gh-110944: Make pdb completion work for alias and convenience vars (GH-110945)

Lib/pdb.py

@@ -238,7 +238,7 @@ class Pdb(bdb.Bdb, cmd.Cmd):
         try:
             import readline
             # remove some common file name delimiters
-            readline.set_completer_delims(' \t\n`@#$%^&*()=+[{]}\\|;:\'",<>?')
+            readline.set_completer_delims(' \t\n`@#%^&*()=+[{]}\\|;:\'",<>?')
         except ImportError:
             pass
         self.allow_kbdint = False
@@ -686,6 +686,18 @@ class Pdb(bdb.Bdb, cmd.Cmd):
     # Generic completion functions.  Individual complete_foo methods can be
     # assigned below to one of these functions.
 
+    def completenames(self, text, line, begidx, endidx):
+        # Overwrite completenames() of cmd so for the command completion,
+        # if no current command matches, check for expressions as well
+        commands = super().completenames(text, line, begidx, endidx)
+        for alias in self.aliases:
+            if alias.startswith(text):
+                commands.append(alias)
+        if commands:
+            return commands
+        else:
+            return self._complete_expression(text, line, begidx, endidx)
+
     def _complete_location(self, text, line, begidx, endidx):
         # Complete a file/module/function location for break/tbreak/clear.
         if line.strip().endswith((':', ',')):
@@ -720,6 +732,10 @@ class Pdb(bdb.Bdb, cmd.Cmd):
         # complete builtins, and they clutter the namespace quite heavily, so we
         # leave them out.
         ns = {**self.curframe.f_globals, **self.curframe_locals}
+        if text.startswith("$"):
+            # Complete convenience variables
+            conv_vars = self.curframe.f_globals.get('__pdb_convenience_variables', {})
+            return [f"${name}" for name in conv_vars if name.startswith(text[1:])]
         if '.' in text:
             # Walk an attribute chain up to the last part, similar to what
             # rlcompleter does.  This will bail if any of the parts are not