Features for refactoring automatically offending code (pylint autofix)

[idiomaticrefactoring]

Current problem

Recently, a paper could automatically refactor non-idiomatic Python code with nine Python idioms: List/set/dict-comprehension, chain-comparison, truth-value-test, loop-else, star-in-function-call, assign-multiple-targets, for-multiple-targets. And they pulled some requests to GitHub projects and many project members like the feature. And some developers proposed issues for Pylint project such as #5800, a developer said “Would it be an idea for Pylint to output the suggested refactor to the user” in Pylint.

Therefore, I would like to try to integrate the functionality into Pylint, what do you think of the idea？

For example, for the list-comprehension, the paper could refactor the code from GitHub project,

input_files = []
for root, dirs, files in os.walk(path):
             for file in files:
                 if file.endswith(".pbxproj"):
                     input_files.append(path + file)

into

input_files = [path + file for (root, dirs, files) in os.walk(path) 
                                        for file in files if file.endswith('.pbxproj')]

.
For another example, for the for-multiple-targets, the paper could refactor the code from GitHub project：

for items in params_grads:
                 assert items[0].name is not model.embed1.weight.name
                 assert items[0].name is not model.linear_1.weight.name

into

for (items_0, *items_len) in params_grads:
                 assert items_0.name is not model.embed1.weight.name
                 assert items_0.name is not model.linear_1.weight.name

Desired solution

If I could do this, currently I want to refer to the source code of Refactoring checker. Maybe I want to create a new class for each python idiom and register them in https://github.com/PyCQA/pylint/blob/main/pylint/checkers/refactoring/__init__.py. And then, I maybe refer to https://github.com/PyCQA/pylint/blob/055c1920140ebf36501d30307d5ab86965ae185f/pylint/checkers/refactoring/refactoring_checker.py to implement the details of code refactoring.

For example,

1. adding msg for each refactoring
2. checking code whether is refactorable
3. giving suggestions with added msg like Refactoring checker, such as printing "RXXXX: we could refactor ... into ...".

How about the method or some suggestions?

Additional context

https://arxiv.org/abs/2207.05613

[Pierre-Sassoulas]

Thank you for creating the issue. This is something we often talk about as there's some message that give the replacement outright in text and auto fixing would make a lot of sense. But we did not have an issue for it yet.

Take for example the for_any_all checker, the expected code is clearly given in the message.

It was proposed that it would be better as a standalone command and project with a different release cycle than pylint, for simplicity. Even if most pylint contributors would probably be interested in participating.

There's some design to consider:

• Do we reuse the code of the checkers from pylint (maybe adding a hook to an autofix when using add_message) ? This would be more suited to something integrated in pylint
• Do we code it from scratch instead with a completely new design ? It would be more work at the beginning but less later on (?). We could refactor checkers without breaking the "pylint-autofix" (btw we need a name).

The organization we would create the repository in is also something we need to discuss. (Right now we do not have admin right in PyCQA and can't create a new repository among other issues).