Sorbet Inline Generation Skill

Generate Sorbet type signatures using sig {} blocks directly in Ruby source files. Sorbet signatures are valid Ruby code that enable both static and runtime type checking.

Instructions

When generating Sorbet inline signatures, always follow these steps.

Copy this checklist and track your progress:

Sorbet Inline Generation Progress:
- [ ] Step 1: Analyze the Ruby source
- [ ] Step 2: Add Sorbet signatures
- [ ] Step 3: Eliminate `T.untyped` in signatures
- [ ] Step 4: Review and refine signatures
- [ ] Step 5: Validate signatures with Sorbet

Rules

• You MUST NOT run Ruby code of the project.
• You MUST NOT use T.untyped. Infer the proper type instead.
• You MUST NOT use T.unsafe - it bypasses type checking entirely.
• You MUST NOT use T.cast - it forces types without verification.
• 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 sig { } block syntax for method signatures.
• You MUST add extend T::Sig to classes/modules before using sig.
• You MUST focus on method signatures only. Skip local variables, intermediate expressions, and other non-method annotations.
• You MUST NOT use or generate .rbi files. This skill is for inline signatures only.
• You MUST preserve the existing # typed: sigil level if one exists. Do not upgrade or change strictness without explicit user consent.

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 existing # typed: sigil level at the top of the file.
• Note type parameters for generic classes.

2. Add Sorbet Signatures

Always perform this step.

1. First, check if the file already has a # typed: sigil at the top:

   • If sigil exists: Preserve the existing level. Do not change it without user consent.
   • If no sigil exists: Add # typed: true as a sensible default (allows gradual typing).

   Sigil levels (least to most strict): ignore < false < true < strict < strong

2. Add extend T::Sig to the class/module:

    class MyClass
      extend T::Sig
    end

3. Then add type signatures using sig {} blocks:

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:

# typed: true

class User
  extend T::Sig

  sig { returns(String) }
  attr_reader :name

  sig { returns(Integer) }
  attr_reader :age

  sig { params(name: String, age: Integer).void }
  def initialize(name, age)
    @name = name
    @age = age
  end

  sig { params(greeting: String).returns(String) }
  def greet(greeting)
    "#{greeting}, #{@name}!"
  end
end

• Focus on method and attribute signatures only
• See syntax.md for the full Sorbet syntax guide

3. Eliminate T.untyped in Signatures

Always perform this step.

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

4. Review and Refine Signatures

Always perform this step.

• Verify signatures are correct, coherent, and complete.
• Remove unnecessary T.untyped types.
• Ensure all methods and attributes have signatures.
• Fix any errors and repeat until signatures are correct.

5. Validate Signatures with Sorbet

Always perform this step.

Run Sorbet type checker to validate signatures:

srb tc

Or with bundle:

bundle exec srb tc

This checks:

• Signature syntax correctness
• Type consistency
• Method parameter/return type matching
• Instance variable initialization

Fix any errors reported and repeat until validation passes.

References

• syntax.md - Sorbet signature syntax guide
• sorbet_examples/ - Real-world Sorbet examples from production gems
• Sorbet documentation - Official Sorbet docs