Don't pass the realpath of script target to system functions

Author: johnslavik

Lib/pdb.py

@@ -183,13 +183,17 @@ class _ExecutableTarget:
 
 class _ScriptTarget(_ExecutableTarget):
     def __init__(self, target):
-        self._target = os.path.realpath(target)
-
-        if not os.path.exists(self._target):
-            print(f'Error: {target} does not exist')
+        self._orig_target = target
+        self._target = os.path.realpath(self._orig_target)
+
+        # Do not pass realpath to system functions, because it breaks
+        # pseudofiles such as anonymous pipe symlinks from process substitution.
+        # See GH-142315 for more details.
+        if not os.path.exists(self._orig_target):
+            print(f'Error: {self._orig_target} does not exist')
             sys.exit(1)
-        if os.path.isdir(self._target):
-            print(f'Error: {target} is a directory')
+        if os.path.isdir(self._orig_target):
+            print(f'Error: {self._orig_target} is a directory')
             sys.exit(1)
 
         # If safe_path(-P) is not set, sys.path[0] is the directory
@@ -207,8 +211,8 @@ def filename(self):
     @property
     def code(self):
         # Open the file each time because the file may be modified
-        with io.open_code(self._target) as fp:
-            return f"exec(compile({fp.read()!r}, {self._target!r}, 'exec'))"
+        with io.open_code(self._orig_target) as fp:
+            return f"exec(compile({fp.read()!r}, {self._orig_target!r}, 'exec'))"
 
     @property
     def namespace(self):

Misc/NEWS.d/next/Library/2025-12-07-02-36-24.gh-issue-142315.02o5E_.rst

@@ -0,0 +1 @@
+Pdb can run scripts from pseudofiles. Patch by Bartosz Sławecki.