Workflowengine "The given regular expression is invalid"

[R0Wi]

Steps to reproduce

1. Create a new flow (concrete workflow app doesn't matter)
2. Choose File MIME type
3. Choose matches (or does not match)
4. Choose PDF documents (or Folder)

Note: the filters for Images and Office Documents are working.

Expected behaviour

Workflow can be created

Actual behaviour

If i try to save the workflow an error message is raised "The given regular expression is invalid"

Server configuration

Operating system: Ubuntu 20.04

Web server: Apache2

Database: MySql 8.0

PHP version: 7.4

Nextcloud version: 20.0.1

Additional information

• I think this only applies to Nextcloud 20 or later (because like i saw the filter "matches" is not available in NC 19)
• The error message comes from

  server/apps/workflowengine/lib/Check/AbstractStringCheck.php

  Line 91 in 2a154f5

  throw new \UnexpectedValueException($this->l->t('The given regular expression is invalid'), 2);

• The defined regex patterns at

  server/apps/workflowengine/src/components/Checks/FileMimeType.vue

  Line 72 in 2a154f5

  pattern: 'httpd/unix-directory',

  and

  server/apps/workflowengine/src/components/Checks/FileMimeType.vue

  Line 87 in 2a154f5

  pattern: 'application/pdf',

  does not seem to be corret. These are passed to the serverside function mentioned above.

Currently there is also an open issue at R0Wi-DEV/workflow_ocr#32 where multiple users reported this problem.

[kesselb]

Thanks for reporting 👍 I see the same issue on Nextcloud 19.

cc @juliushaertl @blizzz as 'httpd/unix-directory' is not a pattern they cannot use matches as operator. We should probably hide operators which are not compatible to each other. We have the same issue the other way around for File MIME type is Office Documents.

[R0Wi]

Hi since the number of reported issues at the workflow_ocr app regarding this problem is increasing i'd kindly like to ask what are the plans for this? If we like to implement #23666 (comment) i can try to do this if you're willing to accept my PR ? 😃

cc @juliushaertl @blizzz @kesselb

[kesselb]

can try to do this if you're willing to accept my PR

Cool 👍

since the number of reported issues at the workflow_ocr app

A pinned FAQ issue might help with that. At least here at nextcloud/server it helps a bit.

[R0Wi]

A pinned FAQ issue might help with that. At least here at nextcloud/server it helps a bit.

Thanks for the hint, will give it a try 😄

So basically i'd implement it the following way (given that the first column is set to File MIME type):

• The entries of third column (containing the the filetype) are filtered with respect to the second columns choice (comparator)
• If the user sets the comparator to is or is not the filetypes Folder, PDF Documents and Custom mimetype will be shown in the third column
• If the user sets the comparator to matches or does not match the regex based types Images and Office documents will be shown in the third column

Would that be the way to go @kesselb ?

[blizzz]

@R0Wi generally that sounds good to me.

On a second thought, it is quite technical for the end user. An admin might now about regex's and stuff, but for the average user "is (not)" or "matches (not)" or the meaning of it is black magic. The best way would be to eliminate the differences (only keep is _(not)) and figure out what is desired by testing the third columns value.

That would be a bigger change however, and not backportable. This is an advantage of your suggestion, so let's go with it.

Changing the UI more radically (it has effects on the backend bits, too) could be something for 22.

[szaimen]

I suppose this is still valid on NC21.0.2?

[R0Wi]

AFAIK unfortunately yes. Did not manage to create a PR, yet 😢