duplicate_rule

The rule '{0}' is already enabled and doesn't need to be enabled again.

The analyzer produces this diagnostic when the same lint rule is listed more than once in the linter/rules section.

The following code produces this diagnostic because the lint rule avoid_print appears twice in the list of enabled rules:

// %uri="analysis_options.yaml"
linter:
  rules:
    - avoid_print
    - avoid_print

Remove the duplicates:

// %uri="analysis_options.yaml"
linter:
  rules:
    - avoid_print