Issue #19456: ntpath.join() now joins relative paths correctly when a drive

is present.

1 files changed, 24 insertions, 55 deletions

diff --git a/Lib/ntpath.py b/Lib/ntpath.py
index f3b3111..fc9463c 100644
--- a/Lib/ntpath.py
+++ b/Lib/ntpath.py
@@ -59,61 +59,30 @@ def isabs(s):
 
 
 # Join two (or more) paths.
-
-def join(a, *p):
-    """Join two or more pathname components, inserting "\\" as needed.
-    If any component is an absolute path, all previous path components
-    will be discarded."""
-    path = a
-    for b in p:
-        b_wins = 0  # set to 1 iff b makes path irrelevant
-        if path == "":
-            b_wins = 1
-
-        elif isabs(b):
-            # This probably wipes out path so far.  However, it's more
-            # complicated if path begins with a drive letter:
-            #     1. join('c:', '/a') == 'c:/a'
-            #     2. join('c:/', '/a') == 'c:/a'
-            # But
-            #     3. join('c:/a', '/b') == '/b'
-            #     4. join('c:', 'd:/') = 'd:/'
-            #     5. join('c:/', 'd:/') = 'd:/'
-            if path[1:2] != ":" or b[1:2] == ":":
-                # Path doesn't start with a drive letter, or cases 4 and 5.
-                b_wins = 1
-
-            # Else path has a drive letter, and b doesn't but is absolute.
-            elif len(path) > 3 or (len(path) == 3 and
-                                   path[-1] not in "/\\"):
-                # case 3
-                b_wins = 1
-
-        if b_wins:
-            path = b
-        else:
-            # Join, and ensure there's a separator.
-            assert len(path) > 0
-            if path[-1] in "/\\":
-                if b and b[0] in "/\\":
-                    path += b[1:]
-                else:
-                    path += b
-            elif path[-1] == ":":
-                path += b
-            elif b:
-                if b[0] in "/\\":
-                    path += b
-                else:
-                    path += "\\" + b
-            else:
-                # path is not empty and does not end with a backslash,
-                # but b is empty; since, e.g., split('a/') produces
-                # ('a', ''), it's best if join() adds a backslash in
-                # this case.
-                path += '\\'
-
-    return path
+def join(path, *paths):
+    """Join two or more pathname components, inserting "\\" as needed."""
+    result_drive, result_path = splitdrive(path)
+    for p in paths:
+        p_drive, p_path = splitdrive(p)
+        if p_path and p_path[0] in '\\/':
+            # Second path is absolute
+            if p_drive or not result_drive:
+                result_drive = p_drive
+            result_path = p_path
+            continue
+        elif p_drive and p_drive != result_drive:
+            if p_drive.lower() != result_drive.lower():
+                # Different drives => ignore the first path entirely
+                result_drive = p_drive
+                result_path = p_path
+                continue
+            # Same drive in different case
+            result_drive = p_drive
+        # Second path is relative to the first
+        if result_path and result_path[-1] not in '\\/':
+            result_path = result_path + '\\'
+        result_path = result_path + p_path
+    return result_drive + result_path
 
 
 # Split a path in a drive specification (a drive letter followed by a