Does not work for Extended <file-input>

[marutypes]

I was building an extension of which parses and displays a file preview for each valid file. This does not work in the current implementation of <ajax-form> since the maybeParseFileInput function checks the tag name explicitly. This also means that <ajax-form> does not work with any alternate web component implementations of a file input.

I'm working on a pull request to fix this.

[rnicholus]

As long as your element exposes an input element with a type attribute of "file", there should be no issue. Otherwise, I'm not sure how you would identify such an element.

[marutypes]

• If the input inherits from <file-input>, the input element is hidden inside the shadow dom and doesn't seem to get parsed.
• Since the maybeParseFileInput function checks for the tag name it doesn't get parsed their either.
• Since the maybeParseGenericCustomElement function only checks the value it also doesn't get parsed there...

Have tested this myself using an element which works in a native form.

[rnicholus]

Ajax-form checks for a file-input element, or any input element that has an attribute of type=file. Short of this, I'm not sure how you would identify such an element, short of some very specific convention.

What is your specific plan to address this?

[marutypes]

Well, it is a 'very specific convention' itself to check specifically for file-input. I'd argue it's more general and makes more sense with Polymer's inheritance mechanisms to check if there is a .files attribute similar to how you check for a value attribute in the genericCustomElement parsing.

I say this because it defies user expectations to be disallowed from wrapping or extending due to an overly specific parsing implementation.

[rnicholus]

Yes, that particular convention is in place as I am also the developer of file-input. I suppose that convention could be removed and the custom element parser could be augmented to check for the files property.

[marutypes]

Ok cool. That's what I was doing for the pull request. Glad you get my point :)

[rnicholus]

Yep, as long as an additional specific convention is not introduced, that should be fine. I'd suggest removing the file-input specific code while you're at it.

[rnicholus]

Also, curious what your element's code looks like. I've done quite a bit of work with the File API, scaling, previewing images, etc.

[marutypes]

I'll be putting what I have so far up on webcomponents.io soon. Hadn't seen your link before, looks cool.

[rnicholus]

Released as part of 1.5.4.