INPUT

class MyClass {
  static myProperty = value;
  method() {}
}

ACTUAL OUTPUT

var MyClass = function () {
  function MyClass() {
    _classCallCheck(this, MyClass);
  }

  _createClass(MyClass, [{
    key: "method",
    value: function method() {}
  }]);

  return MyClass;
}();

MyClass.myProperty = value;

EXPECTED OUTPUT

var MyClass = function () {
  function MyClass() {
    _classCallCheck(this, MyClass);
  }

  _createClass(MyClass, [{
    key: "method",
    value: function method() {}
  }]);

+  MyClass.myProperty = value;

  return MyClass;
}();

- MyClass.myProperty = value;

PROBLEM

Tree-shaking flat bundles. By assigning property to an unused variable we prevent possibility to tree-shake the unused variable as its treated as side effect. More can be read here.

This won't immediately allow for tree-shaking classes as they are still usually transpiled to IIFEs which means for uglify a potential side effect risk (hard to statically determine if running the function will cause a side effect) and needs for it to work the function call needs to be decorated with /*#__PURE__*/ comment - the issue for this is already created. The issue described here (statics) is also mentioned in the other thread, but I'm creating this to separate those 2 as they can be treated as unrelated.

In the other thread the simple implementation of this was even proposed by @kzc here. It's a good start, however there is a problem with the approach - we need to support both usages:

• babel-plugin-transform-class-properties + babel-plugin-transform-es2015-classes
• babel-plugin-transform-class-properties alone

Where the proposed approach deals only with the first one.