Fix preview rendering for sharees

[JammingBen]

Description

Previous to this fix, the previews of updated shared files did not change for sharees. Those previews now get re-generated if the content of the files changed.

Related Issue

• Fixes Icon/Preview of image file not updated in non-owner WebUI shared folders after updating the file #39202
• Fixes Previews-thumbnails get out-of-sync when edited by sharer and sharee #31855
• Fixes [ERROR] Gallery does not display the right image but some old version instead gallery#826

How Has This Been Tested?

See steps in #39202

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Database schema changes (next release will require increase of minor version instead of patch)
• Breaking change (fix or feature that would cause existing functionality to change)
• Technical debt
• Tests only (no source changes)

Checklist:

• Code changes
• Unit tests added
• Acceptance tests added
• Documentation ticket raised:
• Changelog item, see TEMPLATE

[phil-davis]

• admin shares text.txt with Alice
• Alice edits text.txt (for example, online with files_texteditor)
• the preview for Alice is not updated
• Alice does ctrl-F5 to refresh, or logs out and back in again - still the preview is not updated
• admin logs in - the updated preview is shown
• Alice logs in - now the updated preview is shown

In the combinations that I tried, it seems that the sharer needs to login and have the file displayed, and then the preview gets updated for everyone.

[AlexAndBear]

@phil-davis, we was always logged with the sharer, so yes could be an issue :/

[JammingBen]

This happens because the preview of the file owner gets deleted when a sharee edits a file. Therefore we don't have a checksum to compare. @phil-davis Please have a look again, should work now.

[phil-davis]

This happens because the preview of the file owner gets deleted when a sharee edits a file. Therefore we don't have a checksum to compare. @phil-davis Please have a look again, should work now.

Works now. I tried combinations of:

• share a single file with a group that has Alice and Brian in it. Alice edits the file, both Brian and admin see the updated preview.
• share a single file with each of Alice and Brian individually. Alice edits the file, both Brian and admin see the updated preview.
• share a folder with a group that has Alice and Brian in it. Alice edits a file in the folder, both Brian and admin see the updated preview.
• share a folder with each of Alice and Brian individually. Alice edits a file in the folder, both Brian and admin see the updated preview.

LGTM

[phil-davis]

LGTM - it should be easy to add a few unit tests to cover the new block of code???

[ownclouders]

💥 Acceptance tests pipeline webUIComments-chrome-mariadb10.2-php7.4 failed. The build has been cancelled.

https://drone.owncloud.com/owncloud/core/32252/124/1

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
1 Code Smell

90.9% Coverage
0.0% Duplication

[phil-davis]

Note: I created issue #39211 to add some acceptance tests. It should not be too hard to keep a record of some simple previews in the acceptance test fixtures, and compare them to the actual generated previews as files are changed.