a property designated as a mergedProperties will mutate the prototype if set during create

[krisselden]

ember.js/packages/ember-runtime/lib/system/core_object.js

Line 146 in fb49fa0

value = merge(originalValue, value);

this should be value = merge({}, originalValue, value);

[Panman82]

I'm running into this, trying to used an options:{} property as an attribute, with it defined as a mergedProperties:['options']. That way the Component could be extended to define "default" options but then allow usage in templates to override some options with the (hash) helper. Ex: {{foo-bar options=(hash baz="overridden" zoo="new")}} Any progress on this or a workaround?

As a side note, this could probably use the new Ember.assign() polyfil for Object.assign(). I'm sure you're fully aware, but just for reference: http://emberjs.com/blog/2016/02/29/ember-2-4-released.html#toc_code-ember-assign-code

Edit: Looks like master is already using embers assign. If you think passing in an empty hash/object first is all it'll take, I could whip up a PR with that and a test.