gh-96559: Fixes Windows launcher handling of defaults using old-style tags, and adds What's New section (GH-96595)

(cherry picked from commit 80a9bd2e94)

Co-authored-by: Steve Dower <steve.dower@python.org>

Doc/whatsnew/3.11.rst

@@ -352,6 +352,28 @@ PEP 563 May Not Be the Future
   that was planned for this release has been indefinitely postponed.
   See `this message <https://mail.python.org/archives/list/python-dev@python.org/message/VIZEBX5EYMSYIJNDBF6DMUMZOCWHARSO/>`_ for more information.
 
+Windows py.exe launcher improvements
+------------------------------------
+
+The copy of :ref:`launcher` included with Python 3.11 has been significantly
+updated. It now supports company/tag syntax as defined in :pep:`514` using the
+``-V:<company>/<tag>`` argument instead of the limited ``-x.y`` argument. This
+allows launching distributions other than ``PythonCore``, which is the one
+obtained from `python.org <https://python.org>`_.
+
+When using ``-V:`` selectors, either company or tag can be omitted, but all
+installs will be searched. For example, ``-V:OtherPython/`` will select the
+"best" tag registered for ``OtherPython``, while ``-V:3.11`` or ``-V:/3.11``
+will select the "best" distribution with tag ``3.11``.
+
+When using legacy ``-x``, ``-x.y``, ``-x-ZZ`` or ``-x.y-ZZ`` arguments, all
+existing behaviour should be preserved from past versions. Only releases from
+``PythonCore`` will be selected. However, the ``-64`` suffix now implies "not
+32-bit", as there are multiple supported 64-bit platforms. 32-bit runtimes are
+detected by checking its tag for a ``-32`` suffix. All releases of Python
+since 3.5 have included this in their 32-bit builds.
+
+
 Other Language Changes
 ======================
 

Lib/test/test_launcher.py

@@ -559,6 +559,13 @@ class TestLauncher(unittest.TestCase, RunPyMixin):
         self.assertEqual("3.100", data["SearchInfo.tag"])
         self.assertEqual(f'X.Y.exe -prearg "{script}" -postarg', data["stdout"].strip())
 
+    def test_py_handle_64_in_ini(self):
+        with self.py_ini("\n".join(["[defaults]", "python=3.999-64"])):
+            # Expect this to fail, but should get oldStyleTag flipped on
+            data = self.run_py([], allow_fail=True, expect_returncode=103)
+        self.assertEqual("3.999-64", data["SearchInfo.tag"])
+        self.assertEqual("True", data["SearchInfo.oldStyleTag"])
+
     def test_search_path(self):
         stem = Path(sys.executable).stem
         with self.py_ini(TEST_PY_COMMANDS):

Misc/NEWS.d/next/Windows/2022-09-05-18-32-47.gh-issue-96559.561sUd.rst

@@ -0,0 +1,3 @@
+Fixes the Windows launcher not using the compatible interpretation of
+default tags found in configuration files when no tag was passed to the
+command.

PC/launcher2.c

@@ -393,12 +393,6 @@ typedef struct {
     // only currently possible high priority environment is an active virtual
     // environment
     bool lowPriorityTag;
-    // if true, we had an old-style tag with '-64' suffix, and so do not
-    // want to match tags like '3.x-32'
-    bool exclude32Bit;
-    // if true, we had an old-style tag with '-32' suffix, and so *only*
-    // want to match tags like '3.x-32'
-    bool only32Bit;
     // if true, allow PEP 514 lookup to override 'executable'
     bool allowExecutableOverride;
     // if true, allow a nearby pyvenv.cfg to locate the executable
@@ -483,8 +477,6 @@ dumpSearchInfo(SearchInfo *search)
     DEBUG_2(tag, tagLength);
     DEBUG_BOOL(oldStyleTag);
     DEBUG_BOOL(lowPriorityTag);
-    DEBUG_BOOL(exclude32Bit);
-    DEBUG_BOOL(only32Bit);
     DEBUG_BOOL(allowDefaults);
     DEBUG_BOOL(allowExecutableOverride);
     DEBUG_BOOL(windowed);
@@ -649,17 +641,6 @@ parseCommandLine(SearchInfo *search)
                 search->tagLength = argLen;
                 search->oldStyleTag = true;
                 search->restOfCmdLine = tail;
-                // If the tag ends with -64, we want to exclude 32-bit runtimes
-                // (If the tag ends with -32, it will be filtered later)
-                if (argLen > 3) {
-                    if (0 == _compareArgument(&arg[argLen - 3], 3, L"-64", 3)) {
-                        search->tagLength -= 3;
-                        search->exclude32Bit = true;
-                    } else if (0 == _compareArgument(&arg[argLen - 3], 3, L"-32", 3)) {
-                        search->tagLength -= 3;
-                        search->only32Bit = true;
-                    }
-                }
             } else if (STARTSWITH(L"V:") || STARTSWITH(L"-version:")) {
                 // Arguments starting with 'V:' specify company and/or tag
                 const wchar_t *argStart = wcschr(arg, L':') + 1;
@@ -1087,6 +1068,7 @@ checkDefaults(SearchInfo *search)
         if (!slash) {
             search->tag = tag;
             search->tagLength = n;
+            search->oldStyleTag = true;
         } else {
             search->company = tag;
             search->companyLength = (int)(slash - tag);
@@ -1966,10 +1948,25 @@ _selectEnvironment(const SearchInfo *search, EnvironmentInfo *env, EnvironmentIn
             }
         } else if (0 == _compare(env->company, -1, L"PythonCore", -1)) {
             // Old-style tags can only match PythonCore entries
-            if (_startsWith(env->tag, -1, search->tag, search->tagLength)) {
+
-                if (search->exclude32Bit && _is32Bit(env)) {
+            // If the tag ends with -64, we want to exclude 32-bit runtimes
+            // (If the tag ends with -32, it will be filtered later)
+            int tagLength = search->tagLength;
+            bool exclude32Bit = false, only32Bit = false;
+            if (tagLength > 3) {
+                if (0 == _compareArgument(&search->tag[tagLength - 3], 3, L"-64", 3)) {
+                    tagLength -= 3;
+                    exclude32Bit = true;
+                } else if (0 == _compareArgument(&search->tag[tagLength - 3], 3, L"-32", 3)) {
+                    tagLength -= 3;
+                    only32Bit = true;
+                }
+            }
+
+            if (_startsWith(env->tag, -1, search->tag, tagLength)) {
+                if (exclude32Bit && _is32Bit(env)) {
                     debug(L"# Excluding %s/%s because it looks like 32bit\n", env->company, env->tag);
-                } else if (search->only32Bit && !_is32Bit(env)) {
+                } else if (only32Bit && !_is32Bit(env)) {
                     debug(L"# Excluding %s/%s because it doesn't look 32bit\n", env->company, env->tag);
                 } else {
                     *best = env;