How to rename variables while maintaining compatibility?

[34j]

I would like to follow #1940 and change the variable name full_name that was already in use to user_name, but I don't know the correct way to do this while maintaining compatibility (i.e. avoiding to retyping the name when copier update). Perhaps something like this?

full_name:
  type: str
  when: false
  default: ""

user_name:
  type: str
  default: {{ full_name }}

[sisp]

I think you could use a migration similar to how it's done in this test, but you would change the answer variable instead of the value. Make sure to update all variable occurrences in your template accordingly and set the version field in the migration config to your template's next release version. Unlike in the test case, force reading and writing the answers file data as UTF-8 for best cross-OS compatibility (see #1970).