Add mlint bear

[palash25]

For MATLAB code

https://in.mathworks.com/help/matlab/ref/mlint.html?requestedDomain=true

[gitmate-bot]

GitMate.io thinks possibly related issues are #201 (Add TSLint Bear), #2152 (Add ktlint Bear), #2346 (Add slim-lint bear), #2339 (Add isort bear), and #2297 (Add vale lint bear).

[li-boxuan]

Hi, I get a bit confused. Mlint is just a function that can be run in MATLAB. How can we write a bear for it since a lint bear needs an executable?

[palash25]

maybe we can somehow use the MATLAB compiler for static code analysis using the mlint function. Something like what's been proposed in #2011

[palash25]

But in that case it wouldn't be a difficulty/low issue imo
@li-boxuan

[li-boxuan]

I would like to solve it.

Some concerns:

1. I would suggest using checkcode instead of mlint as Matlab says, mlint is not recommended. Use checkcode instead.

2. I just drafted a lint bear, by using -nodisplay -nodesktop -r "checkcode('<filename>');" arguments. This works as it calls Matlab application to run the checkcode function. However, it takes some time for Matlab to start; if we restart Matlab every time we examine a file, it would be annoying for users as it may take too much time. Any suggestions?

[Makman2]

I would suggest using checkcode instead of mlint as Matlab says, mlint is not recommended. Use checkcode instead.

👍

However, it takes some time for Matlab to start; if we restart Matlab every time we examine a file, it would be annoying for users as it may take too much time. Any suggestions?

Yeah that's a problem. Usually you would start some background service / daemon you would reuse, but that raises the difficulty a bit. Maybe Matlab provides already something for similar purposes?

[li-boxuan]

I don't think Matlab provide something for similar purposes (at least I cannot find one). The normal practice in Matlab is to run checkcode multiple times for each file in one program. Something like

Matlab -nodisplay -nodesktop -r "checkcode('<filename_1>'); checkcode('<filename_2>'); checkcode('<filename_3>');"

I guess coala cannot handle this case.

[li-boxuan]

My bad, mlint is an executable (it is also a function call in Matlab). checkcode is just a wrapper for mlint. (See Gimly/vscode-matlab#26)

@Makman2 I think I can handle this issue now.

[li-boxuan]

I am trying to write tests for MlintBear but I come up with a problem: MATLAB is commercial. How can it pass CI test? Only people with Matlab installed would be able to run the test.

[jayvdb]

Put your bear in new directory /bears/non-free/ , with tests in /tests/non-free/ , and delete both directories in the .CI scripts.

[jayvdb]

In quite a few cases we have rejected non-free linters, because free tools existed, even if not as good, but IMO matlab is a special case. We may end up rejecting this bear, as other maintainers will need to consider this policy question, but at least your CI should be green , and the code not intrusive to the free linters.

A middle ground might be to create a non-free-bears repos ;-)

[saksham189]

If the tests are never run on the CI, how can we know whether the bear is working as intended? What is the need to have a test file in this case? Is it just for the contributor to check and verify?

[jayvdb]

As these are significantly different, we're going to put them in their own repo.
This one is https://gitlab.com/coala/non-free-linter-bears/issues/1