Function parseWhenTrigger

packages/compiler/src/render3/r3_deferred_triggers.ts:92–125

(
  {expression, sourceSpan}: html.BlockParameter,
  bindingParser: BindingParser,
  triggers: t.DeferredBlockTriggers,
  errors: ParseError[],
)

/** Parses a `when` deferred trigger. */
export function parseWhenTrigger(
  {expression, sourceSpan}: html.BlockParameter,
  bindingParser: BindingParser,
  triggers: t.DeferredBlockTriggers,
  errors: ParseError[],
): void {
  const whenIndex = expression.indexOf('when');
  const whenSourceSpan = new ParseSourceSpan(
    sourceSpan.start.moveBy(whenIndex),
    sourceSpan.start.moveBy(whenIndex + 'when'.length),
  );
  const prefetchSpan = getPrefetchSpan(expression, sourceSpan);
  const hydrateSpan = getHydrateSpan(expression, sourceSpan);

  // This is here just to be safe, we shouldn't enter this function
  // in the first place if a block doesn't have the "when" keyword.
  if (whenIndex === -1) {
    errors.push(new ParseError(sourceSpan, `Could not find "when" keyword in expression`));
  } else {
    const start = getTriggerParametersStart(expression, whenIndex + 1);
    const parsed = bindingParser.parseBinding(
      expression.slice(start),
      false,
      sourceSpan,
      sourceSpan.start.offset + start,
    );
    trackTrigger(
      'when',
      triggers,
      errors,
      new t.BoundDeferredTrigger(parsed, sourceSpan, prefetchSpan, whenSourceSpan, hydrateSpan),
    );
  }
}

/** Parses an `on` trigger */
export function parseOnTrigger(