[mlouielu]

watch and awatch will detect value change and breakout, rwatch using dis module to get the file bytecode, with the lineno it can detect current line is load (read) or not.

• Issue: bdb and pdb: Add watchpoint function #74614

[auvipy]

Please rebase

[github-actions]

This PR is stale because it has been open for 30 days with no activity.

[github-actions]

This PR is stale because it has been open for 30 days with no activity.

[arhadthedev]

The test.test_pdb.test_rwatch_command doctest fails:

Failed example:
    with PdbTestInput(['next',
                       'rwatch foo',
                       'continue',
                       'continue',
                       'continue',
                       'continue',
                       'continue',
                       'continue',
                       'continue',
                       'continue']):
        test_function()
Expected:
    > <doctest test.test_pdb.test_rwatch_command[0]>(3)test_function()
    -> foo = 10
    (Pdb) next
    > <doctest test.test_pdb.test_rwatch_command[0]>(4)test_function()
    -> type(foo)
    (Pdb) rwatch foo
    (Pdb) continue
    <BLANKLINE>
    read watchpoint 10:foo
[...]
Got:
    > <doctest test.test_pdb.test_rwatch_command[0]>(3)test_function()
    -> foo = 10
    (Pdb) next
    > <doctest test.test_pdb.test_rwatch_command[0]>(4)test_function()
    -> type(foo)
    (Pdb) rwatch foo
    (Pdb) continue
    <BLANKLINE>
    read watchpoint 4:foo
[...]

read watchpoint 4:foo comes from the freshly added functions:

cpython/Lib/pdb.py

Line 701 in e1daed0

self._do_watch(arg, 'read watchpoint')

cpython/Lib/pdb.py

Lines 673 to 683 in e1daed0

	def _do_watch(self, arg, type):
	if not arg:
	# Print out all breakpoint
	self.do_break(None)
	return None
	try:
	eval(arg, self.curframe.f_locals)
	except NameError:
	self.error('No symbol "%s" in current context' % arg)
	return None
	self.set_watch(arg, self.curframe, type)

cpython/Lib/bdb.py

Lines 543 to 553 in e1daed0

	def set_watch(self, var_name, var_frame, bptype):
	try:
	var_value = copy.copy(eval(var_name, var_frame.f_locals))
	except NameError:
	return 'Variable %s does not exist' % var_name
	list = self.breaks.setdefault(bptype, [])
	if var_name not in list:
	list.append(var_name)
	Breakpoint(None, None, var_name=var_name, var_value=var_value,
	var_frame=var_frame, bptype=bptype)
	return None

I cannot recognize what the problem is though.

[github-actions]

This PR is stale because it has been open for 30 days with no activity.

[read-the-docs-community]

Documentation build overview

📚 cpython-previews | 🛠️ Build #35337485 | 📁 Comparing c47f63a against main (4be1d35)

  🔍 Preview build  

4 files changed

± library/bdb.html
± library/dis.html
± library/pdb.html
± whatsnew/changelog.html

[gaogaotiantian]

The approach itself is very fagile, and it won't work for all the cases. Also it will slow down the execution quite a bit. I agree that it's nice to have watchpoints in pdb. Mark and I had a discussion today about implementing one with the dict watcher. I'll draft something. I don't believe we can get a good enough result from this direction. I'll close the PR for now, but if anyone is super interested in working on this, feel free to reach out.