Incompatible with mypy>=0.730

[ziyadedher]

Describe the bug
Prospector is incompatible with mypy versions 0.730 and above. mypy==0.730 introduces an "error summary" statistic in the output that is enabled by default (see this commit). This breaks the mypy module message parsing here due to trying to unpack too many values.

To Reproduce
Steps to reproduce the behavior:

1. pip install 'prospector[with_everything]'
2. pip install mypy==0.730 (should already be installed)
3. prospector

Expected behavior
Prospector should either be compatible with receiving this line from mypy or should pass in the argument --no-error-summary by default. A naive --no-error-summary approach might break compatibility with mypy<0.730, but it would go here.

Environment (please complete the following information):

• OS: Arch Linux
• Tool mypy
• Prospector version 1.1.7
• Python version 3.7.4

Additional Information
Currently, the best workaround I found is to just downgrade mypy to 0.720.

[ziyadedher]

Drafted a simple pull request to address this situation. Feel free to modify it. #346

[rik]

I've submitted #349 for an alternate approach that I think is safer.

[ziyadedher]

I've submitted #349 for an alternate approach that I think is safer.

I think this is a better approach than mine, but it might introduce incompatibilities if Mypy ever changes their summary line message.

[rik]

If it happens, we can always change that logic.

[chocoelho]

As I'm leaning towards the latter PR, I suggest we pin mypy as it updates constantly and keeping tracking of these changes can be recurrent and will tend to promptly break CIs across projects. We can pin using <=0.730 for now. How do you feel @rik and @ziyadedher ?

[chocoelho]

Whenever we can set on this I can work on releasing 1.1.9 instead of 1.2.0 for now.

[rik]

I'm not very fond of meta-tooling putting restrictions on what version underlying tools can use.

	Pros	Cons
Pinning	Guarantee prospector will always work	Downstream can't use newer version until new Prospector release
Not-pinning	New compatible versions are immediately available	Prospector can break with new release. Downstream can pin when it happens

I feel a tool like prospector should strive to keep up with latest versions otherwise it will get in the way of projects using it. As an example, I think I've ran into pylint bugs that are resolved in pylint 2.4+ but prospector pins 2.3.1.

Whenever a tool is incompatible with prospector, maybe temporarily updating the README file with workarounds is an acceptable trade-off?

I say all of that as a user, not a maintainer, so maybe the burden of not pinning is too much.

[chocoelho]

@rik as you may have noticed, the burden can increase a lot by not pinning. As it's usually a few people making the updates, this can be more than we can take as of this moment. I'm working on upgrading to the latest pylint version, alongside the other tools, instead of adding tools/functionalities in the next couple days so we can see how unpinning goes from there.

[rik]

My pylint example was poorly worded. I wanted to illustrate that by pinning versions, users of prospector don't see the issues with newer versions. By not pinning, users run into the issues and may contribute patches to help keep up. I know that was a big factor for my few contributions here.

Regardless of the pinning discussion, would it be possible to merge one of the two PRs for this issue and release a new version of prospector?

[chocoelho]

@rik I totally get you. This may be the way, but I think we may loose a bit the restriction one dep at a time. We can start off with mypy. Can you try updating prospector to 1.2.0.dev1 1.2.0.dev2?

[rik]

I'm really sorry, I made the silly mistake of doing a little "code cleanup" in my PR and it turned out to not work (It doesn't matter how many times I learn this lesson, I keep falling in this trap). So 1.2.0.dev2 breaks all mypy versions.

I've submitted #355 to revert the change and use the flag approach.

[chocoelho]

No worries, that's why I've started doing dev releases instead of just releasing things. I've done the same thing before 😃