Linting with Syntax Tree

linter.rb

# frozen_string_literal: true

module SyntaxTree
  # This class is used to create a mutation that transforms syntax trees based
  # on various linting rules.
  class Linter
    def mutation
      SyntaxTree.mutation do |mutator|
        # Lint/AssignmentInCondition
        mutator.mutate("IfNode[predicate: Assign | OpAssign] | UnlessNode[predicate: Assign | OpAssign] | WhileNode[predicate: Assign | OpAssign] | UntilNode[predicate: Assign | OpAssign]") do |node|
          node.copy(predicate: Paren.new(
            lparen: LParen.default,
            contents: node.predicate,
            location: node.predicate.location
          ))
        end

        # Lint/BigDecimalNew
        mutator.mutate("CallNode[receiver: { value: { value: 'BigDecimal' } }, message: { value: 'new' }]") do |node|
          node.copy(receiver: nil, operator: nil, message: node.receiver)
        end

        # Lint/BinaryOperatorWithIdenticalOperands
        mutator.mutate("Binary[operator: :'&&']") do |node|
          node.left === node.right ? node.left : node
        end

        # Lint/BooleanSymbol
        mutator.mutate("SymbolLiteral[value: Kw[value: 'true' | 'false']]") do |node|
          node.value
        end

        # Lint/Debugger
        mutator.mutate("VCall[value: { value: 'debugger' }] | CallNode[receiver: { value: { value: 'binding' } }, message: { value: 'pry' | 'irb' }]") do |node|
          VoidStmt.new(location: node.location)
        end

        # Lint/LiteralInInterpolation
        mutator.mutate("StringEmbExpr[statements: { body: [FloatLiteral | Imaginary | Int | RationalLiteral | VarRef[value: { value: 'false' | 'true' | 'nil' }]] }]") do |node|
          case (literal = node.statements.body.first)
          when FloatLiteral, Imaginary, Int, RationalLiteral
            TStringContent.new(value: literal.value, location: node.location)
          when VarRef
            TStringContent.new(value: literal.value.value, location: node.location)
          end
        end
      end
    end
  end
end