Behavior changed for textarea elements with on:input:value:to

[chasenlehara]

In CanJS 4.2, if a textarea was bound in a component like this:

Component.extend({
  tag: "my-app",
  view: `
    <textarea on:input:value:to="prop" value:bind="prop">From view</textarea>
    <p>prop: {{prop}}</p>
  `,
  ViewModel: {
    prop: {
      default: "From VM"
    }
  }
});

…the textarea would show From VM as its value. Here’s a demo: https://jsbin.com/rotisapaxi/1/edit?html,js,output

In CanJS 4.3+, the prop gets changed to From view; demo here: https://jsbin.com/quseciqawo/1/edit?html,js,output

I haven’t had a lot of time to debug this issue, but from a quick look through the stack trace, I noticed that can-bind sets up the binding for on:input:value:to and then syncs the values; since that’s technically a one-way child-to-parent binding, it sets the parent to the child’s value. In previous versions of can-stache-bindings, I’m not sure if we skipped that initialization process, or if can-stache-bindings handled it some other way.

[chasenlehara]

@justinbmeyer I think this is a bug but I’d appreciate your confirmation.