Run compiler in nextTick when callback provided

[piecyk]

What kind of change does this PR introduce?

With this change it would be possible to register event on compiler when callback is provided.

For example with current implementation, this will not log for first run as webpack already started

let compiler = webpack(options, callback);

compiler.hooks.watchRun.tap('Foo', (compilation) => {
  logger.success(`Compilation starting...`);
});

Would suggest to wrap with process.nextTick. Having this would be possible to refactor webpack-cli watch logic and fix the DeprecationWarning on callback webpack/webpack-cli#1918

Did you add tests for your changes?
No

Does this PR introduce a breaking change?
No

What needs to be documented once your changes are merged?

There is any

[webpack-bot]

For maintainers only:

• This needs to be documented (issue in webpack/webpack.js.org will be filed when merged)
• This needs to be backported to webpack 4 (issue will be created when merged)

[webpack-bot]

Thank you for your pull request! The most important CI builds succeeded, we’ll review the pull request soon.

[piecyk]

There is workaround, rather than using compiler instance, push a plugin to options that would receive compiler making it possible to run on first run. Looks like there is no need for this change.

[webpack-bot]

It looks like this Pull Request doesn't include enough test cases (based on Code Coverage analysis of the PR diff).

A PR need to be covered by tests if you add a new feature (we want to make sure that your feature is working) or if you fix a bug (we want to make sure that we don't run into a regression in future).

@piecyk Please check if this is appliable to your PR and if you can add more test cases.

Read the test readme for details how to write test cases.

[piecyk]

Let's close this, using plugin should be enough.