Can not override UI Component template

Question

Template file (app/code/namespace/module/view/adminhtml/ui-component/product_form.xml)

<?xml version="1.0" encoding="UTF-8"?>
<!--
/**
 * Copyright 2013-2017 Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */
-->
<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/collapsible2</item>
    </argument>
</form>

Does not render app/code/namespace/module/view/adminhtml/ui-component/templates/collapsible2.xhtml

But if I

• Copy vendor/magento/module-catalog/view/adminhtml/ui_component/product_form.xml
• Modify the template line and make it app/code/namespace/module/view/adminhtml/ui-component/product_form.xml,
• Move or delete vendor/magento/module-catalog/view/adminhtml/ui_component/product_form.xml

It works. If I don't move or delete the core file, I can't override the template.

Answer 1

UI Commponent of Extension developers cannot extend this XSD scheme and introduce new components, but can customize existing ones enter here documentation

Answer 2

You are doing wrong template path

<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/collapsible2</item>
</argument>

The path templates/collapsible2 should be

app/code/namespace/module/view/adminhtml/ui-component/templates/collapsible2.xhtml

in app/code/namespace/module/etc/module.xml should add depend on Magento_Ui