fix: do not skip changes when compilation is suspended

[vladar]

This PR aims to solve an issue with skipped changes in Watching.js (when compilation is suspended). See #12898 for details.

What kind of change does this PR introduce?

A bugfix.

Did you add tests for your changes?

Yes.

Does this PR introduce a breaking change?

No.

What needs to be documented once your changes are merged?

This PR doesn't require documentation.

Fixes #12898

[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.

[sokra]

I guess we should not pause the watcher when suspended, so it keeps aggregating changes. Otherwise modifiedFiles etc. do not contain the changes from the first watch event.

[vladar]

I am maybe missing something but it seems to be a dead code anyways, because this.watcher is always null at this point so this if branch with this.watcher.pause() is actually never executed (see line 252)?

webpack/lib/Watching.js

Lines 252 to 266 in f4ae05e

	this.watcher = null;
	if (err) {
	this.compiler.modifiedFiles = undefined;
	this.compiler.removedFiles = undefined;
	this.compiler.fileTimestamps = undefined;
	this.compiler.contextTimestamps = undefined;
	return this.handler(err);
	}
	this.compiler.fileTimestamps = fileTimeInfoEntries;
	this.compiler.contextTimestamps = contextTimeInfoEntries;
	this.compiler.removedFiles = removedFiles;
	this.compiler.modifiedFiles = changedFiles;
	if (this.watcher) {
	this.pausedWatcher = this.watcher;
	this.watcher.pause();

[tu4mo]

Any chance getting this reviewed soon?

[tu4mo]

I updated to latest Gatsby and patched webpack manually with this and #12881, and in my initial tests these seem to have fixed hot reloading issues we are having in gatsbyjs/gatsby#27609.

FYI @sokra

[sokra]

Merged by #13399