hi, i have an security exception that say "Unexpected field '__address.street_id' in POST data" i know that happens because the plugin add an extra input with "__" name, when i do the submit the inputs still exist, and the security component send the exception.

I was curious and looked into your plugin yesterday evening.

Why not having two:

• Plain DatalistWidget (just like normal select)
• DatalistJsWidget etc with JS (and maybe even JS fallback for non supportive browsers = shim) for your additional functionality?

I also found a few flaws in your code
The default value (when posting a form and it didnt validate) is lost on display.

Check my fixed version test:

    'datalist' => '<input type="text" id="{{id}}" name="{{name}}" list="datalist-{{id}}" autocomplete="off"{{inputAttrs}}><datalist id="datalist-{{id}}"{{datalistAttrs}}>{{content}}</datalist>',

and

    $default = isset($data['val']) ? $data['val'] : null;
    unset(...);

    $inputData['value'] = $default;
    $inputAttrs = $this->_templates->formatAttributes($inputData);

    $datalistAttrs = $this->_templates->formatAttributes($data);
    return $this->_templates->format(
        'datalist',
        [
            'name' => $name,
            'inputAttrs' => $inputAttrs,
            'datalistAttrs' => $datalistAttrs,
            'content' => implode('', $options),
            'id' => $data['id'],
        ]
    );

Also, no constructor overwrite needed, or interface implement (parent does that).

You should add it to https://github.com/FriendsOfCake/awesome-cakephp#templating

If the model has belongsToMany accosiation for the datalist and only one value is selected it does not save.