Does Ansible dynamic inventory plugin for AWS EC2 allow the character - when naming groups?
From what I see, it changes hyphens (-) to underscores (_) when creating the graph of the inventory.
For example,
groups:
test-group: "'condition'"
is being represented as
|--@os_cluster:
| |--ip-10-0-0-00.az.example.com
when using ansible-inventory.
Group names should follow the same guidelines as Creating valid variable names.
Source: Inventory basics: formats, hosts, and groups
Then in the linked page:
Not all strings are valid Ansible variable names. A variable name can only include letters, numbers, and underscores.
Source: Creating valid variable names
So, indeed, group names cannot contain hyphens, and this is why Ansible replaces non valid characters by underscores in your group names.