generating-rbs-inline

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

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-Inline Generation Skill

Generate or update RBS-inline type annotations as comments directly in Ruby source files. Supports both full generation from scratch and partial updates for individual changed files. Unlike pure RBS which uses separate .rbs files, rbs-inline embeds type information as structured comments within Ruby code.

Instructions

When generating RBS-inline annotations, always follow these steps.

Copy this checklist and track your progress:

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

Rules

• 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 # @rbs comment syntax for inline annotations.
• You MUST NOT use regular RBS signatures and .rbs files in the project.
• 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-inline-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-inline-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. Add RBS-Inline Annotations

Always perform this step.

1. First, add the magic comment at the top of the Ruby file to enable rbs-inline processing:

   # rbs_inline: enabled
   

2. Then add type annotations as comments directly in the Ruby source file using rbs-inline syntax:

Example - Before:

class User
  attr_reader :name, :age

  def initialize(name, age)
    @name = name
    @age = age
  end

  def greet(greeting)
    "#{greeting}, #{@name}!"
  end
end

Example - After:

# rbs_inline: enabled

class User
  attr_reader :name #: String
  attr_reader :age #: Integer

  # @rbs name: String
  # @rbs age: Integer
  # @rbs return: void
  def initialize(name, age)
    @name = name
    @age = age
  end

  #: (String) -> String
  def greet(greeting)
    "#{greeting}, #{@name}!"
  end
end

• Follow RBS-inline syntax conventions strictly
  • See syntax.md for the full RBS-inline syntax guide
• Pay extra attention to Data and Struct types
  • See data-struct-support.md for Data and Struct handling

3. Eliminate untyped Types in Annotations

Always perform this step.

• Review all annotations and replace untyped with proper types.
• Use code context, method calls, and tests to infer types.
• Use untyped only as a last resort when type cannot be determined.

4. Review and Refine Annotations

Always perform this step.

• Verify annotations are correct, coherent, and complete.
• Remove unnecessary untyped types.
• Fix any errors and repeat until annotations are correct.

5. Validate Annotations

Always perform this step.

rbs-inline is a transpiler - it generates RBS files from inline annotations. Validation happens on the generated RBS output.

1. Generate RBS files from annotations:

   rbs-inline --output lib
   

   This generates .rbs files in sig/generated/ directory.

2. Validate the generated RBS files:

   rbs validate
   

   This checks syntax, name resolution, inheritance, and type applications.

3. Fix any errors in your inline annotations and repeat until validation passes.

6. Ensure Type Safety

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

Steep works on RBS files, not directly on inline annotations. The RBS files must be generated first (step 5).

1. Ensure RBS files are generated from annotations:

   rbs-inline --output lib
   

2. Run Steep type checker:

   steep check
   

3. Fix any errors reported by steep check.

   • Do not modify Steepfile to fix errors.
   • Fix the inline annotations in Ruby source files.
   • Regenerate RBS files and repeat until no errors.

References

• syntax.md - RBS-inline syntax guide
• data-struct-support.md - Data and Struct handling in rbs-inline
• examples/ - Real-world rbs-inline examples from production gems
• rbs-inline repository - Official rbs-inline gem