package_names

Use lowercase_with_underscores for package names.

From the Pubspec format description:

DO use lowercase_with_underscores for package names.

Package names should be all lowercase, with underscores to separate words, just_like_this. Use only basic Latin letters and Arabic digits: [a-z0-9_]. Also, make sure the name is a valid Dart identifier -- that it doesn't start with digits and isn't a reserved word.

To enable the package_names rule, add package_names under linter > rules in your analysis_options.yaml file:

linter:
  rules:
    - package_names

If you're instead using the YAML map syntax to configure linter rules, add package_names: true under linter > rules:

linter:
  rules:
    package_names: true