Function getExpressionChangedErrorDetails

packages/core/src/render3/errors.ts:128–172

(
  lView: LView,
  bindingIndex: number,
  oldValue: any,
  newValue: any,
)

 * function description.
 */
export function getExpressionChangedErrorDetails(
  lView: LView,
  bindingIndex: number,
  oldValue: any,
  newValue: any,
): {propName?: string; oldValue: any; newValue: any} {
  const tData = lView[TVIEW].data;
  const metadata = tData[bindingIndex];

  if (typeof metadata === 'string') {
    // metadata for property interpolation
    if (metadata.indexOf(INTERPOLATION_DELIMITER) > -1) {
      return constructDetailsForInterpolation(
        lView,
        bindingIndex,
        bindingIndex,
        metadata,
        newValue,
      );
    }
    // metadata for property binding
    return {propName: metadata, oldValue, newValue};
  }

  // metadata is not available for this expression, check if this expression is a part of the
  // property interpolation by going from the current binding index left and look for a string that
  // contains INTERPOLATION_DELIMITER, the layout in tView.data for this case will look like this:
  // [..., 'id�Prefix � and � suffix', null, null, null, ...]
  if (metadata === null) {
    let idx = bindingIndex - 1;
    while (typeof tData[idx] !== 'string' && tData[idx + 1] === null) {
      idx--;
    }
    const meta = tData[idx];
    if (typeof meta === 'string') {
      const matches = meta.match(new RegExp(INTERPOLATION_DELIMITER, 'g'));
      // first interpolation delimiter separates property name from interpolation parts (in case of
      // property interpolations), so we subtract one from total number of found delimiters
      if (matches && matches.length - 1 > bindingIndex - idx) {
        return constructDetailsForInterpolation(lView, idx, bindingIndex, meta, newValue);
      }
    }
  }
  return {propName: undefined, oldValue, newValue};
}