The feature I’m describing below has been available since Ansible 2.6, but got a bugfix in v2.6.2 and another (minor) one in v2.7.
To see a solution for older versions, see Paul’s answer.
defaults/main/
Instead of creating defaults/main.yml, create a directory — defaults/main/ — and place all YAML files in there.
defaults/main.yml→defaults/main/*.yml
Ansible will load any *.yml file inside that directory, so you can name your files like roles/my-role/defaults/main/{1,2}.yml.
Furthermore, it’s even possible to create sub-directories like roles/my-role/defaults/main/subdir_1/foo.yml.
Note, the old file — defaults/main.yml — must not exist. See this Github comment.
vars/main/
By the way, the above solution also works for vars/:
vars/main.yml→vars/main/*.yml
further details
The feature has been introduced in v2.6 — git commit, Pull Request, main Github issue.
There have been two bugfixes:
- v2.7 fix: git commit, Pull Request — backported to v2.6.2: commit, Pull Request
- v2.7 fix: git commit, Pull Request, bug discussion