Do not initialize members to null in "process a URLPatternInit"

[jeremyroman]

It is not valid for these dictionary members to be null, since they are defined to, if present, hold a USVString value. Instead, these should be omitted from the result dictionary altogether if no string was provided to this algorithm.

This addresses the concern raised in https://github.com/whatwg/urlpattern/issues/202#issuecomment-1893280263.

• [x] At least two implementers are interested (and none opposed):
  • Google Chrome
  • n/a (change is simply fixing a bug in a non-controversial way, per this comment)
• [x] Tests are written and can be reviewed and commented upon at:
  • n/a (this is a fix to how the spec expresses this, but does not represent a behavior change, and existing tests cover this behavior)
• [x] Implementation bugs are filed:
  • Chromium: n/a (believed to work correctly in Chromium)
  • Gecko: https://bugzilla.mozilla.org/show_bug.cgi?id=1731418 (vendor does not yet implement the spec)
  • WebKit: [no known URLPattern bug] (vendor does not yet implement the spec)
  • Deno: n/a (no reason to believe a change is required)
  • kenchris/urlpattern-polyfill: n/a (no reason to believe a change is required)
• [x] MDN issue is filed: n/a (change is on a spec detail not expressly documented)
• [x] The top of this comment includes a clear commit message to use.

(See WHATWG Working Mode: Changes for more details.)

---

:boom: Error: 400 Bad Request :boom:

PR Preview failed to build. (Last tried on Jan 26, 2024, 5:02 PM UTC).

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PR Preview relies on a number of web services to run. There seems to be an issue with the following one: :rotating_light: [CSS Spec Preprocessor](https://api.csswg.org/bikeshed/) - CSS Spec Preprocessor is the web service used to build Bikeshed specs. :link: [Related URL](https://api.csswg.org/bikeshed/?url=https%3A%2F%2Fraw.githubusercontent.com%2Fwhatwg%2Furlpattern%2F226dee4d836b2f5e54e2e8e5ad4b358f37df9b0c%2Fspec.bs&force=1&md-status=LS-PR&md-Text-Macro=PR-NUMBER%20212) _If you don't have enough information above to solve the error by yourself (or to understand to which web service the error is related to, if any), please [file an issue](https://github.com/tobie/pr-preview/issues/new?title=Error%20not%20surfaced%20properly&body=See%20whatwg/urlpattern%23212.)._

[sisidovski]

Thanks! It looks the PR preview failed to build. Could you try the build again?

[jeremyroman]

Not sure how to get pr-preview to reattempt, but a preview is available here: https://api.csswg.org/bikeshed/?url=https%3A%2F%2Fraw.githubusercontent.com%2Fjeremyroman%2Furlpattern%2Fprocess-urlpatterninit-null%2Fspec.bs&force=1&md-status=LS-PR&md-Text-Macro=PR-NUMBER%20212

[jeremyroman]

It is an assertion failure to get an entry from a map that it does not contain. https://infra.spec.whatwg.org/#map-get