Envow

A vow-driven env validation library.

Installation

Install this package as a dependency in the project:

# npm
npm i envow

# Yarn
yarn add envow

# pnpm
pnpm add envow

# Deno
deno add npm:envow

# Bun
bun add envow

Usage

createEnv validates the runtime environment against a Standard Schema dictionary and returns a read-only, typed object.

import { createEnv } from "envow";
import { z } from "zod";

const env = createEnv({
    target: "server",
    runtimeEnv: process.env,
    define: {
        MODE: z.enum(["development", "production"]),
        PORT: z.number(),
    },
});

env.PORT; // number

zod is the user's own dependency (pnpm add zod). envow accepts any Standard Schema v1 validator (zod, valibot, arktype, ...).

Extending env

createExtension builds a extension that can be composed into a createEnv call via the extends option. The parent call resolves runtimeEnv once and validates all keys (its own plus each extension's) in a single pass — extension code never touches the runtime environment.

import { createEnv, createExtension } from "envow";
import { z } from "zod";

const base = createExtension({
    define: {
        NODE_ENV: z.enum([
            "development",
            "test",
            "production",
        ]),
        LOG_LEVEL: z.enum([
            "debug",
            "info",
            "warn",
            "error",
        ]).default("info"),
    },
});

const env = createEnv({
    target: "server",
    runtimeEnv: process.env,
    extends: [
        base,
    ],
    define: {
        PORT: z.number(),
    },
});

env.NODE_ENV;  // "development" | "test" | "production"
env.LOG_LEVEL; // "debug" | "info" | "warn" | "error"
env.PORT;      // number

Extension define dictionaries are merged in array order; the user's define wins on key collision.

Contributing

For contributing, please refer to the contributing guide.

Credits

This project is inspired by t3-env with the following differences:

• Extensions are schema-only; runtimeEnv is resolved alongside createEnv, not inside a extension.

• More composable while nestable extensions being merged in a single validation pass.

• Flat define + target/conditions instead of server/client/clientPrefix.

License

This project is licensed under the terms of the MIT license.