What is the right environment variable and value to set when building for production?

[saikatdas0790]

For a SSR'd cargo-leptos project, the Cargo.toml has an entry that looks like this:

However, the deployment documentation in the book here:
https://leptos-rs.github.io/leptos/deployment.html

sets the APP_ENVIRONMENT variable to production

I am trying to confirm the exact enviroment variable and its corresponding value to set in my production builds. Is the value "PROD" or "production"? And is the variable name documented in the book accurate?

Thoughts on the right value to be used?

[gbj]

ENV is correct, the Dockerfile is just built on an older version and that is out of date. I'll remove it in the docs.

[saikatdas0790]

Just to confirm, the environment variable equivalent then becomes ENV or LEPTOS_ENV?

LEPTOS_ENV="PROD"

Or should this environment variable be removed completely and the binary has logic inside to detect what mode it needs to run in?

[saikatdas0790]

Any thoughts on this? What's the exact environment variable to be set in the Dockerfile?

[gbj]

Sorry, I misread your question above.

This is a case in which I need to look through the source code to find the answer, so I'm going to do that, and paste in what I find, so you can see how I did that.

Searching in the Leptos repo for LEPTOS_ENV brings me to leptos_config/src/lib.rs and to the default initialization of a field in the definition of a struct called LeptosOptions

leptos/leptos_config/src/lib.rs

Line 96 in 8573f22

env: env_from_str(env_w_default("LEPTOS_ENV", "DEV")?.as_str())?,

Ok, so the struct field is named env and the environment variable is LEPTOS_ENV.

I'm curious what the type of env is, so I scroll up and see that it's... Env

leptos/leptos_config/src/lib.rs

Line 47 in 8573f22

pub env: Env,

Conveniently GitHub links me to the enum definition of Env, which is either PROD or DEV

leptos/leptos_config/src/lib.rs

Lines 161 to 164 in 8573f22

	pub enum Env {
	PROD,
	DEV,
	}

Right below it, I find a function called env_from_str

leptos/leptos_config/src/lib.rs

Lines 172 to 182 in 8573f22

	fn env_from_str(input: &str) -> Result<Env, LeptosConfigError> {
	let sanitized = input.to_lowercase();
	match sanitized.as_ref() {
	"dev" | "development" => Ok(Env::DEV),
	"prod" | "production" => Ok(Env::PROD),
	_ => Err(LeptosConfigError::EnvVarError(format!(
	"{input} is not a supported environment. Use either `dev` or \
	`production`.",
	))),
	}
	}

This shows me that there are four options for the value: "dev" or "development" (same thing) and "prod" or "production" (same thing).

So the correct answer is LEPTOS_ENV=(one of those four)

AND NOTE: To the best of my knowledge, this setting is not used anywhere in Leptos itself. It exists solely in case you need to distinguish between dev and prod environments (as distinct from debug and release builds) anywhere in your app, and want to be able to conveniently specify that with an env variable and pull it out of the LeptosOptions struct that other config data is packed into.

Does that help?

[saikatdas0790]

Yes, thank you so much. That was succinct and instructive ❤️