gh-92546: Fix invalid call in pprint executed as a script

[arhadthedev]

Before the fix:

C:\Users\oleg\Documents\dev\notmine\cpython>python -m pprint
Running Release|x64 interpreter...
Traceback (most recent call last):
  File "<frozen runpy>", line 198, in _run_module_as_main
  File "<frozen runpy>", line 88, in _run_code
  File "C:\Users\oleg\Documents\dev\notmine\cpython\Lib\pprint.py", line 671, in <module>
    _perfcheck()
    ^^^^^^^^^^^^
  File "C:\Users\oleg\Documents\dev\notmine\cpython\Lib\pprint.py", line 646, in _perfcheck
    p._safe_repr(object, {}, None, 0, True)
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: PrettyPrinter._safe_repr() takes 5 positional arguments but 6 were given

After the fix:

C:\Users\oleg\Documents\dev\notmine\cpython>python -m pprint
Running Release|x64 interpreter...
_safe_repr: 1.7387325000017881
pformat: 3.657650000001013

Issue: gh-92546.

[arhadthedev]

Need backporting to 3.11 and 3.10 only. 3.9 runs flawlessly.

[ericvsmith]

It would be good to add a test for this so we don't get out of sync in the future. I don't think we need to call it through __main__, but it would be good to call perfcheck() directly, at least to make sure it doesn't fail.

[rhettinger]

Please also request a review from the dev who introduced the bug. This is an important part of the feed back loop.

[iritkatriel]

Thank for reporting. We typically commit a bugfix together with a unit test that will prevent the bug reoccurring. I'm not sure though whether _perfcheck is a feature that needs to be fixed (is it user facing?) or dead code that needs to be removed or a test that needs to move to the test module.

Any idea what it's for?

[rhettinger]

It isn't user facing and it isn't dead. We sometime have code the is just for us in a main section. For example, the random module also has some performance measurement code and example distributions — we use that sometimes while maintaining the module.

[iritkatriel]

If it’s useful then it needs a test.

(And it would probably be even more useful as a pyperformance benchmark, where it would be tracked on a regular basis.)

[itaisteinherz]

I'd write a sanity test which verifies that $ python -m pprint works. More unit tests could then be added in the future if needed, but a simple sanity test is enough for now.

From what I can tell, that is what didn't work for @ArturKhuziakhmetov when they opened #92546, and it makes sense to test. It is surely user-facing, and should work.

[itaisteinherz]

Update: I just noticed I missed some of @rhettinger's comments. Since this is undocumented functionality, refraining from testing it may make sense. However, seeing broken code shipped in production builds raises a red flag for me.

[merwok]

But the production code is really the functions that people import from the pprint module, not the unofficial script functionality.

[ericvsmith]

@iritkatriel : it doesn't seem very useful to me, and as far as I can tell it's not documented. I suggest either adding tests for it or deleting it, with a preference to delete it.

[arhadthedev]

Closing in favor of python/pyperformance#222 and gh-94613.