Set HMR log level.

[lbogdan]

Second take at fixing the HMR logging issue (first was here) - not being able to turn off HMR's console logging. This change makes HMR respect webpack-dev-server's clientLogLevel.
It uses webpack/hot/log merged here.

What kind of change does this PR introduce?
This is a bugfix.

Did you add or update the examples/?
None needed.

Summary
See #925.

Does this PR introduce a breaking change?
This needs a webpack version with webpack/webpack#4960 merged, otherwise require("webpack/hot/log") will error. That's why the tests failed.

[lbogdan]

Maybe we should check if webpack/hot/log exists?

var hotCtx = require.context("webpack/hot", false, /^\.\/log$/);
if(hotCtx.keys().length > 0) {
  hotCtx("./log").setLogLevel(level);
}

[codecov]

Codecov Report

Merging #926 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #926   +/-   ##
=======================================
  Coverage   72.13%   72.13%           
=======================================
  Files           4        4           
  Lines         463      463           
  Branches      139      139           
=======================================
  Hits          334      334           
  Misses        129      129

---

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[shellscape]

Looks good, but we need to wait for a pending major release before we merge. Didn't want to leave you hanging there.

[lbogdan]

A webpack release, you mean?

[shellscape]

We're actually going to be doing a webpack-dev-server major release soon. It may correspond with webpack.

[lbogdan]

Makes sense. It would be nice to be able to get rid of the webpack/hot/log check, like in the initial commit. Thanks for the heads up!

[shellscape]

This needs a webpack version with webpack/webpack#4960 merged, otherwise require("webpack/hot/log") will error. That's why the tests failed.

@lbogdan since this module is going to continue to support older versions of webpack, we're going to need some error catching around this change. We can't just let it throw cause it'll affect those unable to upgrade webpack.

once we get that in place I think we'll be good to go on this

[lbogdan]

@shellscape The last commit has error catching (more like "feature" checking, actually). That's why the tests pass. Can you please check?

[shellscape]

@lbogdan cool, looks good to me. there's a conflict that needs resolving and then we can merge

[lbogdan]

@shellscape Fixed conflicts, everything looks good.

Also, I saw that with #921 webpack-dev-server is now using the loglevel package for logging. Maybe use it in webpack, too?

[shellscape]

Unfortunately I'm not privy to the workings of webpack main. It might be worth raising an issue there.

[lbogdan]

Oh, ok, I was under the impression that webpack and webpack-dev-server have pretty much the same maintainers. 😃

[shellscape]

I think there's some cross-polination between them all, but it's not 1:1