Pulp

The "_artifacts" field is rather difficult to use from a user perspective, and is also over-generalized. Nearly all currently existing Pulp 3 plugins have a single have a single artifact per content unit, and carry around boilerplate code to replace the "_artifacts" (plural) serializer field with a singular version, in order to avoid the usability issues that comes with it.

This boilerplate is not ideal, and errors found in it (such as [0] )must be made against many, many plugins.

There are also additional common invariants, such as Content without any Artifacts, which should be handled in a more explicit way without any plugin writer boilerplate.

To fix this, we propose the following changes to the plugin API:

• The current "ContentSerializer" will be renamed to MultiArtifactContentSerializer
• A new "SingleArtifactContentSerializer" will be defined, which has an "_artifact" field, which lists a single artifact
• A new "NoArtifactContentSerializer" will be defined, which lacks any field related to Artifacts

Plugin writers will inherit their own content serializers from the one most closely matching their needs.

The one used in plugin_template by default will be the SingleArtifactContentSerializer, with a FIXME instruction added.

This should also be documented in the plugin writer docs.

[0] https://pulp.plan.io/issues/4340