feat(lint): add multi-contract-file rule

[milosdjurica]

Added a new linting rule that checks for multiple contract-like items (contracts, abstract contracts, interfaces and libraries) per .sol file

Motivation

Enforce best practice.

Solution

I have some doubts regarding this, would like to hear your opinion.

1. Should the rule skip interfaces and libraries and count only contracts?
2. Should the rule show linting note for every contract-like item in the file, or only one time per file is enough?

My solution count interfaces and libraries too, and it shows linting note only once per file. Let me know if you want something to be changed :)

PR Checklist

• Added Tests
• Added Documentation
• Breaking changes

Keep up the good work guys, cheers!

[0xrusowsky]

@milosdjurica first of all thanks for the PR and the initiative, we love new contributions to forge's linter!

i think the idea overall makes sense, however imo we can improve it.

1. i'd like each contract to be flagged, not just the 2nd one
2. imo it would make sense to add a custom config for this lint, so that users can decide if they want to allow interfaces and/or libs in the same file. To do so, you'd want to modify the LinterConfig to have a dedicated config for this lint. If we do that, i think we then want to create a new intermediate struct that group all lint configs (i.e. the pre-existing mixed_case_exceptions + your newly introduced config)

lmk if this seems reasonable and if u have any doubts regarding impl

[milosdjurica]

@milosdjurica first of all thanks for the PR and the initiative, we love new contributions to forge's linter!

i think the idea overall makes sense, however imo we can improve it.

1. i'd like each contract to be flagged, not just the 2nd one
2. imo it would make sense to add a custom config for this lint, so that users can decide if they want to allow interfaces and/or libs in the same file. To do so, you'd want to modify the LinterConfig to have a dedicated config for this lint. If we do that, i think we then want to create a new intermediate struct that group all lint configs (i.e. the pre-existing mixed_case_exceptions + your newly introduced config)

lmk if this seems reasonable and if u have any doubts regarding impl

Sounds great, I like it! Will look to implement it ASAP :)
Thanks for the response!