Method _scopeSelector

packages/compiler/src/shadow_css.ts:650–688

({
    selector,
    scopeSelector,
    hostSelector,
    isParentSelector = false,
  }: {
    selector: string;
    scopeSelector: string;
    hostSelector: string;
    isParentSelector?: boolean;
  })

  // for example `selector = 'a:where(.one)'` could be the parent, while recursive call
  // would have `selector = '.one'`.
  private _scopeSelector({
    selector,
    scopeSelector,
    hostSelector,
    isParentSelector = false,
  }: {
    selector: string;
    scopeSelector: string;
    hostSelector: string;
    isParentSelector?: boolean;
  }): string {
    // Split the selector into independent parts by `,` (comma) unless
    // comma is within parenthesis, for example `:is(.one, two)`.
    // Negative lookup after comma allows not splitting inside nested parenthesis,
    // up to three levels (((,))).
    const selectorSplitRe =
      / ?,(?!(?:[^)(]*(?:\([^)(]*(?:\([^)(]*(?:\([^)(]*\)[^)(]*)*\)[^)(]*)*\)[^)(]*)*\))) ?/;

    return selector
      .split(selectorSplitRe)
      .map((part) => part.split(_shadowDeepSelectors))
      .map((deepParts) => {
        const [shallowPart, ...otherParts] = deepParts;
        const applyScope = (shallowPart: string) => {
          if (this._selectorNeedsScoping(shallowPart, scopeSelector)) {
            return this._applySelectorScope({
              selector: shallowPart,
              scopeSelector,
              hostSelector,
              isParentSelector,
            });
          } else {
            return shallowPart;
          }
        };
        return [applyScope(shallowPart), ...otherParts].join(' ');
      })
      .join(', ');
  }

  private _selectorNeedsScoping(selector: string, scopeSelector: string): boolean {
    const re = this._makeScopeMatcher(scopeSelector);