Iron form not submitting on enter with paper input - polymer

Question

I'm testing out using iron-form with custom elements. The issue I'm having is the form is not being submitted when I press enter. For example this form right here works on enter:
<iron-form>
<form id="loginForm">
<paper-card heading="Welcome Back!" elevation="1" animated-shadow="true">
<div class="card-content">
<input type="text" label="Username" value="{{username}}">
<input type="text" label="Password" value="{{password}}">
</div>
<div class="card-actions">
<button disabled$="[[fetching]]" type="submit">Login</button>
</div>
</paper-card>
</form>
</iron-form>
I have an event listener in my connectedCallback method listening for the iron-form-presubmit event
connectedCallback() {
super.connectedCallback();
this.addEventListener('iron-form-presubmit', function(event) {
event.preventDefault();
alert('working')
});
}
The issue is when I switch the html input elements to paper-input elements the form no longer submits on enter.
<iron-form>
<form id="loginForm">
<paper-card heading="Welcome Back!" elevation="1" animated-shadow="true">
<div class="card-content">
<paper-input type="text" label="Username" value="{{username}}"></paper-input>
<paper-input type="text" label="Password" value="{{password}}"></paper-input>
</div>
<div class="card-actions">
<button disabled$="[[fetching]]" type="submit">Login</button>
</div>
</paper-card>
</form>
</iron-form>

Answer 1

You can use <iron-a11y-keys> to call a submit method when the [enter] key is pressed.
<iron-a11y-keys target="loginForm" keys="enter" on-keys-pressed="submit"></iron-a11y-keys>
<iron-form id="loginForm">
...
</iron-form>
In your custom element definition, add a method:
submit: function () {
this.$.loginForm.submit();
}