[Python-checkins] gh-95359: Fix py.exe launcher handling of per-user py.ini and command names (GH-95399)

[miss-islington]

https://github.com/python/cpython/commit/1368a1f724ebcab803644adbf764d8d30b18cfd0
commit: 1368a1f724ebcab803644adbf764d8d30b18cfd0
branch: 3.11
author: Miss Islington (bot) <31488909+miss-islington at users.noreply.github.com>
committer: miss-islington <31488909+miss-islington at users.noreply.github.com>
date: 2022-07-28T13:52:13-07:00
summary:

gh-95359: Fix py.exe launcher handling of per-user py.ini and command names (GH-95399)

(cherry picked from commit 38bb2068fe1f51a74b36c46e820abc5f6422cded)

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

files:
A Misc/NEWS.d/next/Windows/2022-07-28-20-21-38.gh-issue-95359.ywMrgu.rst
M Lib/test/test_launcher.py
M PC/launcher2.c

diff --git a/Lib/test/test_launcher.py b/Lib/test/test_launcher.py
index 0b7cbaad3f582..e47078dc9f7bd 100644
--- a/Lib/test/test_launcher.py
+++ b/Lib/test/test_launcher.py
@@ -70,7 +70,7 @@
 
 TEST_PY_COMMANDS = "\n".join([
     "[defaults]",
-    *[f"{k.lower()}={v}" for k, v in TEST_PY_ENV.items()]
+    *[f"{k[3:].lower()}={v}" for k, v in TEST_PY_ENV.items()]
 ])
 
 
diff --git a/Misc/NEWS.d/next/Windows/2022-07-28-20-21-38.gh-issue-95359.ywMrgu.rst b/Misc/NEWS.d/next/Windows/2022-07-28-20-21-38.gh-issue-95359.ywMrgu.rst
new file mode 100644
index 0000000000000..513a2be28a9c2
--- /dev/null
+++ b/Misc/NEWS.d/next/Windows/2022-07-28-20-21-38.gh-issue-95359.ywMrgu.rst
@@ -0,0 +1,3 @@
+Fix :ref:`launcher` handling of :file:`py.ini` commands (it was incorrectly
+expecting a ``py_`` prefix on keys) and crashes when reading per-user
+configuration file.
diff --git a/PC/launcher2.c b/PC/launcher2.c
index 31b5617771e9b..033218ee2f408 100644
--- a/PC/launcher2.c
+++ b/PC/launcher2.c
@@ -761,7 +761,7 @@ _readIni(const wchar_t *section, const wchar_t *settingName, wchar_t *buffer, in
         n = GetPrivateProfileStringW(section, settingName, NULL, buffer, bufferLength, iniPath);
         if (n) {
             debug(L"# Found %s in %s\n", settingName, iniPath);
-            return true;
+            return n;
         } else if (GetLastError() == ERROR_FILE_NOT_FOUND) {
             debug(L"# Did not find file %s\n", iniPath);
         } else {
@@ -946,13 +946,17 @@ checkDefaults(SearchInfo *search)
 
     // If tag is only a major version number, expand it from the environment
     // or an ini file
-    const wchar_t *settingName = NULL;
+    const wchar_t *iniSettingName = NULL;
+    const wchar_t *envSettingName = NULL;
     if (!search->tag || !search->tagLength) {
-        settingName = L"py_python";
+        iniSettingName = L"python";
+        envSettingName = L"py_python";
     } else if (0 == wcsncmp(search->tag, L"3", search->tagLength)) {
-        settingName = L"py_python3";
+        iniSettingName = L"python3";
+        envSettingName = L"py_python3";
     } else if (0 == wcsncmp(search->tag, L"2", search->tagLength)) {
-        settingName = L"py_python2";
+        iniSettingName = L"python2";
+        envSettingName = L"py_python2";
     } else {
         debug(L"# Cannot select defaults for tag '%.*s'\n", search->tagLength, search->tag);
         return 0;
@@ -960,11 +964,11 @@ checkDefaults(SearchInfo *search)
 
     // First, try to read an environment variable
     wchar_t buffer[MAXLEN];
-    int n = GetEnvironmentVariableW(settingName, buffer, MAXLEN);
+    int n = GetEnvironmentVariableW(envSettingName, buffer, MAXLEN);
 
     // If none found, check in our two .ini files instead
     if (!n) {
-        n = _readIni(L"defaults", settingName, buffer, MAXLEN);
+        n = _readIni(L"defaults", iniSettingName, buffer, MAXLEN);
     }
 
     if (n) {