8d9..627c4710a9fdfaa638cea4645cf81c8d641d7106 100644 (file)
--- a/Tools/msi/pip/pip.wxs
+++ b/Tools/msi/pip/pip.wxs
@@ -25,8 +25,8 @@
         <?endif ?>
         
         <!-- Install/uninstall pip -->
-        <CustomAction Id="SetUpdatePipCommandLine" Property="UpdatePip" Value='"[PYTHON_EXE]" -E -s -m ensurepip -U --default-pip' Execute="immediate" />
-        <CustomAction Id="SetRemovePipCommandLine" Property="UpdatePip" Value='"[PYTHON_EXE]" -E -s -B -m ensurepip._uninstall' Execute="immediate" />
+        <CustomAction Id="SetUpdatePipCommandLine" Property="UpdatePip" Value='"[PYTHON_EXE]" -I -m ensurepip -U --default-pip' Execute="immediate" />
+        <CustomAction Id="SetRemovePipCommandLine" Property="UpdatePip" Value='"[PYTHON_EXE]" -I -B -m ensurepip._uninstall' Execute="immediate" />
         
         <InstallExecuteSequence>
             <Custom Action="SetUpdatePipCommandLine" Before="UpdatePip">(&amp;DefaultFeature=3) AND NOT (!DefaultFeature=3)</Custom>