ConfigService advantages over dotenv

Question

Is there any advantages (or disadvantages) on using @NestJS/Config instead of using dotenv to retrieve envvar? In both cases I could create a class that is responsible for all envvars, but should I?

I know @NestJS/Config uses dotenv behind the curtains, but is there any reason why one should choose one over the other?

Answer 1

My understanding is using @nestjs/config is easy for you to manage your config/envvars as a module in your project. So it can be easily swapped in different place:

eg if you need a different set of config for test, you don't have to actually modify your process.env.xxx or use a different.env file.

However if you do that, it requires all/most your other services to utilize this pattern as well. It wouldn't be so helpful if you have all your other service to be a pure function export.

Answer 2

The two big advantages are the ability to use Joi or class-validator or whatever else you want as a schema validator to ensure you have your env values correct to begin with, before trying to access them at runtime and getting an error. Earlier feedback loop means fewer failures later on. The other big advantage is the use of DI meaning it's easier (usually) to mock the env variable value in your test cases, rather than having to assign to process.env itself. There's also slight speed improvements, as Nest caches the value so if you read it again you don't need to read from process.env , but other than that there's not too much to mention. If you don't want to use it, don't feel like you have to. There is also the disadvantage of not being able to use the ConfigService inside a decorator