Implement linting on change

[kav2k]

As per this comment in #28, a new feature request:

Actually implement python.linting.lintOnTextChange, to apply linting to the unsaved buffer.

This is a desirable, if nontrivial, function.

See also #313 - if this is implemented, that should be reversed.

[kav2k]

Please update #313 to point to this issue instead, so that people can vote for it.

[brettcannon]

@kav2k you can leave a comment referencing this issue if you want; there shouldn't be anything requiring special privileges to do so.

[kav2k]

Plus, it would make sense to edit the issue text, as it explicitly says "please add your vote 👍 against the following issue #28."

[brettcannon]

@kav2k I removed the mention in the other issue.

[malmaud]

I'll just point out that PyCharm, atom, and sublime already have this. Most language packages for VSCode also have it. So this is really an outlier in terms of missing functionality.
Thanks!

[xguse]

PS: since I cant comment on #313...

It advises:

"python.linting.lintOnSave": true,
"files.autoSave": true

As far as I can tell "files.autoSave": true is not actually an expected state for this option. I may be wrong but when I look at this, the options provide are:

 // Controls auto save of dirty files. Accepted values: 
'off', 
'afterDelay', 
'onFocusChange' (editor loses focus), 
'onWindowChange' (window loses focus). If set to 'afterDelay', you can configure the delay in 'files.autoSaveDelay'.

This is kind of crazy to me. I have to have my file write to disk every second in order to get linting while I write?

I will echo @malmaud on pointing out that this doesn't seem to be a "luxury" setting for most other languages/editors. It was quite surprising to me when I encountered this in this extension.

However, please don't misunderstand my tone: I am VERY thankful for your work so far and would like to point out that having python so well supported for the most part in VS Code was what allowed me to finally leave Atom. It have for the MOST part been a spectacular change.

So thanks.