Attached Files:

• Log outputs
• Full datapack (no errors)

Issue:

When creating a world with custom features in a datapack, the world fails to load with the following fatal exception (variations on the hex at the end depending on file name/data): (see log.txt/log4.txt for more log information)

java.lang.IllegalArgumentException: value already present: cio@4b74a4d

To recreate:

Simply add a json error into a configured feature file to recreate this issue.

Solution:

The exception above is caused by a configured feature file. For example, if I misspell something (like "bolished_pasalt") in the file, the above error (or similar) will appear. This is different from the custom biomes or worldgen settings, which will output an error telling me what is wrong in the json (example: key Name missing from dict). Fixing the json will get rid of the exception.

Fix:

I believe the fix for this issue would be implementing error handling for the configured features. For some reason they aren't getting the same error handling as the rest of the files.

I have seen other open issues with this problem but I don't think they
know the reason why the issue is occurring. I added this issue to hopefully offer a solution.