fix(pluginutils): only normalize/parse patterns once in createFilter

[lazka]

Rollup Plugin Name: pluginutils

This PR contains:

• bugfix
• feature
• refactor
• documentation
• other

Are tests included?

• yes (bugfixes and features will not be merged without tests)
• no

Breaking Changes?

• yes (breaking changes will not be merged unless absolutely necessary)
• no

If yes, then include "BREAKING CHANGES:" in the first commit message body, followed by a description of what is breaking.

List any relevant issue numbers:

Description

When passing patterns to createFilter() it would normalize and parse the patterns on every call to the returned filter function.

Just do it once at the start instead.

Something I've noticed while working on #1916.

[shellscape]

Thanks for the PR. Could you please add a test that performs multiple calls to getMatcher in succession, and add the PR number in the test description? That will help protect against future possible regressions.

[lazka]

Thanks for the review. Sadly I don't quite understand what type of test you have in mind. Do you want me to move getMatcher to the module level and export it, and then test it? Though it still behaves the same, so there is no way to test the behaviour change.

Adding a spy on picomatch would makes sense, but I couldn't find a way to do that.