rlse

rlse

Rlse (pronounced “release”) is an open-source library that makes feature flags a first-class citizen in your codebase. With Rlse, you can easily manage feature flag definitions directly in your code, improving consistency, simplicity, and efficiency in your release process.

Installation

Install the npm package

Add Rlse to your project using npm:

$ npm install rlse -S

Create a configuration file

Create a configuration file in the root of your project to define your feature flags. By default, Rlse looks for a file named rlse.toml. Here’s an example:

[features]
testFeature1 = { environments = ['dev', 'test']}
testFeature2 = { environments = ['test']}
testFeature3 = { environments = ['dev', 'uat', 'test', 'prod']}

If you prefer a different file name, set the RLSE_CONFIG environment variable to point to it. For example:

export RLSE_CONFIG=my_custom_config.toml

💡 Tip: Ensure the configuration file is included in your build process so it deploys with your application.

Defining Features

The [features] section is where you define your feature flags. Each feature is a key-value pair, where the key is the feature name and the value specifies the environments in which it is enabled.

Example:

[features]
uniqueFriendlyFeatureName = { environments = ['dev', 'test']}

In this example:

• The uniqueFriendlyFeatureName feature is enabled only in the dev environment.
• The environment can be determined dynamically from the APP_ENV or VERCEL_ENV environment variable or explicitly passed when testing the feature flag.

Usage

Rlse makes it easy to conditionally enable features based on your configuration. Use the is_enabled function to check whether a feature is active in a given environment.

Example:

import { isFeatureEnabled } from "rlse";

// Automatically uses environment variabls:
//   env: process.env.APP_ENV | rocess.env.VERCEL_ENV | 'dev'
//   config: process.env.RLSE_CONFIG | 'rlse.toml'.
if (isFeatureEnabled({ feature: "testFeatureDevTest" })) {
  // Feature-specific logic ...
}

// Explicitly specify the environment and/or config data.
// This is useful in a browser/client where bundling your toml file with your app is required.
if (isFeatureEnabled({ feature: "missingFeature", env: "dev", config })) {
  // Feature-specific logic ...
}

Next.js Example Next.js has some special ways of working. There's a little hackery required to get rlse working since it tends to loath node.js modules. (I'm sure there's better ways that someone smarter than me could do. I'm open to learning new things.) Put this in a server action or API route that can be reused throughout your app.

import { promises as fs } from "fs";
import { isFeatureEnabled, parseConfig, type Config } from "rlse";

let rlseConfig: Config;

export async function isEnabled(feature: string): Promise<boolean> {
  if (!rlseConfig) {
    rlseConfig = parseConfig(await fs.readFile("rlse.toml", "utf-8"));
  }

  return await isFeatureEnabled({
    feature,
    env: process.env.VERCEL_ENV,
    config: rlseConfig,
  });
}

Then you can call it like so from pages

import { isEnabled } from "./actions";

export default async function Page() {
  const featureEnabled = await isEnabled("myCustomFeature");
  ...
}

🛑 Important:

• is_enabled() will return false unless the feature/environment combination is explicitly defined in the configuration file.
• Ensure your configuration file accurately reflects your environment setup.

Why Choose Rlse?

• Simplify Feature Management: Centralize and standardize feature flag definitions across environments.
• First-Class Code Citizen: Keep feature flags in your codebase, reducing the risk of misalignment.