Map class property assertion fails when using babel-plugin-transform-runtime

[jedwards1211]

This is a:

• Bug Report
• Feature Request
• Question
• Other

Which concerns:

• flow-runtime
• babel-plugin-flow-runtime
• flow-runtime-validators
• flow-runtime-mobx
• flow-config-parser
• The documentation website

---

What is the current behaviour?

Code

// @flow
// @flow-runtime assert, annotate

class Foo {
  bar: Map<string, any> = new Map()

  getValue(name: string) {
    return this.bar.get(name)
  }
}

new Foo().getValue('hello')

.babelrc

{
  "presets": [["env", {"targets": {"node": "current"}}], "flow"],
  "plugins": [
    "transform-decorators-legacy",
    ["flow-runtime", {"annotate": false, "assert": false}],
    "transform-runtime",
    "transform-class-properties",
  ],
}

Erroneous error

/Users/andy/iron-pi-webapp/node_modules/flow-runtime/dist/flow-runtime.js:9331
        throw error;
        ^

RuntimeTypeError: Default value for property Foo.bar must be an instance of Map

Expected: Map

Actual: Map

Transpiled code and explanation

babel-plugin-transform-runtime converts usage of Map to _map2.default, where _map2 is:

var _map = require('babel-runtime/core-js/map');

var _map2 = _interopRequireDefault(_map);

But babel-plugin-flow-runtime decorates the class property with a runtime reference to 'Map', which resolves to something else (depending on the environment).

'use strict';

var _defineProperty = require('babel-runtime/core-js/object/define-property');

var _defineProperty2 = _interopRequireDefault(_defineProperty);

var _map = require('babel-runtime/core-js/map');

var _map2 = _interopRequireDefault(_map);

var _dec, _dec2, _class, _desc, _value, _class2, _descriptor;

var _flowRuntime = require('flow-runtime');

var _flowRuntime2 = _interopRequireDefault(_flowRuntime);

function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }

function _initDefineProp(target, property, descriptor, context) {
  if (!descriptor) return;
  (0, _defineProperty2.default)(target, property, {
    enumerable: descriptor.enumerable,
    configurable: descriptor.configurable,
    writable: descriptor.writable,
    value: descriptor.initializer ? descriptor.initializer.call(context) : void 0
  });
}

function _applyDecoratedDescriptor(target, property, decorators, descriptor, context) {
  var desc = {};
  Object['ke' + 'ys'](descriptor).forEach(function (key) {
    desc[key] = descriptor[key];
  });
  desc.enumerable = !!desc.enumerable;
  desc.configurable = !!desc.configurable;

  if ('value' in desc || desc.initializer) {
    desc.writable = true;
  }

  desc = decorators.slice().reverse().reduce(function (desc, decorator) {
    return decorator(target, property, desc) || desc;
  }, desc);

  if (context && desc.initializer !== void 0) {
    desc.value = desc.initializer ? desc.initializer.call(context) : void 0;
    desc.initializer = undefined;
  }

  if (desc.initializer === void 0) {
    Object['define' + 'Property'](target, property, desc);
    desc = null;
  }

  return desc;
}

function _initializerWarningHelper(descriptor, context) {
  throw new Error('Decorating class property failed. Please ensure that transform-class-properties is enabled.');
}

// -runtime assert, annotate

let Foo = (_dec = _flowRuntime2.default.annotate(_flowRuntime2.default.class('Foo', _flowRuntime2.default.property('bar', _flowRuntime2.default.ref('Map', _flowRuntime2.default.string(), _flowRuntime2.default.any())), _flowRuntime2.default.method('getValue', _flowRuntime2.default.param('name', _flowRuntime2.default.string())))), _dec2 = _flowRuntime2.default.decorate(_flowRuntime2.default.ref('Map', _flowRuntime2.default.string(), _flowRuntime2.default.any())), _dec(_class = (_class2 = class Foo {
  constructor() {
    _initDefineProp(this, 'bar', _descriptor, this);
  }

  getValue(name) {
    let _nameType = _flowRuntime2.default.string();

    _flowRuntime2.default.param('name', _nameType).assert(name);

    return this.bar.get(name);
  }
}, (_descriptor = _applyDecoratedDescriptor(_class2.prototype, 'bar', [_dec2], {
  enumerable: true,
  initializer: function () {
    return new _map2.default();
  }
})), _class2)) || _class);


new Foo().getValue('hello');

---

What is the expected behaviour?

---

babel-plugin-flow-runtime should use functions to resolve names at runtime (e.g. _flowRuntime2.default.ref(() => Map, ...) instead of _flowRuntime2.default.ref('Map', ...), so that Babel's module transform doesn't break the reference to Map.

Which package versions are you using?

    "babel-core": "^6.26.0",
    "babel-plugin-flow-runtime": "^0.15.0",
    "babel-plugin-transform-class-properties": "^6.24.1",
    "babel-plugin-transform-decorators-legacy": "^1.3.4",
    "babel-plugin-transform-runtime": "^6.23.0",
    "babel-preset-env": "^1.6.1",
    "babel-preset-flow": "^6.23.0",

---

IssueHunt Summary

Backers (Total: $50.00)

• issuehunt ($50.00)

Submitted pull Requests

• #286 Fix class property refs for transformed builtins
• #298 fix: align Map runtime type reference with transform-runtime
• #308 Fix Map assertions with babel transform-runtime

---

Become a backer now!

Or submit a pull request to get the deposits!

Tips

• Checkout the Issuehunt explorer to discover more funded issues.
• Need some help from other developers? Add your repositories on IssueHunt to raise funds.

[issuehunt-oss]

@issuehunt has funded $50.00 to this issue.

---

• Submit pull request via IssueHunt to receive this reward.
• Want to contribute? Chip in to this issue via IssueHunt.
• Checkout the IssueHunt Issue Explorer to see more funded issues.
• Need help from developers? Add your repository on IssueHunt to raise funds.

[selimeneserd]

Submitted a fix in PR #289: #289

[landeqiming666]

I opened #308 with a focused end-to-end fix for the class-property Map case. It keeps generated class-property references as value references so transform-runtime can rewrite them consistently, and adds the complementary runtime predicate coverage for a Map from another realm.

Validation: yarn --cwd packages/babel-plugin-flow-runtime test (240 passing), yarn --cwd packages/flow-runtime test (169 passing), targeted lint, and git diff --check.