eject-enum

Eject enums from your TypeScript codebase.

What is this?

eject-enum is a code rewriting tool for TypeScript codebases that rewrites each TypeScript enum in your codebase to the safer alternative.

Before rewriting:

/**
 * Signals of traffic light.
 */
export enum TrafficLight {
    /** Stop. */
    Red,
    /** Stop unless you can't do so safely. */
    Yellow,
    /** Go. */
    Green,
}

After rewriting:

/**
 * Signals of traffic light.
 */
export const TrafficLight = {
    /** Stop. */
    Red: 0,
    /** Stop unless you can't do so safely. */
    Yellow: 1,
    /** Go. */
    Green: 2,
} as const;

export type TrafficLight = (typeof TrafficLight)[keyof typeof TrafficLight];

Usage

[!Note]

It is recommended to run code formatting tools after rewriting by eject-enum, as it doesn't consider any code formatting configurations of your project when rewriting.

As a CLI

You can execute eject-enum as a CLI tool:

# npm
npx eject-enum [options...]

# pnpm
pnpx eject-enum [options...]

# Bun
bunx eject-enum [options...]

# Deno >=2.6 (cf. https://deno.com/blog/v2.6#run-package-binaries-with-dx)
dx eject-enum [options...]

CLI Options:

# If no targets are specified, it tries to use `tsconfig.json` 
# in the current directory as the default target.
npx eject-enum

# Rewrite all files in projects specified by tsconfigs.
npx eject-enum path/to/tsconfig.json path/to/tsconfig2.json

# Rewrite all Typescript files under the `src` and `test` directories,
# except files under the `src/foo` directory.
npx eject-enum "src/**/*.ts" "test/**/*.ts" --exclude "src/foo/**/*.ts"

As a Library

You can use eject-enum as a library from your scripts as well.

npm install --save-dev eject-enum

import { ejectEnum, EjectEnumTarget } from "eject-enum";

// Rewrite all files in projects specified by paths to tsconfigs.
ejectEnum(
    EjectEnumTarget.projects([
        "path/to/tsconfig.json",
        "path/to/tsconfig2.json",
    ]),
);

// Rewrite all Typescript files under the `src` and `test` directories
// except files under the `src/foo` directory.
ejectEnum(
    EjectEnumTarget.srcPaths({
        include: ["src/**/*.ts", "test/**/*.ts"],
        exclude: ["src/foo/**/*.ts"],
    }),
);

Features

• [x] Rewrite enums in the top-level as well as nested in functions, namespaces and body of control flows (if, while, switch).
• [x] Rewrite enums that have constant enum expressions as member's value.
• [x] Preserve comments as much as possible.
• [x] Preserve original expressions of enum members in the original code as comments.
• [x] Rewrite an enum member used as a type.

Limitations

eject-enum have some limitations about code rewriting. They originate from limitations of the TS Compiler API/ts-morph.

• Can't rewrite enums that have computed enum members.
  • e.g. referring variables, members of other enums (even constant members)
• Can't preserve original trailing comments of enum members.