I am trying to get file upload working in a ui-component admin form. The file input field is coming from a htmlContent block. This is all sitting in a <form xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Ui:etc/ui_configuration.xsd"> element.

Now the issue is that the form element is not actually being rendered as html, as such I cannot add/apply enctype="multipart/form-data" to this form and $_FILES remains empty upon submitting.

Attempts to change the uiComponent to include form element and/or enctype definition failed as it doesn't allow usage of such elements/attributes in the ui-component file directly (collapsible.xhtml). How to move forward with this?

I am trying to get file upload working in a ui-component admin form. The file input field is coming from a htmlContent block. This is all sitting in a <form xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Ui:etc/ui_configuration.xsd"> element.

Now the issue is that the form element is not actually being rendered as html, as such I cannot add/apply enctype="multipart/form-data" to this form and $_FILES remains empty upon submitting.

Attempts to change the uiComponent to include form element and/or enctype definition failed as it doesn't allow usage of such elements/attributes in the ui-component file directly (collapsible.xhtml). How to move forward with this?

Code example:

Form definition

<form xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Ui:etc/ui_configuration.xsd">
 <argument name="data" xsi:type="array">
 [...]
 <item name="template" xsi:type="string">templates/form/collapsible</item>
 <item name="enctype" xsi:type="string">multipart/form-data</item>
 </argument>
 <settings>
 [...]
 </settings>
 <dataSource name="XXX">
 [...]
 </dataSource>
 [...]
 <fieldset name="XXX" sortOrder="20">
 <settings>
 <collapsible>false</collapsible>
 <opened>true</opened>
 <label translate="true">Products</label>
 </settings>
 <htmlContent name="custom_field">
 <block name="html_content_input_field" class="XXXX">
 <arguments>
 <argument name="template" xsi:type="string">
 XXX.phtml
 </argument>
 </arguments>
 </block>
 </htmlContent>
 </fieldset>
</form>

XXX.phtml - Simplified as the file is nested in an array-like structure set up with Knockout

<div>
 <input type="file" name="nameforfile" data-form-part="the-correct-name"/>
</div>

All textual data is send - even the fake file name of the file but not the file itself. I don't need instant upload and/or visible files - Solely the data of the file actually being send to the server.

Raw POST data looks like:

------WebKitFormBoundaryvmSygS0ldVua30Aw
Content-Disposition: form-data; name="author_id"
1
[...] etc