gh-83180: Made launcher treat shebang 'python' tags as low priority so that active virtual environments are preferred (GH-108101)

1 files changed, 32 insertions, 6 deletions

diff --git a/PC/launcher2.c b/PC/launcher2.c
index bb500d4..116091f 100644
--- a/PC/launcher2.c
+++ b/PC/launcher2.c
@@ -195,6 +195,13 @@ join(wchar_t *buffer, size_t bufferLength, const wchar_t *fragment)
 }
 
 
+bool
+split_parent(wchar_t *buffer, size_t bufferLength)
+{
+    return SUCCEEDED(PathCchRemoveFileSpec(buffer, bufferLength));
+}
+
+
 int
 _compare(const wchar_t *x, int xLen, const wchar_t *y, int yLen)
 {
@@ -414,8 +421,8 @@ typedef struct {
     // if true, treats 'tag' as a non-PEP 514 filter
     bool oldStyleTag;
     // if true, ignores 'tag' when a high priority environment is found
-    // gh-92817: This is currently set when a tag is read from configuration or
-    // the environment, rather than the command line or a shebang line, and the
+    // gh-92817: This is currently set when a tag is read from configuration,
+    // the environment, or a shebang, rather than the command line, and the
     // only currently possible high priority environment is an active virtual
     // environment
     bool lowPriorityTag;
@@ -794,6 +801,8 @@ searchPath(SearchInfo *search, const wchar_t *shebang, int shebangLength)
         }
     }
 
+    debug(L"# Search PATH for %s\n", filename);
+
     wchar_t pathVariable[MAXLEN];
     int n = GetEnvironmentVariableW(L"PATH", pathVariable, MAXLEN);
     if (!n) {
@@ -1031,8 +1040,11 @@ checkShebang(SearchInfo *search)
     debug(L"Shebang: %s\n", shebang);
 
     // Handle shebangs that we should search PATH for
+    int executablePathWasSetByUsrBinEnv = 0;
     exitCode = searchPath(search, shebang, shebangLength);
-    if (exitCode != RC_NO_SHEBANG) {
+    if (exitCode == 0) {
+        executablePathWasSetByUsrBinEnv = 1;
+    } else if (exitCode != RC_NO_SHEBANG) {
         return exitCode;
     }
 
@@ -1067,7 +1079,7 @@ checkShebang(SearchInfo *search)
             search->tagLength = commandLength;
             // If we had 'python3.12.exe' then we want to strip the suffix
             // off of the tag
-            if (search->tagLength > 4) {
+            if (search->tagLength >= 4) {
                 const wchar_t *suffix = &search->tag[search->tagLength - 4];
                 if (0 == _comparePath(suffix, 4, L".exe", -1)) {
                     search->tagLength -= 4;
@@ -1075,13 +1087,14 @@ checkShebang(SearchInfo *search)
             }
             // If we had 'python3_d' then we want to strip the '_d' (any
             // '.exe' is already gone)
-            if (search->tagLength > 2) {
+            if (search->tagLength >= 2) {
                 const wchar_t *suffix = &search->tag[search->tagLength - 2];
                 if (0 == _comparePath(suffix, 2, L"_d", -1)) {
                     search->tagLength -= 2;
                 }
             }
             search->oldStyleTag = true;
+            search->lowPriorityTag = true;
             search->executableArgs = &command[commandLength];
             search->executableArgsLength = shebangLength - commandLength;
             if (search->tag && search->tagLength) {
@@ -1095,6 +1108,11 @@ checkShebang(SearchInfo *search)
         }
     }
 
+    // Didn't match a template, but we found it on PATH
+    if (executablePathWasSetByUsrBinEnv) {
+        return 0;
+    }
+
     // Unrecognised executables are first tried as command aliases
     commandLength = 0;
     while (commandLength < shebangLength && !isspace(shebang[commandLength])) {
@@ -1765,7 +1783,15 @@ virtualenvSearch(const SearchInfo *search, EnvironmentInfo **result)
         return 0;
     }
 
-    if (INVALID_FILE_ATTRIBUTES == GetFileAttributesW(buffer)) {
+    DWORD attr = GetFileAttributesW(buffer);
+    if (INVALID_FILE_ATTRIBUTES == attr && search->lowPriorityTag) {
+        if (!split_parent(buffer, MAXLEN) || !join(buffer, MAXLEN, L"python.exe")) {
+            return 0;
+        }
+        attr = GetFileAttributesW(buffer);
+    }
+
+    if (INVALID_FILE_ATTRIBUTES == attr) {
         debug(L"Python executable %s missing from virtual env\n", buffer);
         return 0;
     }