From: Carl Worth <cworth@cworth.org>
Date: Tue, 10 Mar 2026 15:08:01 +0000 (-0700)
Subject: Switch from expect to map_err.
X-Git-Url: https://git.cworth.org/git?a=commitdiff_plain;h=556edb7edc52dac4280361ccbd7da3f178338350;p=rust-learning

Switch from expect to map_err.

This lets us make a clean exit rather than triggering a panic, (which
has some extra noise and suggests something more exceptional than we
really want here).

Note our message is reworded slightly since map_err doesn't give us
full control of the string. It emits:

	Error: "<our-string>"

so we don't want to start our string with "Error" as that would look
redundant.

I don't love not having full control of the error message, but still,
I think it is a reasonable compromise given how clean the code is with
.map_err.
---

diff --git a/src/main.rs b/src/main.rs
index 657e481..7123ed3 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -15,7 +15,7 @@ async fn main() -> Result<(), Box<dyn Error>> {
 
     let config_path = std::path::Path::new(&args[1]);
     let config = config::load_config(config_path)
-        .expect(format!("Error loading config file {}", args[1]).as_str());
+        .map_err(|e| format!("Failed to open config file {}: {}", args[1], e))?;
 
     eprintln!("Race: {}", config.name);