Upgrade to del and slash "ESM only" packages

[colinrotherham]

Do we want to upgrade our pinned packages with "ESM only" updates?

There's a two-step process (unfortunately) which needs:

1. Migrate Gulp and Node.js build tasks to ESM #2982
2. Temporarily allow Babel to transpile "ESM only" dependencies for Jest

We need 2) until Node.js unflags --experimental-vm-modules for Jest ECMAScript Modules support

Update: Various related links

• Meta: Native support for ES Modules jestjs/jest#9430
• Roadmap for stabilization of vm modules nodejs/node#37648
• Bump del from 6.1.1 to 7.0.0 #2968
• Bump slash from 3.0.0 to 5.0.0 #3003

[colinrotherham]

Going to make this ready for review as we've discussed it this morning

Likely due to a recent Jest or Babel package update (or the Node.js 18 upgrade) we no longer need to include child packages in transformIgnorePatterns which helps simplify the config changes

[romaricpascal]

Likely due to a recent Jest or Babel package update (or the Node.js 18 upgrade) we no longer need to include child packages in transformIgnorePatterns which helps simplify the config changes

Yeah, that makes things so much leaner than in the previous iteration you showed 🙌🏻 .

question Is there any reason we wouldn't want to configure Babel for all 4 projects? Worried that we one day add one of these packages to the projects and we miss that Babel is not set up for them.

suggestion: Is it worth having a ESM_ONLY_PACKAGES = ['del','slash'] constant we'd build the pattern from as a central point for listing packages we want Babel to process?

[colinrotherham]

Thanks @romaricpascal

question Is there any reason we wouldn't want to configure Babel for all 4 projects? Worried that we one day add one of these packages to the projects and we miss that Babel is not set up for them.

Don't mind at all. Assumed we'd only add it (temporarily) where needed—but pushed again 👍

suggestion: Is it worth having a ESM_ONLY_PACKAGES = ['del','slash'] constant we'd build the pattern from as a central point for listing packages we want Babel to process?

As the code reviewer, would you like that? 😊

Might not be necessary now it's only defined once at the top?