Inserting a template that uses an extension tag that adds one or more (style) modules to the page does not result in VisualEditor loading those modules.

When inserting a "Code block" (the syntaxhighlight extension tag) using VisualEditor, the ext.pygments module is manually loaded by the ve.ce.MWSyntaxHighlightNode class.

Generic logic for this does exist in VisualEditor, but is only used after saving an edit. Then, ve.init.mw.DesktopArticleTarget will load any missing modules provided by the parser, as well as new values from jsconfigvars.

However these three places in VisualEditor do not use this:

• Inserting or updating a template call.
• Inserting or updating an extension tag (internal base class).
• Inserting a mediawiki user signature.

https://github.com/wikimedia/mediawiki-extensions-VisualEditor/blob/f89a6a388096bcfe1b080a36a93fd0dbe9bc6553/modules/ve-mw/ce/nodes/ve.ce.MWSignatureNode.js#L85-L103
https://github.com/wikimedia/mediawiki-extensions-VisualEditor/blob/f89a6a388096bcfe1b080a36a93fd0dbe9bc6553/modules/ve-mw/ce/nodes/ve.ce.MWExtensionNode.js#L73-L80
https://github.com/wikimedia/mediawiki-extensions-VisualEditor/blob/f89a6a388096bcfe1b080a36a93fd0dbe9bc6553/modules/ve-mw/ce/nodes/ve.ce.MWTransclusionNode.js#L137-L166

I imagine these could also expose the modules array from the parse API and pass it to mw.loader.loader().

Example:

1. https://www.mediawiki.org/wiki/Project:Sandbox?action=edit
2. Insert Template
3. Name "Phpi"
4. Content parameter "$foo = foo();"
5. Insert

The pygments module is not loaded. Text is unstyled. After saving, the text is styled.