clippy::option_env_unwrap: this will panic at run-time if the environment variable doesn't exist at compile-time

What you see

error: this will panic at run-time if the environment variable doesn't exist at compile-time
 --> main.rs:3:9
  |
3 | let _ = option_env!("HOME").unwrap();
  |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = help: consider using the `env!` macro instead
  = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#option_env_unwrap
  = note: `#[deny(clippy::option_env_unwrap)]` on by default

Real output of Clippy 0.1.99 (Rust 1.99) on the example below. Names and line numbers in yours will differ.

Does it matter?

Unwrapping the result of option_env! will panic at run-time if the environment variable doesn’t exist, whereas env! catches it at compile-time.

Code that is almost certainly wrong. Denied by default: the build fails until you fix it or allow it.

How to fix it

Clippy does not fix this one automatically. Change the code by hand:

Flagged

let _ = option_env!("HOME").unwrap();

Write this instead

let _ = env!("HOME");

Turn it off, or on

Allow it where it does not fit your code, as narrowly as you can:

#[allow(clippy::option_env_unwrap)]
fn my_function() { /* ... */ }

[lints.clippy]
option_env_unwrap = "allow"

cargo clippy -- -A clippy::option-env-unwrap

The [lints] table needs Rust 1.74 or newer. In a workspace, put it under [workspace.lints.clippy] and add [lints] workspace = true to each member.