Module: Docscribe::Infer::Returns

Defined in:
lib/docscribe/infer/returns.rb

Overview

Return type inference and rescue-conditional return extraction.

Class Method Summary collapse

Class Method Details

.infer_return_type(method_source) ⇒ String

Note:

module_function: when included, also defines #infer_return_type (instance visibility: private)

Infer a return type from a full method definition source string.

The source must parse to a ‘:def` or `:defs` node. If parsing fails or inference is uncertain, the fallback type is returned.

Parameters:

  • method_source (String, nil) —

    full method definition source

Returns:

  • (String)

Raises:

  • (Parser::SyntaxError) 


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# File 'lib/docscribe/infer/returns.rb', line 18

def infer_return_type(method_source)
  return FALLBACK_TYPE if method_source.nil? || method_source.strip.empty?

  buffer = Parser::Source::Buffer.new('(method)')
  buffer.source = method_source
  root = Docscribe::Parsing.parse_buffer(buffer)
  return FALLBACK_TYPE unless root && %i[def defs].include?(root.type)

  body = root.children.last
  last_expr_type(body, fallback_type: FALLBACK_TYPE, nil_as_optional: true) || FALLBACK_TYPE
rescue Parser::SyntaxError
  FALLBACK_TYPE
end

.infer_return_type_from_node(node) ⇒ String

Note:

module_function: when included, also defines #infer_return_type_from_node (instance visibility: private)

Infer a method’s normal return type from an already parsed def/defs node.

Parameters:

  • node (Parser::AST::Node) —

    ‘:def` or `:defs` node

Returns:

  • (String) 


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# File 'lib/docscribe/infer/returns.rb', line 37

def infer_return_type_from_node(node)
  body =
    case node.type
    when :def then node.children[2]
    when :defs then node.children[3]
    end

  return FALLBACK_TYPE unless body

  last_expr_type(body, fallback_type: FALLBACK_TYPE, nil_as_optional: true) || FALLBACK_TYPE
end

.last_expr_type(node, fallback_type:, nil_as_optional:, core_rbs_provider: nil, param_types: nil) ⇒ String?

Note:

module_function: when included, also defines #last_expr_type (instance visibility: private)

Infer the type of the last expression in a node.

Supports:

  • ‘begin` groups

  • ‘if` branches

  • ‘case` expressions

  • explicit ‘return`

  • literal-like expressions via Literals.type_from_literal

  • method calls with RBS core type lookup

Parameters:

  • node (Parser::AST::Node, nil) —

    expression node

  • fallback_type (String) —

    type used when inference is uncertain

  • nil_as_optional (Boolean) —

    whether ‘nil` unions should be rendered as optional types

  • core_rbs_provider (Object, nil) (defaults to: nil) —

    optional RBS provider for core type lookup

  • param_types (Hash, nil) (defaults to: nil) —

    parameter name -> type map for lvar resolution

Returns:

  • (String, nil) 


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# File 'lib/docscribe/infer/returns.rb', line 116

def last_expr_type(node, fallback_type:, nil_as_optional:, core_rbs_provider: nil, param_types: nil)
  return nil unless node

  case node.type
  when :begin
    last_expr_type(node.children.last, fallback_type: fallback_type, nil_as_optional: nil_as_optional,
                                       core_rbs_provider: core_rbs_provider, param_types: param_types)

  when :if
    t = last_expr_type(node.children[1], fallback_type: fallback_type, nil_as_optional: nil_as_optional,
                                         core_rbs_provider: core_rbs_provider, param_types: param_types)
    e = last_expr_type(node.children[2], fallback_type: fallback_type, nil_as_optional: nil_as_optional,
                                         core_rbs_provider: core_rbs_provider, param_types: param_types)
    unify_types(t, e, fallback_type: fallback_type, nil_as_optional: nil_as_optional)

  when :case
    branches = node.children[1..].compact.flat_map do |child|
      if child.type == :when
        last_expr_type(child.children.last, fallback_type: fallback_type, nil_as_optional: nil_as_optional,
                                            core_rbs_provider: core_rbs_provider, param_types: param_types)
      else
        last_expr_type(child, fallback_type: fallback_type, nil_as_optional: nil_as_optional,
                              core_rbs_provider: core_rbs_provider, param_types: param_types)
      end
    end.compact

    if branches.empty?
      fallback_type
    else
      branches.reduce do |a, b|
        unify_types(a, b, fallback_type: fallback_type, nil_as_optional: nil_as_optional)
      end
    end

  when :return
    Literals.type_from_literal(node.children.first, fallback_type: fallback_type)

  when :send
    recv = node.children[0]
    meth = node.children[1]

    # Try to resolve return type from RBS core for method calls
    if core_rbs_provider && recv&.type == :send
      # Chained call: arg.to_i.positive?
      inner_type = last_expr_type(recv, fallback_type: nil, nil_as_optional: false,
                                        core_rbs_provider: core_rbs_provider, param_types: param_types)
      if inner_type
        rbs_type = resolve_rbs_return_type(inner_type, meth, core_rbs_provider)
        return rbs_type unless rbs_type == FALLBACK_TYPE
      end
    elsif core_rbs_provider && recv&.type == :lvar
      # Direct call: arg.positive?
      lvar_name = recv.children.first
      if lvar_name && param_types
        recv_type = param_types[lvar_name.to_s]
        if recv_type
          rbs_type = resolve_rbs_return_type(recv_type, meth, core_rbs_provider)
          return rbs_type unless rbs_type == FALLBACK_TYPE
        end
      end
    end

    Literals.type_from_literal(node, fallback_type: fallback_type)

  else
    Literals.type_from_literal(node, fallback_type: fallback_type)
  end
end

.resolve_rbs_return_type(container_type, method_name, core_rbs_provider) ⇒ String

Note:

module_function: when included, also defines #resolve_rbs_return_type (instance visibility: private)

Resolve a return type from core RBS for a method call.

Parameters:

  • container_type (String) —

    e.g. “Numeric”, “String”

  • method_name (Symbol) —

    e.g. :positive?

  • core_rbs_provider (Object, nil) —

    RBS provider

Returns:

  • (String) —

    FALLBACK_TYPE if lookup fails



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# File 'lib/docscribe/infer/returns.rb', line 193

def resolve_rbs_return_type(container_type, method_name, core_rbs_provider)
  return FALLBACK_TYPE unless core_rbs_provider

  sig = core_rbs_provider.signature_for(
    container: container_type,
    scope: :instance,
    name: method_name
  )

  sig&.return_type || FALLBACK_TYPE
end

.returns_spec_from_node(node, fallback_type: FALLBACK_TYPE, nil_as_optional: true, core_rbs_provider: nil, param_types: nil) ⇒ Hash

Note:

module_function: when included, also defines #returns_spec_from_node (instance visibility: private)

Return a structured return-type spec for a method node.

The result includes:

  • ‘:normal` => normal/happy-path return type

  • ‘:rescues` => array of `[exception_names, return_type]` pairs for rescue branches

Parameters:

  • node (Parser::AST::Node) —

    ‘:def` or `:defs` node

  • fallback_type (String) (defaults to: FALLBACK_TYPE) —

    type used when inference is uncertain

  • nil_as_optional (Boolean) (defaults to: true) —

    whether ‘nil` unions should be rendered as optional types

  • core_rbs_provider (nil) (defaults to: nil) —

    Param documentation.

  • param_types (nil) (defaults to: nil) —

    Param documentation.

Returns:

  • (Hash) 


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# File 'lib/docscribe/infer/returns.rb', line 62

def returns_spec_from_node(node, fallback_type: FALLBACK_TYPE, nil_as_optional: true, core_rbs_provider: nil,
                           param_types: nil)
  body =
    case node.type
    when :def then node.children[2]
    when :defs then node.children[3]
    end

  spec = { normal: FALLBACK_TYPE, rescues: [] }
  return spec unless body

  if body.type == :rescue
    main_body = body.children[0]
    spec[:normal] =
      last_expr_type(main_body, fallback_type: fallback_type, nil_as_optional: nil_as_optional,
                                core_rbs_provider: core_rbs_provider, param_types: param_types) || FALLBACK_TYPE

    body.children.each do |ch|
      next unless ch.is_a?(Parser::AST::Node) && ch.type == :resbody

      exc_list, _asgn, rescue_body = *ch
      exc_names = Raises.exception_names_from_rescue_list(exc_list)
      rtype =
        last_expr_type(rescue_body, fallback_type: fallback_type, nil_as_optional: nil_as_optional,
                                    core_rbs_provider: core_rbs_provider, param_types: param_types) ||
        fallback_type
      spec[:rescues] << [exc_names, rtype]
    end
  else
    spec[:normal] =
      last_expr_type(body, fallback_type: fallback_type, nil_as_optional: nil_as_optional,
                           core_rbs_provider: core_rbs_provider, param_types: param_types) || FALLBACK_TYPE
  end

  spec
end

.unify_types(a, b, fallback_type:, nil_as_optional:) ⇒ String?

Note:

module_function: when included, also defines #unify_types (instance visibility: private)

Unify two inferred types into a single type string.

Rules:

  • identical types remain unchanged

  • ‘nil` unions may become optional types if enabled

  • otherwise falls back conservatively to ‘fallback_type`

Parameters:

  • a (String, nil)
  • b (String, nil)
  • fallback_type (String)
  • nil_as_optional (Boolean)

Returns:

  • (String, nil) 


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# File 'lib/docscribe/infer/returns.rb', line 218

def unify_types(a, b, fallback_type:, nil_as_optional:)
  a ||= fallback_type
  b ||= fallback_type
  return a if a == b

  if a == 'nil' || b == 'nil'
    non_nil = (a == 'nil' ? b : a)
    return nil_as_optional ? "#{non_nil}?" : "#{non_nil}, nil"
  end

  fallback_type
end