Template field filling is silently inert for MS Office / OOXML templates

[moodyjmz]

TL;DR

TemplateFieldService::extractFields() only proceeds for mimetypes in Capabilities::MIMETYPES — which holds ODF/legacy formats, not the OOXML ones. Since richdocuments defaults to doc_format=ooxml, the field-extraction/fill-in-dialog feature never fires for the default document/spreadsheet/presentation templates. No error, no log — it just silently returns no fields every time.

Details

Where: lib/Service/TemplateFieldService.php, extractFields():

if (!in_array($file->getMimetype(), Capabilities::MIMETYPES)) {
    return [];
}

The gap: Capabilities::MIMETYPES (lib/Capabilities.php:17-38) contains only ODF and a handful of legacy/alternate formats (.odt, .ods, .odp, .odg, RTF, etc.). All OOXML/MS mimetypes (.docx, .xlsx, .pptx, .doc, .xls, .ppt, and their macro-enabled variants) live in the separate Capabilities::MIMETYPES_MSOFFICE constant (lib/Capabilities.php:40-62), which extractFields() never checks.

Why it matters: RegisterTemplateFileCreatorListener.php defaults to doc_format=ooxml (getAppValue(Application::APPNAME, 'doc_format', 'ooxml')), meaning the document/spreadsheet/presentation template types register with .docx/.xlsx/.pptx mimetypes out of the box. For any install on that default:

1. User picks a custom template with fields defined.
2. Frontend calls listTemplateFields → TemplateManager::getTemplateFields() → TemplateFieldService::extractFields().
3. extractFields() hits the mimetype guard, returns [], unconditionally, regardless of whether the template actually has fields.
4. Frontend's fields.length > 0 check (apps/files/src/views/TemplatePicker.vue in nextcloud/server) is always false, so the "Fill template fields" dialog never appears.

The end result: the template form-filling feature (fields extraction + fill-in dialog) is effectively dead for any install using the default OOXML document format — the only way it currently works is if an admin has switched doc_format to odf.

Suggested fix: have extractFields() check array_merge(Capabilities::MIMETYPES, Capabilities::MIMETYPES_MSOFFICE), matching the guard already used in FileCreatedFromTemplateListener::handle().

Found while reviewing #5971, which is unrelated and does not need to block on this — this is a pre-existing, separate bug.