Building classic snap without core snap installed succeeds, but creates snap that doesn't run

[Kyle Fazzari]

Using the 2.39.2 deb, building a classic snap without the core snap installed results in:

Priming python3
Traceback (most recent call last):
  File "/usr/bin/snapcraft", line 9, in <module>
    load_entry_point('snapcraft==2.39.3', 'console_scripts', 'snapcraft')()
  File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 542, in load_entry_point
    return get_distribution(dist).load_entry_point(group, name)
  File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 2569, in load_entry_point
    return ep.load()
  File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 2229, in load
    return self.resolve()
  File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 2235, in resolve
    module = __import__(self.module_name, fromlist=['__name__'], level=0)
  File "/usr/lib/python3/dist-packages/snapcraft/cli/__main__.py", line 43, in <module>
    run(prog_name='snapcraft')
  File "/usr/lib/python3/dist-packages/click/core.py", line 716, in __call__
    return self.main(*args, **kwargs)
  File "/usr/lib/python3/dist-packages/click/core.py", line 696, in main
    rv = self.invoke(ctx)
  File "/usr/lib/python3/dist-packages/click/core.py", line 1037, in invoke
    return Command.invoke(self, ctx)
  File "/usr/lib/python3/dist-packages/click/core.py", line 889, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/usr/lib/python3/dist-packages/click/core.py", line 534, in invoke
    return callback(*args, **kwargs)
  File "/usr/lib/python3/dist-packages/click/decorators.py", line 17, in new_func
    return f(get_current_context(), *args, **kwargs)
  File "/usr/lib/python3/dist-packages/snapcraft/cli/_runner.py", line 72, in run
    ctx.forward(lifecyclecli.commands['snap'])
  File "/usr/lib/python3/dist-packages/click/core.py", line 552, in forward
    return self.invoke(cmd, **kwargs)
  File "/usr/lib/python3/dist-packages/click/core.py", line 534, in invoke
    return callback(*args, **kwargs)
  File "/usr/lib/python3/dist-packages/snapcraft/cli/lifecycle.py", line 139, in snap
    project_options, directory=directory, output=output)
  File "/usr/lib/python3/dist-packages/snapcraft/internal/lifecycle/_packer.py", line 46, in snap
    execute('prime', project_options)
  File "/usr/lib/python3/dist-packages/snapcraft/internal/lifecycle/_runner.py", line 79, in execute
    _Executor(config, project_options).run(step, part_names)
  File "/usr/lib/python3/dist-packages/snapcraft/internal/lifecycle/_runner.py", line 185, in run
    self._run_step(step, part, part_names)
  File "/usr/lib/python3/dist-packages/snapcraft/internal/lifecycle/_runner.py", line 222, in _run_step
    getattr(part, step)()
  File "/usr/lib/python3/dist-packages/snapcraft/internal/pluginhandler/__init__.py", line 578, in prime
    elf_patcher.patch(elf_file=elf_file)
  File "/usr/lib/python3/dist-packages/snapcraft/internal/elf.py", line 392, in patch
    elf_file_path=elf_file.path)
  File "/usr/lib/python3/dist-packages/snapcraft/internal/elf.py", line 297, in wrapper
    return f(*args, **kwargs)
  File "/usr/lib/python3/dist-packages/snapcraft/internal/elf.py", line 407, in _run_patchelf
    subprocess.check_call(cmd)
  File "/usr/lib/python3.5/subprocess.py", line 576, in check_call
    retcode = call(*popenargs, **kwargs)
  File "/usr/lib/python3.5/subprocess.py", line 557, in call
    with Popen(*popenargs, **kwargs) as p:
  File "/usr/lib/python3.5/subprocess.py", line 947, in __init__
    restore_signals, start_new_session)
  File "/usr/lib/python3.5/subprocess.py", line 1490, in _execute_child
    restore_signals, start_new_session, preexec_fn)
TypeError: Can't convert 'NoneType' object to str implicitly

This traces back to project_options.get_core_dynamic_linker() returning None in the pluginhandler.

[Sergio Schvezov (sergiusens)]

Kyle, this is solved with the latest 2.40 (to be released) version, right?

[Kyle Fazzari (kyrofa)]

Indeed, the traceback no longer occurs. However, there's still a behavior change when compared to 2.35, which errors out with "classic confinement requires the core snap to be installed. Install it by running `snap install core`." 2.40 just happily uses '/snap/core/current/lib64/ld-linux-x86-64.so.2'. Is that desired? I'll set back to New just in case, but if this is working as desired, feel free to set to Fix Committed.

[Kyle Fazzari (kyrofa)]

Turns out this is _not_ desired behavior, so using this bug to track the fix.