9 releases

0.2.6	Feb 16, 2021
0.2.4	Feb 3, 2021
0.1.10	Feb 2, 2021
0.1.2	Jan 29, 2021

#679 in Text processing

43 downloads per month

MIT/Apache

43KB
1K SLoC

`enum-ts`

Place this definition somewhere in your project:

/**
 * This special type can help generate pattern matchers for you!
 * Just use it as so:
 *
 *    type Result<Ok, Err> = Enum<{
 *      Ok: Ok,
 *      Err: Err,
 *    }>
 */
export type Enum<T extends { [Variant: string]: any }> = {
  [P in keyof T]: Record<P, T[P]>;
}[keyof T];

Now whenever you write a type with Enum definition at the root of a file (cannot be nested in another block), then enum-ts will be able to generate exhaustive pattern matchers and constructor code for you!

Install

This is currently just an executable you can install through compiling through cargo, or use by installing through npm.

cargo install enum-ts
# build from source hosted on crates.io


npm install --global enum-ts-bin
# install from npm registry with npm


yarn global add enum-ts-bin
# install from npm registry with yarn


enum-ts --version
# print version

Then, you can test it out with one of the examples in tests/ or in this README:

cat ./tests/result.ts | enum-ts

Which will print the generated enum matcher helpers!

CLI

enum-ts
# no arguments puts enum-ts into pipe-mode

cat my-file.ts | enum-ts
# prints what would be generated from this file (mostly for debugging purposes)

enum-ts --write .
# recursively walks down the directory looking for *.ts & *.tsx files
# to write updates to directly

enum-ts .
# "dry-run" will only print out what it would have rewritten the files to if given the `--write` flag.

Examples

Result

Input

type Result<O, E> = Enum<{
  Ok: O;
  Err: E;
}>;

Generated

export type Ok<O, E> = O;
export type Err<O, E> = E;
export function Ok<O, E>(contents: Ok<O, E>): { Ok: Ok<O, E> } {
  return { Ok: contents };
}
export function Err<O, E>(contents: Err<O, E>): { Err: Err<O, E> } {
  return { Err: contents };
}
export function isOk<O, E>(item: Result<O, E>): item is { Ok: Ok<O, E> } {
  return item != null && "Ok" in item;
}
export function isErr<O, E>(item: Result<O, E>): item is { Err: Err<O, E> } {
  return item != null && "Err" in item;
}
export namespace Result {
  const unexpected = "Unexpected Enum variant for Result<O, E>";
  export function apply<O, E, R>(fns: {
    Ok(content: Ok<O, E>): R;
    Err(content: Err<O, E>): R;
  }): (value: Result<O, E>) => R {
    return function matchResultApply(item) {
      return "Ok" in item
        ? fns.Ok(item.Ok)
        : "Err" in item
        ? fns.Err(item.Err)
        : (console.assert(false, unexpected, item) as never);
    };
  }
  export function match<O, E, R>(
    value: Result<O, E>,
    fns: {
      Ok(content: Ok<O, E>): R;
      Err(content: Err<O, E>): R;
    }
  ): R {
    return apply(fns)(value);
  }
}

Usage

const res = Ok<string, any>("okay value");
Result.match(res, {
  Ok(value) {
    // do something with value
  },
  Err(err) {
    // do something with err
  },
});
if (isOk(res)) {
  console.assert(res.Ok === "okay value");
}

`BinaryTree<T>`

Input

export type BinaryTree<T> = Enum<{
  Leaf: T;
  Branch: {
    left: BinaryTree<T>;
    right: BinaryTree<T>;
  };
}>;

Generated

export type Leaf<T> = T;
export type Branch<T> = {
  left: BinaryTree<T>;
  right: BinaryTree<T>;
};
export function Leaf<T>(contents: Leaf<T>): { Leaf: Leaf<T> } {
  return { Leaf: contents };
}
export function Branch<T>(contents: Branch<T>): { Branch: Branch<T> } {
  return { Branch: contents };
}
export function isLeaf<T>(item: BinaryTree<T>): item is { Leaf: Leaf<T> } {
  return item != null && "Leaf" in item;
}
export function isBranch<T>(item: BinaryTree<T>): item is { Branch: Branch<T> } {
  return item != null && "Branch" in item;
}
export namespace BinaryTree {
  const unexpected = "Unexpected Enum variant for BinaryTree<T>";
  export function apply<T, R>(fns: {
    Leaf(content: Leaf<T>): R;
    Branch(content: Branch<T>): R;
  }): (value: BinaryTree<T>) => R {
    return function matchBinaryTreeApply(item) {
      return "Leaf" in item
        ? fns.Leaf(item.Leaf)
        : "Branch" in item
        ? fns.Branch(item.Branch)
        : (console.assert(false, unexpected, item) as never);
    };
  }
  export function match<T, R>(
    value: BinaryTree<T>,
    fns: {
      Leaf(content: Leaf<T>): R;
      Branch(content: Branch<T>): R;
    }
  ): R {
    return apply(fns)(value);
  }
}

Development

cargo install --path ./enum-ts: Install locally after cloning repo

License

^{Licensed under either of Apache License, Version
2.0 or MIT license at your option.}
_{Unless you explicitly state otherwise, any contribution intentionally submitted
for inclusion in this crate by you, as defined in the Apache-2.0 license, shall
be dual licensed as above, without any additional terms or conditions.}

Dependencies

~4–6MB
~95K SLoC