fix: handle loading and parsing errors when loading themes

[rpocklin]

Description

There are multiple conditions where a custom theme will fail to load eg.

1. If the file extension does not end in .json
2. If the file is not found
3. If there is any other error attempting to fetch the file from network
4. If the file is not a valid JSON file format

Currently only (1), (2) and (3) are handled by returning the default owncloud extension.

This fix adds error handling for (4) and also refactors the code a little. Currently (4) will break the application with:

web-runtime.js:5504 SyntaxError: Unexpected token d in JSON at position 584

as there is no catch around the json parsing.

With the fix, it will show the following on the console:

web-runtime.js:5262 Failed to load theme 'themes/aarnet/theme.json' is not a valid JSON file, using default theme.

This fix also logs a console error that a custom theme load failed and the default theme is going to be used (I personally found it confusing as it failed silently to load the theme and I was unsure what had happened.)

How Has This Been Tested?

Tested manually in the browser and have added / updated unit tests.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Technical debt
• Tests

[update-docs]

Thanks for opening this pull request! The maintainers of this repository would appreciate it if you would create a changelog item based on your changes.

[ownclouders]

Results for oC10SharingInternalGroupsSharingIndicator https://drone.owncloud.com/owncloud/web/18261/24/1
💥 The acceptance tests pipeline failed. The build has been cancelled.

[kulmann]

Nice improvement for admins, love it! 💪🏻

[kulmann]

I restarted CI, since the failing test was a random failure... we have a lot of those recently and currently work towards fixing it, sorry.

[sonarcloud]

SonarCloud Quality Gate failed.   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

32.7% Coverage
4.0% Duplication

[ownclouders]

Results for oC10SharingInternalUsersSharingIndicator https://drone.owncloud.com/owncloud/web/18267/28/1
The following scenarios passed on retry:

• webUISharingInternalUsersToRootSharingIndicator/shareWithUsers.feature:98

[ownclouders]

Results for oC10XGAPortrait1 https://drone.owncloud.com/owncloud/web/18267/42/1
The following scenarios passed on retry:

• webUIDeleteFilesFolders/deleteFilesFolders.feature:59