Function parsePlaceholder

packages/localize/src/utils/src/messages.ts:286–297

(
  cooked: string,
  raw: string,
)

 *     preceding placeholder, along with the static text that follows.
 */
export function parsePlaceholder(
  cooked: string,
  raw: string,
): {messagePart: string; placeholderName?: string; associatedMessageId?: string} {
  const {text: messagePart, block} = splitBlock(cooked, raw);
  if (block === undefined) {
    return {messagePart};
  } else {
    const [placeholderName, associatedMessageId] = block.split(ID_SEPARATOR);
    return {messagePart, placeholderName, associatedMessageId};
  }
}

/**
 * Split a message part (`cooked` + `raw`) into an optional delimited "block" off the front and the