Function getErrMessage

lib/internal/assert/utils.js:79–96

* Options consumed by innerFail to construct and throw the AssertionError. * @typedef {object} InnerFailOptions * @property {any} actual Actual value * @property {any} expected Expected value * @property {MessageTuple} message Message * @property {string} operator Operator * @property {Functio

(fn)

 */

function getErrMessage(fn) {
  const tmpLimit = Error.stackTraceLimit;
  const errorStackTraceLimitIsWritable = isErrorStackTraceLimitWritable();
  // Make sure the limit is set to 1. Otherwise it could fail (<= 0) or it
  // does to much work.
  if (errorStackTraceLimitIsWritable) Error.stackTraceLimit = 1;
  // We only need the stack trace. To minimize the overhead use an object
  // instead of an error.
  const err = {};
  ErrorCaptureStackTrace(err, fn);
  if (errorStackTraceLimitIsWritable) Error.stackTraceLimit = tmpLimit;

  let source = getErrorSourceExpression(err);
  if (source) {
    source = StringPrototypeReplace(source, escapeSequencesRegExp, escapeFn);
    return `The expression evaluated to a falsy value:\n\n  ${source}\n`;
  }
}

/**
 * @param {InnerFailOptions} obj