netplan crashes when there is an empty origin hint file

[Michael Vogt]

When there is an empty netplan origin hint file and one tries to write it will crash netplan:

qemu:ubuntu-core-20-64 .../tests/core/netplan-cfg# echo "" > /etc/netplan/90-snapd-conf.yaml
qemu:ubuntu-core-20-64 .../tests/core/netplan-cfg# netplan set --origin-hint 90-snapd-conf network.bridges.br54.dhcp4=true
Traceback (most recent call last):
  File "/usr/sbin/netplan", line 23, in <module>
    netplan.main()
  File "/usr/share/netplan/netplan/cli/core.py", line 50, in main
    self.run_command()
  File "/usr/share/netplan/netplan/cli/utils.py", line 310, in run_command
    self.func()
  File "/usr/share/netplan/netplan/cli/commands/set.py", line 53, in run
    self.run_command()
  File "/usr/share/netplan/netplan/cli/utils.py", line 310, in run_command
    self.func()
  File "/usr/share/netplan/netplan/cli/commands/set.py", line 106, in command_set
    self.write_file(subtree, hint + '.yaml', self.root_dir)
  File "/usr/share/netplan/netplan/cli/commands/set.py", line 156, in write_file
    new_tree = self.merge(config, set_tree)
  File "/usr/share/netplan/netplan/cli/commands/set.py", line 133, in merge
    if key in a:
TypeError: argument of type 'NoneType' is not iterable

[Michael Vogt (mvo)]

Fwiw, the same seems to happen if the origin file does not exist and a subtree is unset (I can file a different bug for this). E.g.:

"""
# netplan set --origin-hint 90-some-random-thing-not-on-disk network=null
Traceback (most recent call last):
  File "/usr/sbin/netplan", line 23, in <module>
    netplan.main()
  File "/usr/share/netplan/netplan/cli/core.py", line 50, in main
    self.run_command()
  File "/usr/share/netplan/netplan/cli/utils.py", line 310, in run_command
    self.func()
  File "/usr/share/netplan/netplan/cli/commands/set.py", line 53, in run
    self.run_command()
  File "/usr/share/netplan/netplan/cli/utils.py", line 310, in run_command
    self.func()
  File "/usr/share/netplan/netplan/cli/commands/set.py", line 106, in command_set
    self.write_file(subtree, hint + '.yaml', self.root_dir)
  File "/usr/share/netplan/netplan/cli/commands/set.py", line 176, in write_file
    raise Exception('Invalid input: {}'.format(set_tree))
Exception: Invalid input: {'network': None}
"""

[Lukas Märdian (slyon)]

I can confirm these issues and prepared a few reproducer testcases (for test_cli_get_set.py), let's try to get those resolved!

    def test_set_empty_hint_file(self):
        empty_file = os.path.join(self.workdir.name, 'etc', 'netplan', '00-empty.yaml')
        open(empty_file, 'w').close() # touch empty file
        self._set(['ethernets.eth0.dhcp4=true', '--origin-hint=00-empty'])
        print(empty_file, flush=True)
        self.assertTrue(os.path.isfile(empty_file))
        with open(empty_file, 'r') as f:
            self.assertIn('network:\n ethernets:\n eth0:\n dhcp4: true', f.read())

    def test_set_network_null_hint(self):
        not_a_file = os.path.join(self.workdir.name, 'etc', 'netplan', '00-no-exist.yaml')
        self._set(['network=null', '--origin-hint=00-no-exist'])
        self.assertFalse(os.path.isfile(not_a_file))

    def test_set_network_null(self):
        not_a_file = os.path.join(self.workdir.name, 'etc', 'netplan', '00-no-exist.yaml')
        self._set(['network=null'])
        self.assertFalse(os.path.isfile(not_a_file))

[Lukas Märdian (slyon)]

FTR: This is being worked on here: https://github.com/canonical/netplan/pull/246

[Lukas Märdian (slyon)]

I'm marking this a duplicate of LP: #1946957 as it is the same class of errors and fixed in the same upstream PR.