Reintroduce setup.py changes from #8280 erased by piper import #8902 (#8981)

Create install_python_interpreters.ps1
Install python38/39 on windows

Co-authored-by: Jie Luo <jieluo@google.com>

kokoro/release/python/windows/build_artifacts.bat

@@ -62,6 +62,8 @@ SET PYTHON_VERSION=3.7
 SET PYTHON_ARCH=64
 CALL build_single_artifact.bat || goto :error
 
+powershell -File kokoro/release/python/windows/install_python_interpreters.ps1
+
 SET PYTHON=C:\python38_32bit
 SET PYTHON_VERSION=3.8
 SET PYTHON_ARCH=32

kokoro/release/python/windows/install_python_interpreters.ps1

@@ -0,0 +1,97 @@
+#!/usr/bin/env powershell
+# Install Python 3.8 for x64 and x86 in order to build wheels on Windows.
+# Originally from grpc/tools/internal_ci/helper_scripts/install_python_interpreters.ps1
+
+Set-StrictMode -Version 2
+$ErrorActionPreference = 'Stop'
+
+trap {
+    $ErrorActionPreference = "Continue"
+    Write-Error $_
+    exit 1
+}
+
+# Avoid "Could not create SSL/TLS secure channel"
+[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12
+
+function Install-Python {
+    Param(
+        [string]$PythonVersion,
+        [string]$PythonInstaller,
+        [string]$PythonInstallPath,
+        [string]$PythonInstallerHash
+    )
+    $PythonInstallerUrl = "https://www.python.org/ftp/python/$PythonVersion/$PythonInstaller.exe"
+    $PythonInstallerPath = "C:\tools\$PythonInstaller.exe"
+
+    # Downloads installer
+    Write-Host "Downloading the Python installer: $PythonInstallerUrl => $PythonInstallerPath"
+    Invoke-WebRequest -Uri $PythonInstallerUrl -OutFile $PythonInstallerPath
+
+    # Validates checksum
+    $HashFromDownload = Get-FileHash -Path $PythonInstallerPath -Algorithm MD5
+    if ($HashFromDownload.Hash -ne $PythonInstallerHash) {
+        throw "Invalid Python installer: failed checksum!"
+    }
+    Write-Host "Python installer $PythonInstallerPath validated."
+
+    # Installs Python
+    & $PythonInstallerPath /passive InstallAllUsers=1 PrependPath=1 Include_test=0 TargetDir=$PythonInstallPath
+    if (-Not $?) {
+        throw "The Python installation exited with error!"
+    }
+
+    # NOTE(lidiz) Even if the install command finishes in the script, that
+    # doesn't mean the Python installation is finished. If using "ps" to check
+    # for running processes, you might see ongoing installers at this point.
+    # So, we needs this "hack" to reliably validate that the Python binary is
+    # functioning properly.
+
+    # Wait for the installer process
+    Wait-Process -Name $PythonInstaller -Timeout 300
+    Write-Host "Installation process exits normally."
+
+    # Validate Python binary
+    $PythonBinary = "$PythonInstallPath\python.exe"
+    & $PythonBinary -c 'print(42)'
+    Write-Host "Python binary works properly."
+
+    # Installs pip
+    & $PythonBinary -m ensurepip --user
+
+    Write-Host "Python $PythonVersion installed by $PythonInstaller at $PythonInstallPath."
+}
+
+# Python 3.8
+$Python38x86Config = @{
+    PythonVersion = "3.8.0"
+    PythonInstaller = "python-3.8.0"
+    PythonInstallPath = "C:\python38_32bit"
+    PythonInstallerHash = "412a649d36626d33b8ca5593cf18318c"
+}
+Install-Python @Python38x86Config
+
+$Python38x64Config = @{
+    PythonVersion = "3.8.0"
+    PythonInstaller = "python-3.8.0-amd64"
+    PythonInstallPath = "C:\python38"
+    PythonInstallerHash = "29ea87f24c32f5e924b7d63f8a08ee8d"
+}
+Install-Python @Python38x64Config
+
+# Python 3.9
+$Python39x86Config = @{
+    PythonVersion = "3.9.0"
+    PythonInstaller = "python-3.9.0"
+    PythonInstallPath = "C:\python39_32bit"
+    PythonInstallerHash = "4a2812db8ab9f2e522c96c7728cfcccb"
+}
+Install-Python @Python39x86Config
+
+$Python39x64Config = @{
+    PythonVersion = "3.9.0"
+    PythonInstaller = "python-3.9.0-amd64"
+    PythonInstallPath = "C:\python39"
+    PythonInstallerHash = "b61a33dc28f13b561452f3089c87eb63"
+}
+Install-Python @Python39x64Config

python/setup.py

@@ -16,6 +16,7 @@ import platform
 # namespace_packages option for the "google" package.
 from setuptools import setup, Extension, find_packages
 
+from distutils.command.build_ext import build_ext as _build_ext
 from distutils.command.build_py import build_py as _build_py
 from distutils.command.clean import clean as _clean
 from distutils.spawn import find_executable
@@ -156,6 +157,20 @@ class build_py(_build_py):
     return [(pkg, mod, fil) for (pkg, mod, fil) in modules
             if not any(fnmatch.fnmatchcase(fil, pat=pat) for pat in exclude)]
 
+class build_ext(_build_ext):
+  def get_ext_filename(self, ext_name):
+      # since python3.5, python extensions' shared libraries use a suffix that corresponds to the value
+      # of sysconfig.get_config_var('EXT_SUFFIX') and contains info about the architecture the library targets.
+      # E.g. on x64 linux the suffix is ".cpython-XYZ-x86_64-linux-gnu.so"
+      # When crosscompiling python wheels, we need to be able to override this suffix
+      # so that the resulting file name matches the target architecture and we end up with a well-formed
+      # wheel.
+      filename = _build_ext.get_ext_filename(self, ext_name)
+      orig_ext_suffix = sysconfig.get_config_var("EXT_SUFFIX")
+      new_ext_suffix = os.getenv("PROTOCOL_BUFFERS_OVERRIDE_EXT_SUFFIX")
+      if new_ext_suffix and filename.endswith(orig_ext_suffix):
+        filename = filename[:-len(orig_ext_suffix)] + new_ext_suffix
+      return filename
 
 class test_conformance(_build_py):
   target = 'test_python'
@@ -291,6 +306,7 @@ if __name__ == '__main__':
       cmdclass={
           'clean': clean,
           'build_py': build_py,
+          'build_ext': build_ext,
           'test_conformance': test_conformance,
       },
       install_requires=install_requires,