Snapcraft adds `command-chain` to `assumes` when an app or hook uses `command-chain`, and `snapd2.74` when an app uses `success-exit-status`. If the project already declared the same feature, the generated `snap.yaml` listed it twice, and the store rejects the upload: ``` lint-snap-v2:snap_schema Error found while validating snap.json::$.assumes: ['command-chain', 'command-chain'] has non-unique elements ``` The declared and computed values are now combined as a set before sorting, so each feature is listed once. Fixes #4931 --- - [x] I've followed the [contribution guidelines](https://github.com/canonical/snapcraft/blob/main/CONTRIBUTING.md). - [x] I've signed the [CLA](http://www.ubuntu.com/legal/contributors/). - [x] I've successfully run `make lint && make test`. - [ ] I've added or updated any relevant documentation. - [ ] In documents I changed, I [added a meta description](https://canonical-starflow.readthedocs-hosted.com/how-to/add-a-page-meta-description/) if one was missing. - [ ] I've updated the relevant release notes.