'NoneType' object is not iterable error is raised when syncing a manifest list

[lubosmj]

When I create a manifest list with the following manifests and push it to dockerhub:

#podman version 3.4.7

podman pull ghcr.io/pulp/test-fixture-1:manifest_a
podman pull ghcr.io/pulp/test-fixture-1:manifest_b
podman pull ghcr.io/pulp/test-fixture-1:manifest_c

podman manifest create ml

podman manifest add ml ghcr.io/pulp/test-fixture-1:manifest_a
podman manifest add ml ghcr.io/pulp/test-fixture-1:manifest_b
podman manifest add ml ghcr.io/pulp/test-fixture-1:manifest_c

podman manifest push ml docker.io/lubosmj/test

I receive a runtime error when trying to sync from the corresponding remote dockerhub repository:

pulp container remote create --name test --url https://registry-1.docker.io --upstream-name "lubosmj/test"
pulp container repository create --name test
pulp container repository sync --name test --remote test

Started background task /pulp/api/v3/tasks/020c95a3-c990-4a36-b121-c5c347c8212d/
...Error: Task /pulp/api/v3/tasks/020c95a3-c990-4a36-b121-c5c347c8212d/ failed: ''NoneType' object is not iterable'

pulp [494a2583824d4ada829d0f55f555347d]: pulpcore.tasking.pulpcore_worker:INFO: Task 020c95a3-c990-4a36-b121-c5c347c8212d failed ('NoneType' object is not iterable)
pulp [494a2583824d4ada829d0f55f555347d]: pulpcore.tasking.pulpcore_worker:INFO:   File "/home/vagrant/devel/pulpcore/pulpcore/tasking/pulpcore_worker.py", line 445, in _perform_task
    result = func(*args, **kwargs)
  File "/home/vagrant/devel/pulp_container/pulp_container/app/tasks/synchronize.py", line 41, in synchronize
    return dv.create()
  File "/home/vagrant/devel/pulpcore/pulpcore/plugin/stages/declarative_version.py", line 161, in create
    loop.run_until_complete(pipeline)
  File "/usr/lib64/python3.10/asyncio/base_events.py", line 646, in run_until_complete
    return future.result()
  File "/home/vagrant/devel/pulpcore/pulpcore/plugin/stages/api.py", line 225, in create_pipeline
    await asyncio.gather(*futures)
  File "/home/vagrant/devel/pulpcore/pulpcore/plugin/stages/api.py", line 43, in __call__
    await self.run()
  File "/home/vagrant/devel/pulp_container/pulp_container/app/tasks/sync_stages.py", line 188, in run 
    await self.handle_blobs(man_dc, content_data)
  File "/home/vagrant/devel/pulp_container/pulp_container/app/tasks/sync_stages.py", line 306, in handle_blobs
    for layer in content_data.get("layers") or content_data.get("fsLayers"):

[ipanova]

the sync pipeline logic probably does not account for the case when there is an empty manifest list ( you did not use --all during push.)

[lubosmj]

The manifest list should contain 3 manifests: https://hub.docker.com/repository/registry-1.docker.io/lubosmj/test/tags

[lubosmj]

There might be no manifests pushed along with the manifest list as I did not use the --all option: https://docs.podman.io/en/latest/markdown/podman-manifest-push.1.html#all

@ipanova, do we want to enable synchronization of "empty" (i.e., containing only metadata) manifest lists?

[ipanova]

yes, as long a json schema validation allows such and based on the specs i've checked, there is no enforcement of manifests array>=1

[ipanova]

ipanova
hey, i am looking back at this issue https://github.com/pulp/pulp_container/issues/882
and i think based on the traceback it has nothing to do with the empty manifests in the manifest list
it fails here https://github.com/pulp/pulp_container/blob/main/pulp_container/app/tasks/sync_stages.py#L188 because it went into the else condition  https://github.com/pulp/pulp_container/blob/main/pulp_container/app/tasks/sync_stages.py#L176
lmjachky
Yes
ipanova
because it did not find the mediatype?https://github.com/pulp/pulp_container/blob/main/pulp_container/app/tasks/sync_stages.py#L133
lmjachky
Because the media type for oci is unknown 
Yes
ipanova
so this is a dupe
of the other issue
you agree?
lmjachky
Ah, actually, you are right 
Yes, I agree 

@lubosmj will you close it as a dup of #883?