Our apps and packages are in a Turborepo monorepo that we deploy on Vercel. Most of our packages have a constants file that use some environment variables in order to do things like make requests to the right endpoints if in dev versus prod. We wrote a little script that takes the constants exported from that file and checks to make sure they all have values on them. Is there a way to run that script during a prebuild or postbuild of our applications that use them and if an environment variable is not set, have it cause the app build to fail? I've tried it on prebuild but it is failing even though the environment variables are set. I'm assuming it's because Vercel injects the environment variables after building or something along those lines.
159d ago
You're right about the timing of environment variables in Vercel deployments. There are a few important things to understand about how environment variables work in Turborepo monorepos on Vercel:
Environment Variables in Turborepo on Vercel
- Environment Variable Timing: Vercel does make environment variables available during the build process, but there are some nuances with how Turborepo handles them 12.
- Turborepo and
.envFiles: Turborepo itself doesn't load.envfiles into your task's runtime. This is left to your framework or tools likedotenv1. However, Turborepo needs to know about these variables for proper hashing. - Platform Environment Variables: Vercel automatically checks your configured environment variables against your
turbo.jsonconfiguration 1.
Solutions for Your Issue
Here are a few approaches to solve your problem:
1. Use the --env-mode=looseFlag
If you're having issues with environment variables not being found during builds, you can use Loose Mode:
turbo run build --env-mode=looseThis makes it easier to get started, but be aware that it doesn't filter environment variables according to your globalEnv and env keys 1.
2. Properly Configure turbo.json
Make sure your turbo.json properly declares all environment variables:
{
"pipeline": {
"build": {
"dependsOn": ["^build"],
"env": [
"API_URL",
"OTHER_ENV_VAR"
// List all env vars used in builds
]
}
},
"globalEnv": [
// Env vars that affect all tasks
"NODE_ENV"
]
}3. Move Your Validation to a Better Hook Point
Instead of using prebuild, consider:
- Using a custom build script that runs your validation before calling the actual build command
- Using the Ignored Build Step feature on Vercel to run your validation 3
Here's an example of a custom build script in your package.json:
{
"scripts": {
"build": "node validate-env.js && next build",
"validate-env": "node validate-env.js"
}
}4. Use eslint-config-turbo
Turborepo provides an ESLint config that helps you find environment variables used in your code that aren't listed in your turbo.json 1. This can help ensure all your environment variables are properly accounted for.
Best Practices
- Place
.envfiles in packages rather than at the root of the repository 1 - Avoid creating or mutating environment variables at runtime as Turborepo hashes them at the beginning of the task 1
- Use
--summarizeflag to identify any missing environment variables in your configuration 1
By implementing these changes, you should be able to properly validate your environment variables during the build process.
159d ago