Determine best location for role dependencies

[jsf9k]

💡 Summary

We should determine whether all role dependencies should be listed in meta/requirements.yml or both meta/requirements.yml and meta/main.yml.

Motivation and context

Ansible Galaxy currently allows role dependencies to be listed in both meta/requirements.yml and meta/main.yml. The former allows for both collection and role dependencies, while the latter allows for only role dependencies. A key difference is that dependencies listed in meta/main.yml are installed before the role is installed, while the dependencies listed in meta/requirements.yml are made available to the role but not automatically installed.

Right now we are defaulting to listing dependencies in meta/main.yml, and listing dependencies in meta/requirements.yml in cases where

• The installation of a dependency is conditional based upon the values on role variables, or
• The dependency's role variables must be assigned dynamic values.

One can imagine a world in which all dependencies are listed in meta/requirements.yml and we manually install the dependencies in the role tasks for maximum control and flexibility. It is currently unclear if this is The Way Forward, so we should keep an eye on ansible-galaxy changes and recommended best practices until the situation becomes clearer.

[jsf9k]

Note also that it is possible to list both collections and roles in meta/requirements.yml, but unfortunately ansible-galaxy attempts to naively merge the dependencies listed in meta/main.yml with those listed in meta/requirements.yml. That means that both sets of dependencies must be arrays, so as long as we are using both files we can only list roles in meta/requirements.yml. This is one argument for moving wholesale to meta/requirements.yml.

[jsf9k]

Also note that an ansible-galaxy requirements file allows for including one such file from another. If we defined all dependencies in the meta/requirements.yml file then we should be able to include that file from molecule/default/requirements.yml and avoid keeping track of role dependencies in two places. DRYness is next to godliness.

[jsf9k]

There is a fly in the ointment: ansible/proposals#57 (comment)

It appears that collections are not really supported as dependencies in meta/requirements.yml, although ansible-lint thinks so. 😞

This causes us a major problem, since in some cases ansible-lint insists that we list collection dependencies for modules, yet Ansible stubbornly refuses to support this. See, for example, this failing build.

[jsf9k]

ansible/ansible#76030 is also of note, particularly ansible/ansible#76030 (comment).