gh-126944: Show explicit errors when required arguments of pdb commands are missing (#130240)

Lib/pdb.py

@@ -1286,6 +1286,9 @@ class Pdb(bdb.Bdb, cmd.Cmd):
         Enables the breakpoints given as a space separated list of
         breakpoint numbers.
         """
+        if not arg:
+            self._print_invalid_arg(arg)
+            return
         args = arg.split()
         for i in args:
             try:
@@ -1307,6 +1310,9 @@ class Pdb(bdb.Bdb, cmd.Cmd):
         breakpoint, it remains in the list of breakpoints and can be
         (re-)enabled.
         """
+        if not arg:
+            self._print_invalid_arg(arg)
+            return
         args = arg.split()
         for i in args:
             try:
@@ -1327,6 +1333,9 @@ class Pdb(bdb.Bdb, cmd.Cmd):
         condition is absent, any existing condition is removed; i.e.,
         the breakpoint is made unconditional.
         """
+        if not arg:
+            self._print_invalid_arg(arg)
+            return
         args = arg.split(' ', 1)
         try:
             cond = args[1]
@@ -1360,6 +1369,9 @@ class Pdb(bdb.Bdb, cmd.Cmd):
         and the breakpoint is not disabled and any associated
         condition evaluates to true.
         """
+        if not arg:
+            self._print_invalid_arg(arg)
+            return
         args = arg.split()
         if not args:
             self.error('Breakpoint number expected')
@@ -1690,6 +1702,9 @@ class Pdb(bdb.Bdb, cmd.Cmd):
         instance it is not possible to jump into the middle of a
         for loop or out of a finally clause.
         """
+        if not arg:
+            self._print_invalid_arg(arg)
+            return
         if self.curindex + 1 != len(self.stack):
             self.error('You can only jump within the bottom frame')
             return
@@ -1715,6 +1730,9 @@ class Pdb(bdb.Bdb, cmd.Cmd):
         argument (which is an arbitrary expression or statement to be
         executed in the current environment).
         """
+        if not arg:
+            self._print_invalid_arg(arg)
+            return
         sys.settrace(None)
         globals = self.curframe.f_globals
         locals = self.curframe.f_locals
@@ -1840,6 +1858,9 @@ class Pdb(bdb.Bdb, cmd.Cmd):
 
         Print the value of the expression.
         """
+        if not arg:
+            self._print_invalid_arg(arg)
+            return
         self._msg_val_func(arg, repr)
 
     def do_pp(self, arg):
@@ -1847,6 +1868,9 @@ class Pdb(bdb.Bdb, cmd.Cmd):
 
         Pretty-print the value of the expression.
         """
+        if not arg:
+            self._print_invalid_arg(arg)
+            return
         self._msg_val_func(arg, pprint.pformat)
 
     complete_print = _complete_expression
@@ -1935,6 +1959,9 @@ class Pdb(bdb.Bdb, cmd.Cmd):
 
         Try to get source code for the given object and display it.
         """
+        if not arg:
+            self._print_invalid_arg(arg)
+            return
         try:
             obj = self._getval(arg)
         except:
@@ -1974,6 +2001,9 @@ class Pdb(bdb.Bdb, cmd.Cmd):
 
         Print the type of the argument.
         """
+        if not arg:
+            self._print_invalid_arg(arg)
+            return
         try:
             value = self._getval(arg)
         except:
@@ -2318,7 +2348,10 @@ class Pdb(bdb.Bdb, cmd.Cmd):
     def _print_invalid_arg(self, arg):
         """Return the usage string for a function."""
 
-        self.error(f"Invalid argument: {arg}")
+        if not arg:
+            self.error("Argument is required for this command")
+        else:
+            self.error(f"Invalid argument: {arg}")
 
         # Yes it's a bit hacky. Get the caller name, get the method based on
         # that name, and get the docstring from that method.

Lib/test/test_pdb.py

@@ -1758,10 +1758,12 @@ def test_pdb_invalid_arg():
     >>> def test_function():
     ...     import pdb; pdb.Pdb(nosigint=True, readrc=False).set_trace()
 
-    >>> with PdbTestInput([
+    >>> with PdbTestInput([  # doctest: +NORMALIZE_WHITESPACE
     ...     'a = 3',
     ...     'll 4',
     ...     'step 1',
+    ...     'p',
+    ...     'enable ',
     ...     'continue'
     ... ]):
     ...     test_function()
@@ -1776,6 +1778,12 @@ def test_pdb_invalid_arg():
     (Pdb) step 1
     *** Invalid argument: 1
           Usage: s(tep)
+    (Pdb) p
+    *** Argument is required for this command
+          Usage: p expression
+    (Pdb) enable
+    *** Argument is required for this command
+          Usage: enable bpnumber [bpnumber ...]
     (Pdb) continue
     """
 

Misc/NEWS.d/next/Library/2025-02-17-21-01-25.gh-issue-126944.49YTHZ.rst

@@ -0,0 +1 @@
+Show explicit errors when required arguments of :mod:`pdb` commands are missing