"Bad artifact coordinates ..., expected format is <groupId>:<artifactId>:<version>"

Server log

Caused by: java.lang.IllegalArgumentException: Bad artifact coordinates gson, expected format is <groupId>:<artifactId>[:<extension>[:<classifier>]]:<version>

What it means

The server downloads the libraries listed in libraries before loading the plugin. One entry is not a full Maven coordinate, so the plugin fails to load.

What causes it

An entry in libraries is missing the group, artifact or version part.

How to fix it

Before

libraries:
  - gson

After

libraries:
  - com.google.code.gson:gson:2.11.0

Copy the coordinate from Maven Central. The format is group:artifact:version.

Check the whole file. Paste your plugin.yml or drop the plugin jar into Permistry. It finds this and about 40 other problems, and explains each one in plain words. It runs in your browser and nothing is uploaded.

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