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gh-136057: Allow step and next to step over for loops #136160

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gh-136057: Allow step and next to step over for loops #136160

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24857e4
Allow step and next to step over for loops
gaogaotiantian Jul 1, 2025
83cd3b3
📜🤖 Added by blurb_it.
blurb-it[bot] Jul 1, 2025
e47731e
Update 2025-07-01-04-57-57.gh-issue-136057.4-t596.rst
gaogaotiantian Jul 1, 2025
99837fd
Deal with enterframe == None in set_step
gaogaotiantian Jul 1, 2025
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20 changes: 16 additions & 4 deletions Lib/bdb.py
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Original file line number Diff line number Diff line change
Expand Up @@ -306,7 +306,12 @@ def dispatch_line(self, frame):
self.user_line(). Raise BdbQuit if self.quitting is set.
Return self.trace_dispatch to continue tracing in this scope.
"""
if self.stop_here(frame) or self.break_here(frame):
# GH-136057
# For line events, besides whether we should stop at the frame, we
# also need to check if it's the same line as we issue the command.
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I don't think this is very clear: "it's the same line as we issue the command". I think you mean "the same frame and line at which the break command was issued by the user".

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It's not the break command, it's either next or step. But yes I'm open to all suggestions to make this clearer.

if (self.stop_here(frame) or self.break_here(frame)) and not (
self.startframe == frame and self.startlineno == frame.f_lineno
):
self.user_line(frame)
self.restart_events()
if self.quitting: raise BdbQuit
Expand Down Expand Up @@ -535,7 +540,8 @@ def _set_trace_opcodes(self, trace_opcodes):
if self.monitoring_tracer:
self.monitoring_tracer.update_local_events()

def _set_stopinfo(self, stopframe, returnframe, stoplineno=0, opcode=False):
def _set_stopinfo(self, stopframe, returnframe, stoplineno=0, opcode=False,
startframe=None, startlineno=None):
"""Set the attributes for stopping.
If stoplineno is greater than or equal to 0, then stop at line
Expand All @@ -548,6 +554,10 @@ def _set_stopinfo(self, stopframe, returnframe, stoplineno=0, opcode=False):
# stoplineno >= 0 means: stop at line >= the stoplineno
# stoplineno -1 means: don't stop at all
self.stoplineno = stoplineno
# startframe/startlineno is the frame/line number when the user does
# step or next. We don't want to stop at the same line for those commands.
self.startframe = startframe
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Maybe we could pick a more informative name, something like "command frame", because it's ambiguous here what exactly started at that frame.

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Yeah we can change it, but there's actually a caveat here - it's not really the command frame. You can do up to an upper frame and do next/step - the behavior is different. next will next to the line at the upper frame, so the frame we need is the "command frame". step however, will stop at the innermost frame, no matter which frame you are inspecting - that's just how step works.

So it's more like a "do not stop here again if it's a line event" frame/lineno. Do you think there's better name to describe it?

self.startlineno = startlineno
self._set_trace_opcodes(opcode)

def _set_caller_tracefunc(self, current_frame):
Expand All @@ -573,15 +583,17 @@ def set_until(self, frame, lineno=None):

def set_step(self):
"""Stop after one line of code."""
self._set_stopinfo(None, None)
# set_step() could be called from signal handler so enterframe might be None
self._set_stopinfo(None, None, startframe=self.enterframe,
startlineno=getattr(self.enterframe, 'f_lineno', None))

def set_stepinstr(self):
"""Stop before the next instruction."""
self._set_stopinfo(None, None, opcode=True)

def set_next(self, frame):
"""Stop on the next line in or below the given frame."""
self._set_stopinfo(frame, None)
self._set_stopinfo(frame, None, startframe=frame, startlineno=frame.f_lineno)

def set_return(self, frame):
"""Stop when returning from the given frame."""
Expand Down
31 changes: 31 additions & 0 deletions Lib/test/test_pdb.py
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Expand Up @@ -3232,6 +3232,37 @@ def test_pdb_issue_gh_127321():
"""


def test_pdb_issue_gh_136057():
"""See GH-136057
"step" and "next" commands should be able to get over list comprehensions
>>> def test_function():
... import pdb; pdb.Pdb(nosigint=True, readrc=False).set_trace()
... lst = [i for i in range(10)]
... for i in lst: pass

>>> with PdbTestInput([ # doctest: +NORMALIZE_WHITESPACE
... 'next',
... 'next',
... 'step',
... 'continue',
... ]):
... test_function()
> <doctest test.test_pdb.test_pdb_issue_gh_136057[0]>(2)test_function()
-> import pdb; pdb.Pdb(nosigint=True, readrc=False).set_trace()
(Pdb) next
> <doctest test.test_pdb.test_pdb_issue_gh_136057[0]>(3)test_function()
-> lst = [i for i in range(10)]
(Pdb) next
> <doctest test.test_pdb.test_pdb_issue_gh_136057[0]>(4)test_function()
-> for i in lst: pass
(Pdb) step
--Return--
> <doctest test.test_pdb.test_pdb_issue_gh_136057[0]>(4)test_function()->None
-> for i in lst: pass
(Pdb) continue
"""


def test_pdb_issue_gh_80731():
"""See GH-80731

Expand Down
1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Library/2025-07-01-04-57-57.gh-issue-136057.4-t596.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
Fixed the bug in :mod:`pdb` and :mod:`bdb` where ``next`` and ``step`` can't go over the line if a loop exists in the line.
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