Save identifier module after first getting

[Connormiha]

What kind of change does this PR introduce?
Performance. Cache module identifier after first call.

Did you add tests for your changes?
No

If relevant, link to documentation update:
N/A

Summary

In some plugins we have sort modules function like this:

// From SplitChunksPlugin
const sortByIdentifier = (a, b) => {
	if (a.identifier() > b.identifier()) return 1;
	if (a.identifier() < b.identifier()) return -1;
	return 0;
};

Method identifier() can be run many times while sorting. Each call identifier() calculates identifier from options. We can cache it to avoid repeated calculate.

Does this PR introduce a breaking change?
No

Other information

[webpack-bot]

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

[ooflorent]

Could you compute this within the constructor?

[Connormiha]

Why do you want to save it inside constructor instead of lazy compute?

[ooflorent]

We did it this way on other module classes. Moreover, identifier is computed at least once. There is no benefit to compute it lazily.

[Connormiha]

I changed it in MultiModule.js

[sokra]

Move identifier creation into constructor like with the MultiModule.

Move it into a _createIdentifier() function and call this in the constructor.

[webpack-bot]

@Connormiha Thanks for your update.

I labeled the Pull Request so reviewers will review it again.

@sokra Please review the new changes.

[sokra]

Thanks