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gh-103693: Add convenience variable feature to pdb #103694

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Merged
merged 7 commits into from
May 3, 2023
Merged

gh-103693: Add convenience variable feature to pdb #103694

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7db9d37
Add convenience variable feature
gaogaotiantian Apr 22, 2023
f7a11af
Change _return to _retval
gaogaotiantian Apr 22, 2023
a202abf
📜🤖 Added by blurb_it.
blurb-it[bot] Apr 22, 2023
1415210
Use exception value instead of tuple
gaogaotiantian Apr 23, 2023
ac23148
Update Doc/library/pdb.rst
gaogaotiantian May 1, 2023
150250b
Update docs and whatsnew
gaogaotiantian May 1, 2023
f626d36
Update Doc/library/pdb.rst
gaogaotiantian May 1, 2023
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Add convenience variable feature
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@gaogaotiantian
gaogaotiantian committed Apr 22, 2023
commit 7db9d37f9e2916af7b9b9954529da83cedc93eac
13 changes: 13 additions & 0 deletions 13 Doc/library/pdb.rst
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Expand Up @@ -263,6 +263,19 @@ the commands; the input is split at the first ``;;`` pair, even if it is in the
middle of a quoted string. A workaround for strings with double semicolons
is to use implicit string concatenation ``';'';'`` or ``";"";"``.

To set temporary global variables, use *convenience variable*. A *convenience
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variable* is a variable whose name starts with ``$``. For example, ``$foo = 1``
set a global variable ``$foo`` which you can use in the debugger session. The
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*convenience variables* are cleared when the program resumes execution so it's
less likely to interfere with your program compared to using normal variables
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like ``foo = 1``.

There are three preset *convenience variables*:

* ``$_frame``: the current frame you are debugging
* ``$_return``: the return value if the frame is returning
* ``$_exception``: the ``(exc_type, exc_value)`` tuple if the frame is raising an exception

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.. index::
pair: .pdbrc; file
triple: debugger; configuration; file
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21 changes: 21 additions & 0 deletions 21 Lib/pdb.py
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Expand Up @@ -270,6 +270,8 @@ def forget(self):
self.lineno = None
self.stack = []
self.curindex = 0
if hasattr(self, 'curframe') and self.curframe:
self.curframe.f_globals.pop('__pdb_convenience_variables', None)
self.curframe = None
self.tb_lineno.clear()

Expand All @@ -288,6 +290,11 @@ def setup(self, f, tb):
# locals whenever the .f_locals accessor is called, so we
# cache it here to ensure that modifications are not overwritten.
self.curframe_locals = self.curframe.f_locals
self.set_convenience_variable('_frame', self.curframe)
if '__return__' in self.curframe_locals:
self.set_convenience_variable('_return', self.curframe_locals['__return__'])
if '__exception__' in self.curframe_locals:
self.set_convenience_variable('_exception', self.curframe_locals['__exception__'])
return self.execRcLines()

# Can be executed earlier than 'setup' if desired
Expand Down Expand Up @@ -394,6 +401,7 @@ def _cmdloop(self):
self.message('--KeyboardInterrupt--')

# Called before loop, handles display expressions
# Set up convenience variable containers
def preloop(self):
displaying = self.displaying.get(self.curframe)
if displaying:
Expand Down Expand Up @@ -477,6 +485,9 @@ def precmd(self, line):
next = line[marker+2:].lstrip()
self.cmdqueue.append(next)
line = line[:marker].rstrip()

# Replace all the convenience variables
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line = re.sub(r'\$([a-zA-Z_][a-zA-Z0-9_]*)', r'__pdb_convenience_variables["\1"]', line)
return line

def onecmd(self, line):
Expand Down Expand Up @@ -527,6 +538,15 @@ def message(self, msg):
def error(self, msg):
print('***', msg, file=self.stdout)

# convenience variables

def set_convenience_variable(self, name, value):
if not hasattr(self, 'curframe') or not self.curframe:
return
if '__pdb_convenience_variables' not in self.curframe.f_globals:
self.curframe.f_globals['__pdb_convenience_variables'] = {}
self.curframe.f_globals['__pdb_convenience_variables'][name] = value

# Generic completion functions. Individual complete_foo methods can be
# assigned below to one of these functions.

Expand Down Expand Up @@ -1018,6 +1038,7 @@ def _select_frame(self, number):
self.curindex = number
self.curframe = self.stack[self.curindex][0]
self.curframe_locals = self.curframe.f_locals
self.set_convenience_variable('_frame', self.curframe)
self.print_stack_entry(self.stack[self.curindex])
self.lineno = None

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78 changes: 78 additions & 0 deletions 78 Lib/test/test_pdb.py
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Expand Up @@ -746,6 +746,84 @@ def test_pdb_where_command():
(Pdb) continue
"""

def test_convenience_variables():
"""Test convenience variables

>>> def util_function():
... import pdb; pdb.Pdb(nosigint=True, readrc=False).set_trace()
... try:
... raise Exception('test')
... except:
... pass
... return 1

>>> def test_function():
... util_function()

>>> with PdbTestInput([ # doctest: +ELLIPSIS, +NORMALIZE_WHITESPACE
... '$_frame.f_lineno', # Check frame convenience variable
... '$a = 10', # Set a convenience variable
... '$a', # Print its value
... 'p $a + 2', # Do some calculation
... 'u', # Switch frame
... '$_frame.f_lineno', # Make sure the frame changed
... '$a', # Make sure the value persists
... 'd', # Go back to the original frame
... 'next',
... '$a', # The value should be gone
... 'next',
... '$_exception[1]', # Check exception convenience variable
... 'next',
... '$_exception', # Exception should be gone
... 'return',
... '$_return', # Check return convenience variable
... 'continue',
... ]):
... test_function()
> <doctest test.test_pdb.test_convenience_variables[0]>(3)util_function()
-> try:
(Pdb) $_frame.f_lineno
3
(Pdb) $a = 10
(Pdb) $a
10
(Pdb) p $a + 2
12
(Pdb) u
> <doctest test.test_pdb.test_convenience_variables[1]>(2)test_function()
-> util_function()
(Pdb) $_frame.f_lineno
2
(Pdb) $a
10
(Pdb) d
> <doctest test.test_pdb.test_convenience_variables[0]>(3)util_function()
-> try:
(Pdb) next
> <doctest test.test_pdb.test_convenience_variables[0]>(4)util_function()
-> raise Exception('test')
(Pdb) $a
*** KeyError: 'a'
(Pdb) next
Exception: test
> <doctest test.test_pdb.test_convenience_variables[0]>(4)util_function()
-> raise Exception('test')
(Pdb) $_exception[1]
Exception('test')
(Pdb) next
> <doctest test.test_pdb.test_convenience_variables[0]>(5)util_function()
-> except:
(Pdb) $_exception
(<class 'Exception'>, Exception('test'))
(Pdb) return
--Return--
> <doctest test.test_pdb.test_convenience_variables[0]>(7)util_function()->1
-> return 1
(Pdb) $_return
1
(Pdb) continue
"""

def test_post_mortem():
"""Test post mortem traceback debugging.

Expand Down
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