Bug 303059 – Default value of custom property not recognizing by CSS Style Container Query with certain formatting

• Component: CSS
• Status: RESOLVED FIXED

[Rogier de Ruijter]

When using a custom property with a default value it is not recognized in a  style container query, when it is formatted with e.g. prettier. This does work in Chrome.

In short:

```
html {
  /* valid */
  --my-container-var: var(--my-undefined-var, "my-default-value");

  /* invalid */
  --my-container-var: var(
     --my-undefined-var,
     "my-default-value"
  );

}

body {
   @container style(--my-container-var: "my-default-value") {
     --my-font: "Helvetica Neue", Helvetica, Arial, sans-serif;
   }
}

p {
  font-family: var(--my-font);
}

```

[Radar WebKit Bug Importer]

<rdar://problem/165627262>

[Ahmad Saleem]

Pull request: https://github.com/WebKit/WebKit/pull/65609

[EWS]

Committed 313957@main (2f8d1192d466): <https://commits.webkit.org/313957@main>

Reviewed commits have been landed. Closing PR #65609 and removing active labels.