improve logging around config loading

example.env

@@ -6,6 +6,8 @@ AUTH.REDIRECT_URL=http://localhost:3000/auth/callback
 AUTH.AUTH_URL=https://example.com/authorize
 AUTH.TOKEN_URL=https://example.com/token
 AUTH.USERINFO_URL=https://example.com/userinfo
+# The .env parser (dotenvy) requires quotes around any value with spaces. Note
+# that in this regard it is incompatible with Docker's --env-file parser.
 EMAIL.VERIFICATION_FROM=no-reply@shout.dev
 EMAIL.MESSAGE_FROM=no-reply@shout.dev
 EMAIL.SMTP.SERVER=smtp.example.com

src/main.rs

@@ -57,12 +57,12 @@ enum Commands {
 
 #[tokio::main]
 async fn main() {
-    let settings = Settings::load().unwrap();
-
     tracing_subscriber::fmt()
         .with_env_filter(EnvFilter::from_default_env())
         .init();
 
+    let settings = Settings::load().unwrap();
+
     let cli = Cli::parse();
 
     let database_url = settings.database_url.clone();

src/settings.rs

@@ -1,3 +1,4 @@
+use anyhow::{Context as _, Result};
 use axum::extract::FromRef;
 use config::{Config, ConfigError, Environment};
 use dotenvy::dotenv;
@@ -78,14 +79,29 @@ pub struct SlackSettings {
 }
 
 impl Settings {
-    pub fn load() -> Result<Self, ConfigError> {
-        if let Err(err) = dotenv() {
-            tracing::warn!("Couldn't load .env file: {:?}", err);
+    pub fn load() -> Result<Self> {
+        match dotenv() {
+            Err(err) => {
+                if err.not_found() {
+                    tracing::info!("no .env file found");
+                } else {
+                    return Err(err).context("dotenvy error");
+                }
+            }
+            Ok(pathbuf) => {
+                tracing::info!(
+                    "using env file {}",
+                    pathbuf
+                        .to_str()
+                        .ok_or(anyhow::anyhow!("pathbuf is not valid unicode"))?
+                );
+            }
         }
         let s = Config::builder()
             .add_source(Environment::default())
-            .build()?;
-        s.try_deserialize()
+            .build()
+            .context("config error")?;
+        Ok(s.try_deserialize().context("deserialize error")?)
     }
 }