Better error messages for mdl-textfield

[kennethkalmer]

I added support for binding errorMessage to something coming from outside the component. Lets say you have existing validations or server-side validations and want to provide feedback to the user, the simple pattern approach provided by the HTMLInputElement doesn't work.

This approach simply observes the errorMessage property, sanitises the value slightly, and calls the HTMLInputElement's setCustomValidity, which in turns triggers MDL to do its thing and apply the correct is-invalid class to the wrapping div...

Pending initial feedback I'll get this implemented on {{mdl-textarea}} too.

[mike-north]

This looks great. Let's get it implemented with mdl-textarea as well in this PR, so we can have one release with consistent support for error messages

[mike-north]

please indicate that this is private (_setValidity)

[kennethkalmer]

@mike-north thanks for the feedback, will roll with this and get it done by the weekend!

[alanpeabody]

This is great, looking forward to using it.

To hijack this PR a bit: Would formatting ember-data error messages directly be something you are interested in supporting?

For example, given post.errors is an DS.Errors object (http://emberjs.com/api/data/classes/DS.Errors.html):

{{mdl-textarea
  label='Title'
  value=post.title
  errors=post.errors.title
}}

Or maybe I should just use a sub-expression?

[kennethkalmer]

@mike-north implemented the textarea part too, apologies for the delays.

@alanpeabody, imho I don't think it is a good idea. Just pass in a computed property with the error, we can't favour one style of validations over another.

[alanpeabody]

@mike-north @kennethkalmer Any update if this will be merged or not?

[20v100]

Looking forward for the merge.

[coveralls]

Coverage increased (+11.2%) to 100.0% when pulling fc74171 on kennethkalmer:better-error-messages into 61ac1ea on mike-north:master.