Allows empty links in YAML configuration file.

[tristan0x]

Fixed TypeError: 'NoneType' object is not iterable issue when service declares an empty list of links.
Fixes #1086

Signed-off-by: Tristan Carel tristan@cogniteev.com

[aanand]

Thanks, but I'd rather not allow links to be None. It'd be better to throw a helpful error.

[tristan0x]

Yet, this is valid YAML:

console:
   image: busybox:latest
   links:
   command: /bin/sleep 300

In that case, links are None. It is what the yaml library returns. But it still means empty list of links.

Do you expect compose to throw an helpful error for such config?

If you don't, here is a patch proposal!
I understand you prefer a clean model in compose.project.Project class, without stuff like None links. So what about fixing the YAML returned by compose.cli.command.Command.get_config member method by replacing None by [] for a bunch of keys:

• links
• external_links
• ports
• volumes
• volumes_from
• env_file

[ghost]

@tristan0x: Why was this closed without merging?

I often run into this "NoneType is not iterable" problem when I forget to remove an empty YAML key, and your change seemed like a step in the right direction. If anything, I think your change should be expanded to the other YAML keys (as you suggest in your Mar 12 comment).

👍 for this pr

[tristan0x]

@mgoelzer : This issue is part of something bigger which is configuration validation. Please see #129
Thank anyway for your support :)