[python3] Do not ensurepip. Provide venv instructions. (#24906)

* [python3] Bootstrap pip with ${CURRENT_INSTALLED_DIR}

* [python3] Disable ensurepip -- add venv usage instructions

Co-authored-by: Max Khon <fjoe@samodelkin.net>

ports/python3/0010-ensurepip.patch

@@ -0,0 +1,11 @@
+--- a/Lib/ensurepip/__init__.py	2021-10-05 00:40:46.000000000 +0700
++++ b/Lib/ensurepip/__init__.py	2022-01-11 15:22:54.001498300 +0700
+@@ -86,6 +86,8 @@
+     code = f"""
+ import runpy
+ import sys
++import os
++sys.executable = os.path.dirname(os.path.realpath(__file__))
+ sys.path = {additional_paths or []} + sys.path
+ sys.argv[1:] = {args}
+ runpy.run_module("pip", run_name="__main__", alter_sys=True)

ports/python3/portfile.cmake

@@ -29,8 +29,9 @@ elseif(VCPKG_TARGET_IS_WINDOWS AND CMAKE_SYSTEM_VERSION EQUAL 6.1)
     message(FATAL_ERROR "python3 requires the feature deprecated-win7-support when building on Windows 7.")
 endif()
 
-# The Windows 11 SDK has a problem that causes it to error on the resource files, so we patch that.
 if(VCPKG_TARGET_IS_WINDOWS OR VCPKG_TARGET_IS_UWP)
+    string(COMPARE EQUAL "${VCPKG_LIBRARY_LINKAGE}" "dynamic" PYTHON_ALLOW_EXTENSIONS)
+    # The Windows 11 SDK has a problem that causes it to error on the resource files, so we patch that.
     vcpkg_get_windows_sdk(WINSDK_VERSION)
     if("${WINSDK_VERSION}" VERSION_GREATER_EQUAL "10.0.22000")
         list(APPEND PATCHES "0007-workaround-windows-11-sdk-rc-compiler-error.patch")
@@ -70,7 +71,6 @@ endfunction()
 if(VCPKG_TARGET_IS_WINDOWS OR VCPKG_TARGET_IS_UWP)
     # Due to the way Python handles C extension modules on Windows, a static python core cannot
     # load extension modules.
-    string(COMPARE EQUAL ${VCPKG_LIBRARY_LINKAGE} "dynamic" PYTHON_ALLOW_EXTENSIONS)
     if(PYTHON_ALLOW_EXTENSIONS)
         find_library(BZ2_RELEASE NAMES bz2 PATHS "${CURRENT_INSTALLED_DIR}/lib" NO_DEFAULT_PATH)
         find_library(BZ2_DEBUG NAMES bz2d PATHS "${CURRENT_INSTALLED_DIR}/debug/lib" NO_DEFAULT_PATH)
@@ -171,15 +171,6 @@ if(VCPKG_TARGET_IS_WINDOWS OR VCPKG_TARGET_IS_UWP)
     file(GLOB PYTHON_INSTALLERS "${CURRENT_PACKAGES_DIR}/tools/${PORT}/wininst-*.exe")
     file(REMOVE ${PYTHON_LIBS} ${PYTHON_INSTALLERS})
 
-    # The generated python executable must match the host arch
-    if(PYTHON_ALLOW_EXTENSIONS AND NOT VCPKG_CROSSCOMPILING)
-        message(STATUS "Bootstrapping pip")
-        vcpkg_execute_required_process(COMMAND python -m ensurepip
-            WORKING_DIRECTORY "${CURRENT_PACKAGES_DIR}/tools/${PORT}"
-            LOGNAME "ensurepip-${TARGET_TRIPLET}"
-        )
-    endif()
-
     # pkg-config files
     if(NOT DEFINED VCPKG_BUILD_TYPE OR VCPKG_BUILD_TYPE STREQUAL "release")
         make_python_pkgconfig(FILE python.pc INSTALL_ROOT ${CURRENT_PACKAGES_DIR}
@@ -215,7 +206,7 @@ if(VCPKG_TARGET_IS_WINDOWS OR VCPKG_TARGET_IS_UWP)
 else()
     set(OPTIONS
         "--with-openssl=${CURRENT_INSTALLED_DIR}"
-        "--with-ensurepip"
+        "--without-ensurepip"
         "--with-suffix="
         "--with-system-expat"
         "--without-readline"
@@ -255,7 +246,17 @@ else()
     vcpkg_fixup_pkgconfig()
 endif()
 
-file(INSTALL "${CMAKE_CURRENT_LIST_DIR}/usage" DESTINATION "${CURRENT_PACKAGES_DIR}/share/${PORT}")
+file(READ "${CMAKE_CURRENT_LIST_DIR}/usage" usage)
+if(VCPKG_TARGET_IS_WINDOWS)
+    if(PYTHON_ALLOW_EXTENSIONS)
+        file(READ "${CMAKE_CURRENT_LIST_DIR}/usage.win" usage_extra)
+    else()
+        set(usage_extra "")
+    endif()
+else()
+    file(READ "${CMAKE_CURRENT_LIST_DIR}/usage.unix" usage_extra)
+endif()
+file(WRITE "${CURRENT_PACKAGES_DIR}/share/${PORT}/usage" "${usage}\n${usage_extra}")
 
 function(_generate_finder)
     cmake_parse_arguments(PythonFinder "NO_OVERRIDE" "DIRECTORY;PREFIX" "" ${ARGN})

ports/python3/usage.unix

@@ -0,0 +1,9 @@
+The package python3 provides a python interpreter that supports virtual environments:
+
+    $ tools/python3/python3.10 -m venv /path/to/venv
+    $ export VIRTUAL_ENV=/path/to/venv
+    $ export PATH=/path/to/venv/bin:$PATH
+    $ export -n PYTHONHOME
+    $ unset PYTHONHOME
+
+    See https://docs.python.org/3/library/venv.html for more details.

ports/python3/usage.win

@@ -0,0 +1,8 @@
+The package python3 provides a python interpreter that supports virtual environments:
+
+    >tools\python3\python3.10 -m venv c:\path\to\venv
+    >set VIRTUAL_ENV=c:\path\to\venv
+    >set PATH=c:\path\to\venv\bin;%PATH%
+    >set PYTHONHOME=
+
+    See https://docs.python.org/3/library/venv.html for more details.

ports/python3/vcpkg.json

@@ -1,7 +1,7 @@
 {
   "name": "python3",
   "version": "3.10.2",
-  "port-version": 1,
+  "port-version": 2,
   "description": "The Python programming language",
   "homepage": "https://github.com/python/cpython",
   "license": "Python-2.0",

versions/baseline.json

@@ -5658,7 +5658,7 @@
     },
     "python3": {
       "baseline": "3.10.2",
-      "port-version": 1
+      "port-version": 2
     },
     "qca": {
       "baseline": "2.3.4",

versions/p-/python3.json

@@ -1,5 +1,10 @@
 {
   "versions": [
+    {
+      "git-tree": "30321893b72abb4b682e3b66f75c54c1df3051c9",
+      "version": "3.10.2",
+      "port-version": 2
+    },
     {
       "git-tree": "4e348bd50d8c4252bda83903ce22f1e60d34be88",
       "version": "3.10.2",