ResulTS

This package provides robust implementations of the Result and Option types, inspired by functional programming principles, to handle success/failure scenarios and optional values in your TypeScript backend applications. It also includes helper functions and a match function for convenient usage.

The Result<T, E> type is heavily inspired by Rust's Result and aims to provide a robust way to handle success and failure scenarios in TypeScript.

The Option<T> type is heavily inspired by Rust's Option and aims to provide a robust way to handle optional values in TypeScript, avoiding null and undefined issues.

Installation (Global Availability Recommended)

For ease of use, the Ok, Err, Some, None, and match functions can be made globally available in your TypeScript project.

1. Configure tsconfig.json:

   Within the compilerOptions, add the following to the types array:

   "types": ["vitest/globals", "@consolidados/results/globals"]

2. Import in Entry Point (e.g., main.ts or index.ts):

   Import the entire package in your main application file:

   // main.ts
   import "@consolidados/results";

   After this setup, you can use Ok, Err, Some, None, and match directly in your code without explicit imports.

Core Concepts

Result<T, E>

The Result<T, E> type represents the outcome of an operation that can either succeed with a value of type T or fail with an error of type E (typically extending Error).

Generic Types:

• T: The type of the successful value.
• E: The type of the error value (should extend Error).

Usage Example:

function divide(a: number, b: number): Result<number, Error> {
  if (b === 0) {
    return Err(new Error("Cannot divide by zero"));
  }
  return Ok(a / b);
}

const result1 = divide(10, 2);
const result2 = divide(10, 0);

if (result1.isOk()) {
  console.log("Result:", result1.unwrap()); // Output: Result: 5
}

if (result2.isErr()) {
  console.error("Error:", result2.unwrapErr().message); // Output: Error: Cannot divide by zero
}

Ok<T>

Represents a successful result containing a value of type T.

Constructor:

new Ok<T>(value: T)

Example:

const successResult: Result<string, Error> = Ok("Operation successful");

Err<E extends Error>

Represents a failed result containing an error of type E.

Constructor:

new Err<E>(error: E | string)

Example:

const failureResult: Result<number, Error> = Err(new Error("Operation failed"));
const failureResultWithMessage: Result<number, Error> = Err("Something went wrong");

Result Methods

• isOk(): this is Ok<T>: Checks if the result is a successful Ok value.
• isErr(): this is Err<E>: Checks if the result is a failed Err value.
• unwrap(): T: Extracts the successful value or throws an error if it's an Err.
• unwrapErr(): E: Extracts the error value or throws an error if it's an Ok.
• map<U>(fn: (value: T) => U): Result<U, E>: Applies a transformation function to the value of an Ok.
• flatMap<U>(fn: (value: T) => Result<U, E>): Result<U, E>: Applies a function that returns a Result to the value of an Ok.
• mapErr<U extends Error>(fn: (err: E) => U): Result<T, U>: Applies a transformation function to the error value of an Err.

Option<T>

The Option<T> type represents an optional value that may or may not exist.

Generic Type:

• T: The type of the optional value.

Usage Example:

function findUser(id: number): Option<string> {
  if (id === 123) {
    return Some("John Doe");
  }
  return None();
}

const user1 = findUser(123);
const user2 = findUser(456);

if (user1.isSome()) {
  console.log("User:", user1.unwrap()); // Output: User: John Doe
}

if (user2.isNone()) {
  console.log("User not found"); // Output: User not found
}```

#### `Some<T>`

Represents an `Option` that contains a value of type `T`.

**Constructor:**

```TypeScript

new Some<T>(value: T)

Example:

const presentValue: Option<number> = Some(42);

None

Represents an Option that does not contain a value.

Example:

const absentValue: Option<string> = None();

Option Methods

• isSome(): this is Some<T>: Checks if the option contains a value (Some).
• isNone(): this is None: Checks if the option does not contain a value (None).
• unwrap(): T: Extracts the value from a Some or throws an error if it's None.
• map<U>(fn: (value: T) => U): Option<U>: Applies a transformation function to the value of a Some.
• flatMap<U>(fn: (value: T) => Option<U>): Option<U>: Applies a function that returns an Option to the value of a Some.
• unwrapOr(defaultValue: T): T: Extracts the value from a Some or returns a default value if it's None.

match Function

The match function provides a concise way to handle different cases for both Result and Option types.

Usage with Result:

const result: Result<string, Error> = Ok("Success");

const optionResult: Option<string> = match(result, {
  Ok: (value) => Some(value),
  Err: (error) => None(),
});

match(result, {
  Ok: (value) => console.log("Success Value: " + value),
  Err: (err) => console.log("Err Value: " + err),
});

Usage with Option:

`const someValue: Option<number> = Some(10);

match(someValue, {
  Some: (value) => console.log("Option has value: " + value),
  None: () => console.log("Option is None"),
});

match(someValue, {
  Some: (value) => Ok(value),
  None: () => Err("Option is None"),
});

API Reference

Result<T, E>

Methods

• isOk(): this is Ok<T>
  • Checks if the result is an Ok instance.
  • Returns: true if it's an Ok, false otherwise.
• isErr(): this is Err<E>
  • Checks if the result is an Err instance.
  • Returns: true if it's an Err, false otherwise.
• unwrap(): T
  • Retrieves the value contained in an Ok instance.
  • Throws an Error if called on an Err instance.
• unwrapErr(): E
  • Retrieves the error contained in an Err instance.
  • Throws an Error if called on an Ok instance.
• map<U>(fn: (value: T) => U): Result<U, E>
  • Applies a function fn to the value of an Ok instance and returns a new Result with the transformed value.
  • If the Result is an Err, it returns the original Err without applying the function.
  • Parameters:
    • fn: (value: T) => U: The function to apply to the value.
  • Returns: A new Result with the transformed value or the original Err.
• flatMap<U>(fn: (value: T) => Result<U, E>): Result<U, E>
  • Applies a function fn that returns a Result to the value of an Ok instance.
  • If the Result is an Err, it returns the original Err.
  • Parameters:
    • fn: (value: T) => Result<U, E>: The function to apply to the value.
  • Returns: The result of applying the function or the original Err.
• mapErr<U extends Error>(fn: (err: E) => U): Result<T, U>
  • Applies a function fn to the error of an Err instance and returns a new Result with the transformed error.
  • If the Result is an Ok, it returns the original Ok without applying the function.
  • Parameters:
    • fn: (err: E) => U: The function to apply to the error.
  • Returns: A new Result with the transformed error or the original Ok.

Option<T>

Methods

• isSome(): this is Some<T>
  • Checks if the option is a Some instance.
  • Returns: true if it's a Some, false otherwise.
• isNone(): this is None
  • Checks if the option is a None instance.
  • Returns: true if it's a None, false otherwise.
• unwrap(): T
  • Retrieves the value contained in a Some instance.
  • Throws an Error if called on a None instance.
• map<U>(fn: (value: T) => U): Option<U>
  • Applies a function fn to the value of a Some instance and returns a new Option with the transformed value.
  • If the Option is None, it returns None.
  • Parameters:
    • fn: (value: T) => U: The function to apply to the value.
  • Returns: A new Option with the transformed value or None.
• flatMap<U>(fn: (value: T) => Option<U>): Option<U>
  • Applies a function fn that returns an Option to the value of a Some instance.
  • If the Option is None, it returns None.
  • Parameters:
    • fn: (value: T) => Option<U>: The function to apply to the value.
  • Returns: The result of applying the function or None.
• unwrapOr(defaultValue: T): T
  • Retrieves the value contained in a Some instance.
  • If the Option is None, it returns the provided defaultValue.
  • Parameters:
    • defaultValue: T: The value to return if the Option is None.
  • Returns: The value of the Some instance or the defaultValue.

match Function

• Provides pattern matching for Result and Option types.
• Requires handlers for all possible cases (Ok, Err for Result; Some, None for Option).

Work in Progress (WIP)

Result

Current Implementation

The Result type currently implements the following methods:

• [x] isOk(): Checks if the result is Ok.
• [x] isErr(): Checks if the result is Err.
• [x] unwrap(): Extracts the successful value or throws an error.
• [x] unwrapErr(): Extracts the error value.
• [x] map(fn): Maps a successful value using a function.
• [x] flatMap(fn): Applies a function that returns a Result.
• [x] mapErr(fn): Maps an error value using a function.
• [x] ok(): Converts Result<T, E> into Option<T>.

Methods to be Developed

The following methods are planned for future development:

• [ ] ok(): Converts Result<T, E> into Option<T>.
• [ ] err(): Converts Result<T, E> into Option<E>.
• [ ] and(res): Returns Err if self is Err, otherwise returns res.
• [ ] andThen(fn): Calls fn if the result is Ok, otherwise returns Err.
• [ ] or(res): Returns Ok if self is Ok, otherwise returns res.
• [ ] orElse(fn): Calls fn if the result is Err, otherwise returns Ok.
• [ ] unwrapOr(defaultValue): Extracts the successful value or returns a default value.
• [ ] unwrapOrElse(fn): Extracts the successful value or calls a function to get a default value.
• [ ] transpose(): Transposes a Result<Option<T>, E> into an Option<Result<T, E>>.
• [ ] flatten(): Flattens a nested Result<Result<T, E>, E> into a Result<T, E>.

Option

Current Implementation

The Option type currently implements the following methods:

• [x] isSome(): Checks if the option is Some.
• [x] isNone(): Checks if the option is None.
• [x] unwrap(): Extracts the value or throws an error if None.
• [x] map(fn): Maps a Some value using a function.
• [x] flatMap(fn): Applies a function that returns an Option.
• [x] unwrapOr(defaultValue): Extracts the value or returns a default value.

Methods to be Developed

The following methods are planned for future development:

• [ ] expect(message): Extracts the value or throws an error with a custom message if None.
• [ ] okOr(err): Converts Option<T> into Result<T, E>.
• [ ] okOrElse(errFn): Converts Option<T> into Result<T, E> using a function to create the error.
• [ ] and(optb): Returns None if self is None, otherwise returns optb.
• [ ] andThen(fn): Calls fn if the option is Some, otherwise returns None.
• [ ] or(optb): Returns self if Some, otherwise returns optb.
• [ ] orElse(fn): Returns self if Some, otherwise calls fn to get an Option.
• [ ] unwrapOrElse(fn): Extracts the value or calls a function to get a default value.
• [ ] filter(predicate): Returns Some if the value matches the predicate, otherwise None.
• [ ] zip(other): Zips two Option values into a tuple if both are Some.
• [ ] zipWith(other, fn): Zips two Option values using a function if both are Some.
• [ ] transpose(): Transposes an Option<Result<T, E>> into a Result<Option<T>, E>.

Contributing

Contributions to this package are welcome. Feel free to open issues and submit pull requests.