@julr/vite-plugin-validate-env

This Vite plugin allows you to validate your environment variables at build or dev time. This allows your build/dev-server to fail-fast if your setup is misconfigured.

No more CI to restart because you are missing an environment variable, or to realize after 10 minutes of debugging that you forgot a variable 🥲

Features

• Validate your environment variables at build time only. No runtime overhead
• Totally type-safe
• Support standard-schema, meaning you can use every libraries compatible with it ( Zod, Valibot, ArkType )
• Parsing, validation and transformation of your variables
• Custom rules and error messages

Installation

pnpm add -D @julr/vite-plugin-validate-env

Usage

vite-plugin-validate-env plugin allows you to validate your env, either with a very simplified builtin validation lib, or with Zod in the most complex cases when you want a very strict validation.

Plugin options

The easiest way to define the options is to directly define the scheme as follows:

// vite.config.ts
import { defineConfig } from "vite";
import { Schema, ValidateEnv } from "@julr/vite-plugin-validate-env";

export default defineConfig({
  plugins: [
    ValidateEnv({
      VITE_MY_VAR: Schema.string()
    }),
  ],
})

In case you want to change some plugin options, in particular change the validator (for Zod), you have to set your options as follows:

import { defineConfig } from "vite";
import { z } from 'zod'
import { ValidateEnv } from "@julr/vite-plugin-validate-env";

export default defineConfig({
  plugins: [
    ValidateEnv({
      validator: 'zod',
      schema: {
        VITE_MY_VAR: z.string()
      }
    }),
  ],
})

If you want to see what values are being evaluated for the build, for example when running in CI. You can pass the debug option as follows:

import { defineConfig } from "vite";
import { Schema, ValidateEnv } from "@julr/vite-plugin-validate-env";

export default defineConfig({
  plugins: [
    ValidateEnv({
      debug: true,
      schema: {
        VITE_MY_VAR: Schema.string()
      }
    }),
  ],
})

Built-in validator

import { Schema, ValidateEnv } from "@julr/vite-plugin-validate-env"
import { defineConfig } from "vite";

export default defineConfig({
  plugins: [
    ValidateEnv({
      // Data types
      VITE_STRING_VARIABLE: Schema.string(),
      VITE_BOOLEAN_VARIABLE: Schema.boolean(),
      VITE_NUMBER_VARIABLE: Schema.number(),
      VITE_ENUM_VARIABLE: Schema.enum(['foo', 'bar'] as const),
      
      // Optional variable
      VITE_OPTIONAL_VARIABLE: Schema.boolean.optional(),

      // Specify string format
      VITE_AUTH_API_URL: Schema.string({ format: 'url', protocol: true }),

      // Specify error message
      VITE_APP_PORT: Schema.number({ message: 'You must set a port !' }),

      // Custom validator
      VITE_CUSTOM_VARIABLE: (key, value) => {
        if (!value) {
          throw new Error(`Missing ${key} env variable`)
        }

        if (value.endsWith('foo')) {
          throw new Error('Value cannot end with "foo"')
        }

        return value
      },
    }),
  ],
})

Zod Validator

To use the Zod validator, you must first install it if you have not already done so

pnpm install zod

Then, you can use it as follows:

// env.ts
import { defineConfig } from '@julr/vite-plugin-validate-env'
import { z } from 'zod'

export default defineConfig({
  validator: 'zod',
  schema: {
    VITE_MY_STRING: z.string().min(5, 'This is too short !'),
    VITE_ENUM: z.enum(['a', 'b', 'c']),
    VITE_BOOLEAN_VARIABLE: z.boolean(),
  }
})

Beware, there are some limitations if you use Zod. For example, you can't use a boolean or number type directly. Because everything that comes from your .env file is a string by default.

So to validate other types than string you must use preprocess, and transform, like this:

// env.ts
import { defineConfig } from '@julr/vite-plugin-validate-env'
import { z } from 'zod'

export default defineConfig({
  validator: 'zod',
  schema: {
    // This will transform the string 'true' or '1' to a boolean
    VITE_BOOLEAN_VARIABLE: z
      .preprocess((value) => value === 'true' || value === '1', z.boolean()),

    // Will convert the string to a number
    VITE_NUMBER: z.preprocess((value) => Number(value), z.number()),

    // Will parse the string to an object
    VITE_OBJECT: z.preprocess(
      (value) => JSON.parse(value as string),
      z.object({
        a: z.string(),
        b: z.number(),
      }),
    ),
  }
})

In this case, true and 1 will be transformed to true and your variable will be valid and considered as a boolean.

Dedicated config file

You can also add a env.ts file at the root of your project to define your environment variables.

// vite.config.ts
import { defineConfig } from 'vite'
import { ValidateEnv } from "@julr/vite-plugin-validate-env";

export default defineConfig({
  plugins: [ValidateEnv()],
})

// env.ts
import { defineConfig, Schema } from '@julr/vite-plugin-validate-env'

export default defineConfig({
 VITE_MY_VAR: Schema.enum(['foo', 'bar'] as const),
})

Custom config file path

By default, the plugin is looking for a file named env.ts at the root of your project. If you want to use a different file, you can specify the path to your file in the plugin options.

// vite.config.ts
import { defineConfig } from 'vite'
import { ValidateEnv } from "@julr/vite-plugin-validate-env";

export default defineConfig({
  plugins: [ValidateEnv({ configFile: 'config/env' })],
})

This will look for a file named env.ts in the config folder at the root of your project. Make sure to not include the file extension in the path as the plugin will automatically search for .js, .ts and other valid file extensions.

Transforming variables

In addition to the validation of your variables, there is also a parsing that is done. This means that you can modify the value of an environment variable before it is injected.

Let's imagine the following case: you want to expose a variable VITE_AUTH_API_URL in order to use it to call an API. However, you absolutely need a trailing slash at the end of this environment variable. Here's how it can be done :

// Built-in validation
import { defineConfig, Schema } from '@julr/vite-plugin-validate-env'

export default defineConfig({
  VITE_AUTH_API_URL: (key, value) => {
    if (!value) {
      throw new Error(`Missing ${key} env variable`)
    }

    if (!value.endsWith('/')) {
      return `${value}/`
    }

    return value
  },
})

// Zod validation
import { defineConfig } from '@julr/vite-plugin-validate-env'
import { z } from 'zod'

export default defineConfig({
  validator: 'zod',
  schema: {
    VITE_AUTH_API_URL: z
      .string()
      .transform((value) => value.endsWith('/') ? value : `${value}/`),
  },
})

Now, in your client front-end code, when you call import.meta.env.VITE_AUTH_API_URL, you can be sure that it will always end with a slash.

Typing import.meta.env

In order to have a type-safe import.meta.env, the ideal is to use the dedicated configuration file env.ts. Once this is done, you would only need to add an env.d.ts in src/ folder to augment ImportMetaEnv (as suggested here ) with the following content:

/// <reference types="vite/client" />

type ImportMetaEnvAugmented = import('@julr/vite-plugin-validate-env').ImportMetaEnvAugmented<
  typeof import('../env').default
>

interface ImportMetaEnv extends ImportMetaEnvAugmented {
  // Now import.meta.env is totally type-safe and based on your `env.ts` schema definition
  // You can also add custom variables that are not defined in your schema
}

Standard Schema

[!WARNING]
As long as standard-schema has not been published in 1.0.0, I will possibly make breaking changes to the API without major release.

standard-schema is basically an attempt to standardize the way we can use validation librairies. It means that you can use any library that is compatible with it. As the date of writing, Zod, Valibot, Arktype, ArriSchema are compatible.

Here is an example of how to use it with the plugin:

// Zod validation
import { defineConfig } from '@julr/vite-plugin-validate-env'
import { z } from 'zod'
import * as v from 'valibot'
import { type } from 'arktype'

export default defineConfig({
  validator: 'standard', // Make sure to use 'standard' validator
  schema: {
    // Zod
    VITE_ZOD_VARIABLE: z.string(),

    // Valibot
    VITE_VALIBOT_VARIABLE: v.string(),

    // Arktype
    VITE_ARKTYPE_VARIABLE: type.string(),
  },
})

Make sure to upgrade your validation library to the latest version to ensure using a compatible version with standard-schema. For example, Zod minimum version is 3.24.0.

Forbid unknown variables

Since we rely on module augmentation to type import.meta.env, using unknown variables won’t trigger errors because the ImportMetaEnv interface from Vite includes a [key: string]: string signature.

To enforce stricter typing and prevent the use of unknown variables, you can set up the following:

// lib/env.ts or wherever you want
import { ImportMetaEnvAugmented } from '@julr/vite-plugin-validate-env';

export const env: ImportMetaEnvAugmented = import.meta.env;

By using env instead of import.meta.env in your code, TypeScript will now throw an error if you try to access an unknown variable.

Sponsors

If you like this project, please consider supporting it by sponsoring it. It will help a lot to maintain and improve it. Thanks a lot !

License

MIT License © 2022 Julien Ripouteau