Composing a machine should error if name contains underscore

[Chris Johnston]

When composing a machine, if I under a name that contains an underscore I am allowed to click 'Compose machine', however, the name is changed to a name provided by MAAS. This is an unexpected behaviour and would be better if an error were provided showing that you can't compose a machine with an underscore.

2.5.2 (7523-ge4ecbd54d-0ubuntu1~18.04.1)

[Andres Rodriguez (andreserl)]

The solution should that the backend needs to validate that hostnames never use underscores.

[Lilyana Videnova (lilyanavidenova)]

I think we should disable the "Compose" button, similarly to how the "Save" button is disabled upon entering an underscore, as otherwise the user can submit the invalid value and would then see an error.

[Andres Rodriguez (andreserl)]

That’s a possibility, that said, this issue is really a backend issue!

[Chris Johnston (cjohnston)]

When using the CLI to compose a machine and specifying a hostname with an underscore the machine is assigned a random name. I would expect this to also return a message preventing the behaviour. Certainly seems like a backend issue.

[Newell Jensen (newell-jensen)]

https://code.launchpad.net/~newell-jensen/maas/+git/maas/+merge/367142

This branch uses ValidationSErvice.validateHostname for the validation and also adds unit tests as those were not originally added.