Allow including and excluding files name patterns on a per rule basis.

We'd like to have a way to enable and disable rules based on the file name of the swift file.

Solutions we considered

Child/parent configs seem like it's for refining the rules for the whole project/folder, not on a per-file basis. It also only seems to allow a one-to-one relationship.

Nested configurations only apply to a whole folder but sometimes there's rules that should only be applied to some files in the folder. For example, a view and view controller in the same folder but there's a rule that should only be enabled for the view controller.

Updating every rule to allow passing a file pattern seems like it'd be a huge and and it'd conflict with some existing rules that already have parameters for include and exclude.

Suggested solution

I'd like the propose the idea to have a config file that can reference multiple sub-config files. The root config file would contain all the default settings that are used for the matched files. The sub-configs would then further refine the settings allowing including or excluding files that it's rules/settings applied to.

Example

.swiftlint.yml

opt_in_rules:
  - force_unwrapping
sub_configs:
  - .swiftlint-tests.yml

.swiftlint-tests.yml

disabled_rules:
  - force_unwrapping
sub_configs:
  - .swiftlint-spec.yml
  - .swiftlint-mock.yml
included:
  - **/Tests

.swiftlint-spec.yml

disabled_rules:
  - function_body_length
included:
  - *.spec.swift

.swiftlint-mock.yml

custom_rules:
  my_custom_rule:
    ...
included:
  - *+Mock.swift

If it was linting the following files, the following would occur.

• Foo/Sources/Foo.swift
  • .swiftlint.yml would enable force_unwrapping
• Foo/Tests/Foo.spec.swift
  • .swiftlint.yml would enable force_unwrapping
  • .swiftlint-tests.yml would match the file name and disable force_unwrapping
  • .swiftlint-spec.yml would match the file name and disable function_body_length
• Foo/Tests/FooService+Mock.swift
  • .swiftlint.yml would enable force_unwrapping
  • .swiftlint-tests.yml would match the file name and disable force_unwrapping
  • .swiftlint-mock.yml would match the file name and enable my_custom_rule
• Bar/Source/BarService+Mock.swift
  • .swiftlint.yml would enable force_unwrapping
  • .swiftlint-tests.yml would not match the file name
  • .swiftlint-mock.yml would not be used

Begin with the proposed .swiftlint.yml and sub-config examples, then compare them with current configuration behavior. Verify how included and excluded patterns should compose for the listed Foo and Bar file paths; done means the per-rule configuration works consistently for those cases and existing configuration behavior remains intact.