yaml.constructor.ConstructorError: could not determine a constructor for the tag '!ExtractedMetadata'

[Alan Pope 🍺🐧🐱 🦄]

I am building a snap using SNAPCRAFT_CONTAINER_BUILDS to 1.

I have seen this error occur a lot, and usually if I re-run or clean, it goes away, but it's quite frustrating to keep getting it.

==2.35', 'console_scripts', 'snapcraft')()
  File "/snap/snapcraft/794/usr/lib/python3.6/site-packages/pkg_resources/__init__.py", line 565, in load_entry_point
    return get_distribution(dist).load_entry_point(group, name)
  File "/snap/snapcraft/794/usr/lib/python3.6/site-packages/pkg_resources/__init__.py", line 2631, in load_entry_point
    return ep.load()
  File "/snap/snapcraft/794/usr/lib/python3.6/site-packages/pkg_resources/__init__.py", line 2291, in load
    return self.resolve()
  File "/snap/snapcraft/794/usr/lib/python3.6/site-packages/pkg_resources/__init__.py", line 2297, in resolve
    module = __import__(self.module_name, fromlist=['__name__'], level=0)
  File "/snap/snapcraft/794/lib/python3.6/site-packages/snapcraft/cli/__main__.py", line 19, in <module>
    run(prog_name='snapcraft')
  File "/snap/snapcraft/794/lib/python3.6/site-packages/click/core.py", line 722, in __call__
    return self.main(*args, **kwargs)
  File "/snap/snapcraft/794/lib/python3.6/site-packages/click/core.py", line 697, in main
    rv = self.invoke(ctx)
  File "/snap/snapcraft/794/lib/python3.6/site-packages/click/core.py", line 1066, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/snap/snapcraft/794/lib/python3.6/site-packages/click/core.py", line 895, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/snap/snapcraft/794/lib/python3.6/site-packages/click/core.py", line 535, in invoke
    return callback(*args, **kwargs)
  File "/snap/snapcraft/794/lib/python3.6/site-packages/snapcraft/cli/lifecycle.py", line 140, in snap
    project_options, directory=directory, output=output)
  File "/snap/snapcraft/794/lib/python3.6/site-packages/snapcraft/internal/lifecycle/_packer.py", line 45, in snap
    execute('prime', project_options)
  File "/snap/snapcraft/794/lib/python3.6/site-packages/snapcraft/internal/lifecycle/_runner.py", line 80, in execute
    _Executor(config, project_options).run(step, part_names)
  File "/snap/snapcraft/794/lib/python3.6/site-packages/snapcraft/internal/lifecycle/_runner.py", line 138, in __init__
    self._steps_run = self._init_run_states()
  File "/snap/snapcraft/794/lib/python3.6/site-packages/snapcraft/internal/lifecycle/_runner.py", line 146, in _init_run_states
    dirty_report = part.get_dirty_report(step)
  File "/snap/snapcraft/794/lib/python3.6/site-packages/snapcraft/internal/pluginhandler/__init__.py", line 171, in get_dirty_report
    state = states.get_state(self.plugin.statedir, step)
  File "/snap/snapcraft/794/lib/python3.6/site-packages/snapcraft/internal/states/_state.py", line 99, in get_state
    state = yaml.load(f.read())
  File "/snap/snapcraft/794/lib/python3.6/site-packages/yaml/__init__.py", line 72, in load
    return loader.get_single_data()
  File "/snap/snapcraft/794/lib/python3.6/site-packages/yaml/constructor.py", line 37, in get_single_data
    return self.construct_document(node)
  File "/snap/snapcraft/794/lib/python3.6/site-packages/yaml/constructor.py", line 46, in construct_document
    for dummy in generator:
  File "/snap/snapcraft/794/lib/python3.6/site-packages/yaml/constructor.py", line 408, in construct_yaml_object
    state = self.construct_mapping(node)
  File "/snap/snapcraft/794/lib/python3.6/site-packages/yaml/constructor.py", line 204, in construct_mapping
    return super().construct_mapping(node, deep=deep)
  File "/snap/snapcraft/794/lib/python3.6/site-packages/yaml/constructor.py", line 129, in construct_mapping
    value = self.construct_object(value_node, deep=deep)
  File "/snap/snapcraft/794/lib/python3.6/site-packages/yaml/constructor.py", line 86, in construct_object
    data = constructor(self, node)
  File "/snap/snapcraft/794/lib/python3.6/site-packages/snapcraft/__init__.py", line 445, in dict_constructor
    return OrderedDict(loader.construct_pairs(node))
  File "/snap/snapcraft/794/lib/python3.6/site-packages/yaml/constructor.py", line 141, in construct_pairs
    value = self.construct_object(value_node, deep=deep)
  File "/snap/snapcraft/794/lib/python3.6/site-packages/yaml/constructor.py", line 86, in construct_object
    data = constructor(self, node)
  File "/snap/snapcraft/794/lib/python3.6/site-packages/yaml/constructor.py", line 414, in construct_undefined
    node.start_mark)
yaml.constructor.ConstructorError: could not determine a constructor for the tag '!ExtractedMetadata'
  in "<unicode string>", line 62, column 13:
      metadata: !ExtractedMetadata
                ^
Stopping local:snapcraft-dolphin-emu

[Cris Dywan (kalikiana)]

Can you provide a snapcraft.yaml or repo of a project that triggers this?

[Alan Pope 🍺🐧🐱 🦄 (popey)]

http://paste.ubuntu.com/26346626/
Here you go. The mbedtls part always needs a "sudo rm -rf parts/"

[Kyle Fazzari (kyrofa)]

Hey Alan, from the log it seems that you built this snap using a newer snapcraft (perhaps edge) and then started working in the same dirty tree on snapcraft v2.35. Is that correct? The state tracking has changed a bit in newer snapcrafts in a way that older snapcrafts don't understand. If you need to switch back and forth, you'll probably need to clean until the newer stuff is actually released.

[Alan Pope 🍺🐧🐱 🦄 (popey)]

Nope, ran the snapcraft command twice in a row on the same machine, no changes in between.

[Kyle Fazzari (kyrofa)]

Revision 794 is v2.35. ExtractedMetadata wasn't introduced until v2.38. How is that possible?

[Alan Pope 🍺🐧🐱 🦄 (popey)]

I'm doing container builds. The container uses apt.

[Kyle Fazzari (kyrofa)]

And you have the snapcraft snap from stable installed on your host? Christian, shouldn't it be injecting the same snap into the container?

[Kyle Fazzari (kyrofa)]

Well, wait. In apt Snapcraft is also 2.35. What snapcraft do you have on your host?

[Alan Pope 🍺🐧🐱 🦄 (popey)]

Exactly! My mistake, the container doesn't use apt, it uses the snap, but the snap is stable, and my host is tracking edge

Host:-

installed: 2.38+git3.af6551a (1021) 53MB classic

Container:-

root@snapcraft-backslide:~# which snapcraft
/snap/bin/snapcraft
root@snapcraft-backslide:~# snap list
Name Version Rev Developer Notes
core 16-2.30 3748 canonical core
snapcraft 2.35 794 canonical classic

[Kyle Fazzari (kyrofa)]

Okay, that's the problem. Christian, can you take a look at this when you're able? Something seems wrong with the injection-- we should be injecting the rev being used on the host, right?

[Alan Pope 🍺🐧🐱 🦄 (popey)]

Uh. I just did it again and now I have 2.38? Did you do something in the interim 17 minutes?

root@snapcraft-orbitdb-cli:~# snap list
No snaps are installed yet. Try "snap install hello-world".
root@snapcraft-orbitdb-cli:~# snap list
Name Version Rev Developer Notes
core 16-2.30 3748 canonical core
snapcraft 2.38+git3.af6551a 1021 canonical classic

[Cris Dywan (kalikiana)]

Can you clarify if you used `snapcraft clean` or `lxc delete` in-between to remove the container?

Snapcraft doesn't update snaps in the container automatically once the container has been created and it doesn't change the channel after the fact either - *unless* you do an explicit `snapcraft refresh`.

[Alan Pope 🍺🐧🐱 🦄 (popey)]

I definitely didn't do lxc delete, and don't believe I did snapcraft clean.

[Kyle Fazzari (kyrofa)]

A fix has been proposed here: https://github.com/snapcore/snapcraft/pull/1865