generating-rbs

name	generating-rbs
description	Generates or updates RBS type signatures in separate .rbs files. Triggers when creating, updating, or maintaining type signatures for Ruby source files. Use for sig/**/*.rbs files (Steep/RBS), not inline comments.

Defaults (ruby-rails plugin)

• Toolchain: mise — use mise exec -- when the project uses mise
• Ruby: 4.0.0+ unless the project pins otherwise
• Commands: Prefer mise exec -- bundle exec over bare bundle exec when Gemfile is present
• Pairing: Use generating-rbs-inline vs generating-rbs (and Sorbet inline vs RBI) based on project convention — never mix systems in one file

RBS Generate Skill

Generate or update pure RBS signatures for Ruby source files. Supports both full generation from scratch and partial updates for individual changed files. Does not handle RBS-inline signatures.

Instructions

When generating RBS signatures from scratch, always follow these steps.

Copy this checklist and track your progress:

RBS Generation Progress:
- [ ] Step 1: Analyze the Ruby source
- [ ] Step 2: Generate RBS signatures
- [ ] Step 3: Eliminate `untyped` types in generated signatures
- [ ] Step 4: Review and refine RBS signatures
- [ ] Step 5: Validate shape of RBS signatures
- [ ] Step 6: Ensure type safety (only if steep is configured)

Rules

There are several rules that you MUST follow while performing this skill:

• You MUST not run Ruby code of the project.
• You MUST not use untyped. Infer the proper type instead.
• You MUST ask the user to provide more details if something is not clear.
• You MUST prepend any command with bundle exec if the project has Gemfile.
• You MUST use the tracking file when processing multiple files to ensure no files are missed.

Multi-File Processing

When processing multiple Ruby files, create a tracking file to ensure all files are covered:

1. Create tracking file .rbs-generation-todo.tmp:

   [ ] app/models/user.rb
   [ ] app/models/post.rb
   [ ] app/services/auth_service.rb

1. Process files one by one:

   • Take the next pending [ ] entry
   • Complete all steps (1-6) for that file
   • Mark as processed [x]
   • Save the tracking file
   • Continue to next pending entry

2. Cleanup: Remove the tracking file after all files are processed:

   rm .rbs-generation-todo.tmp
   

If interrupted, the tracking file allows resuming from where you left off.

1. Analyze the Ruby Source

Always perform this step.

Read and understand the Ruby source file:

• Identify all classes, modules, methods, constants and instance variables.
• Note inheritance, module inclusion and definitions based on metaprogramming.
• Note visibility modifiers - public, private, protected.
• Note type parameters for generic classes.

2. Generate RBS Signatures

Always perform this step.

• Create necessary .rbs files for the target Ruby file.
• Place generated RBS files in sig/ directory mirroring Ruby source structure.
• You need to strongly follow RBS syntax conventions to describe types for all declarations
  • See syntax.md for the full list of RBS types. Double-check it in tricky cases.
• Take inspiration from RBS signature examples
  • See rbs_by_example.md for short list of RBS signatures examples
  • See core for RBS signatures of Ruby core library
  • See stdlib for RBS signatures of Ruby standard library
  • Pay extra attention to Data and Struct types. See data_and_struct.md for handling guide
  • See gem_rbs_collection for RBS signature examples of different Ruby libraries. This link contains only RBS files, Ruby sources are not included.

3. Eliminate untyped types in generated signatures

Always perform this step.

• Go through all generated signatures and replace untyped with the proper type.
• Use assumptions and calls examples in Ruby code and tests to infer the proper type.
• If you cannot infer the proper type, leave it as untyped.
  • It is a last resort, use it only when there is no other option.

4. Review and refine RBS signatures

Always perform this step.

• Take a look at the generated signatures and make sure they are correct, coherent and complete.
• Try to get rid of any unnecessary untyped types.
• If you find any errors, please fix them and repeat the process until there are no errors.

5. Validate shape of RBS signatures

Always perform this step.

• Run rbs validate to verify that existing and new .rbs files are internally consistent. It will check syntax, name resolution, inheritance, method overloading, type variables, etc.
• Fix any errors reported by rbs validate and repeat the process until there are no errors.

6. Ensure type safety of RBS signatures

Perform this step ONLY if the project Gemfile includes steep gem AND the project has Steepfile.

• Run steep check to verify that generated RBS signatures are type safe.
• Fix any errors reported by steep check and repeat the process until there are no errors.
  • Do not modify Steepfile in an attempt to fix errors.
• Roll back to step 4 if you fixed any errors reported by steep check.

References

• syntax.md - The full list of RBS types and syntax
• rbs_by_example.md - Short list of RBS signatures examples
• core - RBS signatures of Ruby core library
• stdlib - RBS signatures of Ruby standard library
• data_and_struct.md - Explanation on Data and Struct types handling