Respect swup link selector for preloaded links

[daun]

Description

• Found a branch I've been using as private fork in production for a while
• Respect and check swup's link selector option
• The original goal was to support preloading links in SVGs
• But it's useful in general to only load links that match the link selector

Drive-by changes

• Return early from swup.preload(url) if no url is passed in (homepage still works as it should be '/' anyway)

Checks

• The PR is submitted to the master branch
• The code was linted before pushing (npm run lint)
• All tests are passing (npm run test)
• New or updated tests are included
• The documentation was updated as required

[github-actions]

Playwright test results

 88 passed
 4 skipped

Details

 92 tests across 8 suites
 1 minute, 33 seconds
 54e0f8c

Skipped tests

chromium → preload-plugin.spec.ts → active links → preloads links on touchstart
firefox → preload-plugin.spec.ts → active links → preloads links on touchstart
webkit → preload-plugin.spec.ts → active links → preloads links on touchstart
ios → preload-plugin.spec.ts → active links → preloads links on hover

[hirasso]

Will test this should I ever need it 😄

Do you think this should be mentioned in the docs?

[daun]

@hirasso I had to merge from master to fix merge conflicts, please re-approve :)

[daun]

@hirasso I'll double-check that this still respects the link selector — this was meant as a fix for setups where swup is configured to load links in SVGs but the preload plugin didn't support that. In that sense, probably no reason to append the docs as we're aiming for the plugin to just work as configured from the core.

[daun]

@hirasso Please re-review :) I've added some more tests about respecting swup's link selector and upgraded Playwright — apparently Chrome only started observing single SVG links in IntersectionObserver since the most recent version 121 🤠

[hirasso]

Very interesting! That's how we get to be hyper nerds regarding cross-browser knowledge 🤓