commands command with no bpnumber should use last available breakpoint

Author: cocolato

Lib/pdb.py

@@ -1315,7 +1315,12 @@ def do_commands(self, arg):
         reached.
         """
         if not arg:
-            bnum = len(bdb.Breakpoint.bpbynumber) - 1
+            for bnum in range(len(bdb.Breakpoint.bpbynumber) - 1, -1, -1):
+                if bdb.Breakpoint.bpbynumber[bnum] is not None:
+                    break
+                if bnum == 0:
+                    self.error('no breakpoints setted')
+                    return
         else:
             try:
                 bnum = int(arg)

Lib/test/test_pdb.py

@@ -3478,6 +3478,43 @@ def test_pdb_issue_gh_65052():
     (Pdb) continue
     """
 
+def test_pdb_issue_142834():
+    """See issue-142834
+
+    >>> def test_function():
+    ...     import pdb; pdb.Pdb(nosigint=True, readrc=False).set_trace()
+    ...     foo = 1
+    ...     bar = 2
+
+    >>> with PdbTestInput([  # doctest: +NORMALIZE_WHITESPACE
+    ...     'break 4',
+    ...     'break 3',
+    ...     'clear 2',
+    ...     'commands',
+    ...     'p "success"',
+    ...     'end',
+    ...     'continue',
+    ...     '',
+    ... ]):
+    ...    test_function()
+    > <doctest test.test_pdb.test_pdb_issue_gh_xxx[0]>(2)test_function()
+    -> import pdb; pdb.Pdb(nosigint=True, readrc=False).set_trace()
+    (Pdb) break 4
+    Breakpoint 1 at <doctest test.test_pdb.test_pdb_issue_gh_xxx[0]>:4
+    (Pdb) break 3
+    Breakpoint 2 at <doctest test.test_pdb.test_pdb_issue_gh_xxx[0]>:3
+    (Pdb) clear 2
+    Deleted breakpoint 2 at <doctest test.test_pdb.test_pdb_issue_gh_xxx[0]>:3
+    (Pdb) commands
+    (com) p "success"
+    (com) end
+    (Pdb) continue
+    'success'
+    > <doctest test.test_pdb.test_pdb_issue_gh_xxx[0]>(4)test_function()
+    -> bar = 2
+    (Pdb)
+    """
+
 
 @support.force_not_colorized_test_class
 @support.requires_subprocess()