Function deprecate

lib/internal/util.js:177–218

(fn, msg, code, useEmitSync, modifyPrototype = true)

// Returns a modified function which warns once by default.
// If --no-deprecation is set, then it is a no-op.
function deprecate(fn, msg, code, useEmitSync, modifyPrototype = true) {
  // Lazy-load to avoid a circular dependency.
  if (validateString === undefined)
    ({ validateString } = require('internal/validators'));

  if (code !== undefined)
    validateString(code, 'code');

  const emitDeprecationWarning = getDeprecationWarningEmitter(
    code, msg, deprecated, useEmitSync,
  );

  function deprecated(...args) {
    if (!process.noDeprecation) {
      emitDeprecationWarning();
    }
    if (new.target) {
      return ReflectConstruct(fn, args, new.target);
    }
    return ReflectApply(fn, this, args);
  }

  if (modifyPrototype) {
    // The wrapper will keep the same prototype as fn to maintain prototype chain
    // Modifying the prototype does alter the object chains, and as observed in
    // most cases, it slows the code.
    ObjectSetPrototypeOf(deprecated, fn);
    if (fn.prototype) {
      // Setting this (rather than using Object.setPrototype, as above) ensures
      // that calling the unwrapped constructor gives an instanceof the wrapped
      // constructor.
      deprecated.prototype = fn.prototype;
    }

    ObjectDefineProperty(deprecated, 'length', {
      __proto__: null,
      ...ObjectGetOwnPropertyDescriptor(fn, 'length'),
    });
  }

  return deprecated;
}

function deprecateInstantiation(target, code, ...args) {
  assert(typeof code === 'string');