gh-126782: Support qualified referencing for ntpath.abspath()

Include/internal/pycore_fileutils.h

@@ -279,7 +279,8 @@ extern size_t _Py_find_basename(const wchar_t *filename);
 // Export for '_testinternalcapi' shared extension
 PyAPI_FUNC(wchar_t*) _Py_normpath(wchar_t *path, Py_ssize_t size);
 
-extern wchar_t *_Py_normpath_and_size(wchar_t *path, Py_ssize_t size, Py_ssize_t *length);
+extern wchar_t *_Py_normpath_and_size(wchar_t *path, Py_ssize_t size, Py_ssize_t *length,
+                                      int explicit_curdir);
 
 // The Windows Games API family does not provide these functions
 // so provide our own implementations. Remove them in case they get added

Include/internal/pycore_global_strings.h

@@ -413,6 +413,7 @@ struct _Py_global_strings {
         STRUCT_FOR_ID(exception)
         STRUCT_FOR_ID(existing_file_name)
         STRUCT_FOR_ID(exp)
+        STRUCT_FOR_ID(explicit_curdir)
         STRUCT_FOR_ID(extend)
         STRUCT_FOR_ID(extra_tokens)
         STRUCT_FOR_ID(facility)

Lib/ntpath.py

@@ -555,6 +555,7 @@ def normpath(path):
 
 # Return an absolute path.
 try:
+    from nt import _path_normpath_ex as _normpath
     from nt import _getfullpathname
 
 except ImportError: # not running on Windows - mock up something sensible
@@ -573,7 +574,7 @@ def abspath(path):
     def abspath(path):
         """Return the absolute version of a path."""
         try:
-            return _getfullpathname(normpath(path))
+            return _getfullpathname(_normpath(path, explicit_curdir=True))
         except (OSError, ValueError):
             # See gh-75230, handle outside for cleaner traceback
             pass

Lib/test/test_ntpath.py

@@ -839,6 +839,20 @@ def test_abspath(self):
             tester('ntpath.abspath("")', cwd_dir)
             tester('ntpath.abspath(" ")', cwd_dir + "\\ ")
             tester('ntpath.abspath("?")', cwd_dir + "\\?")
+            tester('ntpath.abspath("con")', r"\\.\con")
+            # bpo-45354: Windows 11 changed MS-DOS device name handling
+            if sys.getwindowsversion()[:3] < (10, 0, 22000):
+                tester('ntpath.abspath("./con")', r"\\.\con")
+                tester('ntpath.abspath("foo/../con")', r"\\.\con")
+                tester('ntpath.abspath("con/foo/..")', r"\\.\con")
+                tester('ntpath.abspath("con/.")', r"\\.\con")
+            else:
+                tester('ntpath.abspath("./con")', cwd_dir + r"\con")
+                tester('ntpath.abspath("foo/../con")', cwd_dir + r"\con")
+                tester('ntpath.abspath("con/foo/..")', cwd_dir + r"\con")
+                tester('ntpath.abspath("con/.")', cwd_dir + r"\con")
+            tester('ntpath.abspath("./Z:spam")', cwd_dir + r"\Z:spam")
+            tester('ntpath.abspath("spam/../Z:eggs")', cwd_dir + r"\Z:eggs")
             drive, _ = ntpath.splitdrive(cwd_dir)
             tester('ntpath.abspath("/abc/")', drive + "\\abc")
 

Misc/NEWS.d/next/Library/2024-05-31-12-44-38.gh-issue-126782.Atm9ol.rst

@@ -0,0 +1 @@
+Support qualified referencing for :func:`os.path.abspath` on Windows.

Modules/posixmodule.c

@@ -5594,21 +5594,25 @@ os__path_splitroot_ex_impl(PyObject *module, path_t *path)
 
 
 /*[clinic input]
-os._path_normpath
+os._path_normpath_ex
 
     path: path_t(make_wide=True, nonstrict=True)
+    *
+    explicit_curdir: bool = False
 
 Normalize path, eliminating double slashes, etc.
 [clinic start generated code]*/
 
 static PyObject *
-os__path_normpath_impl(PyObject *module, path_t *path)
-/*[clinic end generated code: output=d353e7ed9410c044 input=3d4ac23b06332dcb]*/
+os__path_normpath_ex_impl(PyObject *module, path_t *path,
+                          int explicit_curdir)
+/*[clinic end generated code: output=4c4c3bf33a70fe57 input=90fe0dfc4b3a751b]*/
 {
     PyObject *result;
     Py_ssize_t norm_len;
     wchar_t *norm_path = _Py_normpath_and_size((wchar_t *)path->wide,
-                                               path->length, &norm_len);
+                                               path->length, &norm_len,
+                                               explicit_curdir);
     if (!norm_len) {
         result = PyUnicode_FromOrdinal('.');
     }
@@ -5621,6 +5625,23 @@ os__path_normpath_impl(PyObject *module, path_t *path)
     return result;
 }
 
+
+/*[clinic input]
+os._path_normpath
+
+    path: path_t(make_wide=True, nonstrict=True)
+
+Normalize path, eliminating double slashes, etc.
+[clinic start generated code]*/
+
+static PyObject *
+os__path_normpath_impl(PyObject *module, path_t *path)
+/*[clinic end generated code: output=d353e7ed9410c044 input=3d4ac23b06332dcb]*/
+{
+
+    return os__path_normpath_ex_impl(module, path, 0);
+}
+
 /*[clinic input]
 os.mkdir
 
@@ -17059,6 +17080,7 @@ static PyMethodDef posix_methods[] = {
     OS__GETVOLUMEPATHNAME_METHODDEF
     OS__PATH_SPLITROOT_METHODDEF
     OS__PATH_SPLITROOT_EX_METHODDEF
+    OS__PATH_NORMPATH_EX_METHODDEF
     OS__PATH_NORMPATH_METHODDEF
     OS_GETLOADAVG_METHODDEF
     OS_URANDOM_METHODDEF

Python/fileutils.c

@@ -2483,9 +2483,12 @@ _Py_find_basename(const wchar_t *filename)
    make the path longer, and will not fail. 'size' is the length of
    the path, if known. If -1, the first null character will be assumed
    to be the end of the path. 'normsize' will be set to contain the
-   length of the resulting normalized path. */
+   length of the resulting normalized path. If 'explicit_curdir' is
+   set, an explicit curdir will be used for qualified referencing in
+   the cwd. */
 wchar_t *
-_Py_normpath_and_size(wchar_t *path, Py_ssize_t size, Py_ssize_t *normsize)
+_Py_normpath_and_size(wchar_t *path, Py_ssize_t size, Py_ssize_t *normsize,
+                      int explicit_curdir)
 {
     assert(path != NULL);
     if ((size < 0 && !path[0]) || size == 0) {
@@ -2497,6 +2500,7 @@ _Py_normpath_and_size(wchar_t *path, Py_ssize_t size, Py_ssize_t *normsize)
     wchar_t *p2 = path;     // destination of a scanned character to be ljusted
     wchar_t *minP2 = path;  // the beginning of the destination range
     wchar_t lastC = L'\0';  // the last ljusted character, p2[-1] in most cases
+    int explicit = 0;       // uses qualified referencing in the cwd
 
 #define IS_END(x) (pEnd ? (x) == pEnd : !*(x))
 #ifdef ALTSEP
@@ -2506,38 +2510,36 @@ _Py_normpath_and_size(wchar_t *path, Py_ssize_t size, Py_ssize_t *normsize)
 #endif
 #define SEP_OR_END(x) (IS_SEP(x) || IS_END(x))
 
+    Py_ssize_t drvsize, rootsize;
+    _Py_skiproot(path, size, &drvsize, &rootsize);
     if (p1[0] == L'.' && IS_SEP(&p1[1])) {
         // Skip leading '.\'
-        path = &path[2];
-        while (IS_SEP(path)) {
-            path++;
+        p1 = &path[2];
+        while (IS_SEP(p1)) {
+            p1++;
         }
-        p1 = p2 = minP2 = path;
         lastC = SEP;
+        explicit = 1;
     }
-    else {
-        Py_ssize_t drvsize, rootsize;
-        _Py_skiproot(path, size, &drvsize, &rootsize);
-        if (drvsize || rootsize) {
-            // Skip past root and update minP2
-            p1 = &path[drvsize + rootsize];
+    else if (drvsize || rootsize) {
+        // Skip past root and update minP2
+        p1 = &path[drvsize + rootsize];
 #ifndef ALTSEP
-            p2 = p1;
+        p2 = p1;
 #else
-            for (; p2 < p1; ++p2) {
-                if (*p2 == ALTSEP) {
-                    *p2 = SEP;
-                }
+        for (; p2 < p1; ++p2) {
+            if (*p2 == ALTSEP) {
+                *p2 = SEP;
             }
+        }
 #endif
-            minP2 = p2 - 1;
-            lastC = *minP2;
+        minP2 = p2 - 1;
+        lastC = *minP2;
 #ifdef MS_WINDOWS
-            if (lastC != SEP) {
-                minP2++;
-            }
-#endif
+        if (lastC != SEP) {
+            minP2++;
         }
+#endif
     }
 
     /* if pEnd is specified, check that. Else, check for null terminator */
@@ -2569,9 +2571,11 @@ _Py_normpath_and_size(wchar_t *path, Py_ssize_t size, Py_ssize_t *normsize)
                         p2 = p3 + 1;
                     } else {
                         p2 = p3;
+                        explicit = 1;
                     }
                     p1 += 1;
                 } else if (sep_at_1) {
+                    explicit = 1;
                 } else {
                     *p2++ = lastC = c;
                 }
@@ -2591,6 +2595,31 @@ _Py_normpath_and_size(wchar_t *path, Py_ssize_t size, Py_ssize_t *normsize)
     } else {
         --p2;
     }
+    if (explicit_curdir && !rootsize && explicit) {
+        // Add explicit curdir
+        if (p2 == minP2 - 1) {
+            // Set to '.'
+            p2++;
+            assert(p2 < p1);
+            *p2 = L'.';
+        }
+        else if (minP2[0] != L'.' || minP2[1] != L'.' ||
+                 !SEP_OR_END(&minP2[2]))
+        {
+            // Add leading '.\'
+            wchar_t *p3 = p2;
+            p2 += 2;
+            assert(p2 < p1);
+            while (p3 != minP2) {
+                p3[2] = *p3;
+                p3--;
+            }
+            p3[2] = p3[0];
+            p3[1] = SEP;
+            p3[0] = L'.';
+        }
+        p2[1] = L'\0';
+    }
     *normsize = p2 - path + 1;
 #undef SEP_OR_END
 #undef IS_SEP
@@ -2607,7 +2636,7 @@ wchar_t *
 _Py_normpath(wchar_t *path, Py_ssize_t size)
 {
     Py_ssize_t norm_length;
-    return _Py_normpath_and_size(path, size, &norm_length);
+    return _Py_normpath_and_size(path, size, &norm_length, 0);
 }