byethrow
  • English

      • no-throw-in-callback

      Disallows throw statements inside callbacks passed to @praha/byethrow functions such as Result.andThen, Result.map, etc.

      Rule details

      Throwing inside a @praha/byethrow callback breaks the Result contract, not an exception. Use Result.fail() to represent errors instead, keeping error handling explicit and composable.

      Incorrect

      import { 
      import Result
      Result       } from '@praha/byethrow';      

// ❌ throwing inside a callback
const 
      const result: Result.Result<number, never>
      result       = 
      import Result
      Result      .
      const pipe: <Result.Result<32, never>, Result.Result<number, never>>(a: Result.Result<32, never>, ab: (a: Result.Result<32, never>) => Result.Result<number, never>) => Result.Result<number, never> (+25 overloads)
      pipe      (      
  
      import Result
      Result      .
      const succeed: <32>(value: 32) => Result.Result<32, never> (+1 overload)
      succeed      (32),      
  
      import Result
      Result      .
      const andThen: <Result.Result<32, never>, Result.Result<number, never>>(fn: (a: 32) => Result.Result<number, never>) => (result: Result.Result<32, never>) => Result.Result<number, never> (+1 overload)
      andThen      ((
      value: 32
      value      ) => {      
    if (
      value: 32
      value       < 0) throw new 
      var RangeError: RangeErrorConstructor
new (message?: string, options?: ErrorOptions) => RangeError (+3 overloads)
      RangeError      ('negative value');      
    return 
      import Result
      Result      .
      const succeed: <number>(value: number) => Result.Result<number, never> (+1 overload)
      succeed      (
      value: 32
      value       * 2);      
  }),
);

      Correct

      import { 
      import Result
      Result       } from '@praha/byethrow';      

// ✅ returning a failure Result
const 
      const result: Result.Result<number, NegativeValueError>
      result       = 
      import Result
      Result      .
      const pipe: <Result.Result<32, never>, Result.Result<number, NegativeValueError>>(a: Result.Result<32, never>, ab: (a: Result.Result<32, never>) => Result.Result<number, NegativeValueError>) => Result.Result<number, NegativeValueError> (+25 overloads)
      pipe      (      
  
      import Result
      Result      .
      const succeed: <32>(value: 32) => Result.Result<32, never> (+1 overload)
      succeed      (32),      
  
      import Result
      Result      .
      const andThen: <Result.Result<32, never>, Result.Failure<NegativeValueError> | Result.Success<number>>(fn: (a: 32) => Result.Failure<NegativeValueError> | Result.Success<number>) => (result: Result.Result<32, never>) => Result.Result<number, NegativeValueError> (+1 overload)
      andThen      ((
      value: 32
      value      ) => {      
    if (
      value: 32
      value       < 0) return 
      import Result
      Result      .
      const fail: <NegativeValueError>(error: NegativeValueError) => Result.Result<never, NegativeValueError> (+1 overload)
      fail      (new 
      constructor NegativeValueError(message?: string, options?: ErrorOptions): NegativeValueError (+1 overload)
      NegativeValueError      ());      
    return 
      import Result
      Result      .
      const succeed: <number>(value: number) => Result.Result<number, never> (+1 overload)
      succeed      (
      value: 32
      value       * 2);      
  }),
);