Handle errors more gracefully than panicking

Cargo.lock

@@ -32,6 +32,12 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "anyhow"
+version = "1.0.65"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "98161a4e3e2184da77bb14f02184cdd111e83bbbcc9979dfee3c44b9a85f5602"
+
 [[package]]
 name = "async-channel"
 version = "1.6.1"
@@ -2303,6 +2309,7 @@ dependencies = [
 name = "ynabifier"
 version = "0.1.0"
 dependencies = [
+ "anyhow",
  "async-imap",
  "async-native-tls",
  "async-std",

Cargo.toml

@@ -24,6 +24,7 @@ chrono = "0.4.22"
 regex = "1.6"
 reqwest = { version = "0.11.12", features = ["json"] }
 url = "2.2"
+anyhow = "1.0"
 
 # For annoying reasons, we must pin exactly the same versions as async-imap if we want to use
 # their types.

src/email/inbox.rs

@@ -190,9 +190,15 @@ where
             debug!("idling");
             let sequence_number = Self::idle_for_email(idle_handle).await?;
             debug!("got email");
-            // TODO: handle these failures
-            sender.send(sequence_number).await.expect("failed to send");
-            debug!("sent");
+            let send_res = sender.send(sequence_number).await;
+            if let Err(err) = send_res {
+                error!(
+                    "Successfully fetched, but failed to dispatch email with sequence number {}: {}",
+                    sequence_number, err
+                );
+            } else {
+                debug!("sent");
+            }
         }
         debug!("done");
 

src/main.rs

@@ -3,7 +3,7 @@ extern crate log;
 
 use futures::{stream::StreamExt, Future};
 use log::LevelFilter;
-use std::{fs::File, sync::Arc};
+use std::{fs::File, process, sync::Arc};
 use tokio::runtime::Runtime;
 use ynabifier::parse::Transaction;
 use ynabifier::{
@@ -14,39 +14,28 @@ use ynabifier::{
 };
 
 fn main() {
-    let config_file = File::open("config.yml").expect("failed to open config file");
-    let config =
-        serde_yaml::from_reader::<_, Config>(config_file).expect("failed to parse config file");
+    let config_res = load_config("config.yml");
+    if let Err(err) = config_res {
+        eprintln!("Failed to load configuration: {}", err);
+        process::exit(1);
+    }
 
-    setup_logger(config.log_level()).expect("failed to seutp logger");
+    let config = config_res.unwrap();
+    if let Err(err) = setup_logger(config.log_level()) {
+        eprintln!("Failed to setup logger: {}", err);
+        process::exit(1);
+    }
 
-    let runtime = Runtime::new().expect("failed to create runtime");
-    runtime.block_on(async move {
-        let ynab_client = YNABClient::new(config.ynab().personal_access_token().to_string());
-        let mut stream =
-            ynabifier::stream_new_messages(Arc::new(TokioSpawner), config.imap().clone())
-                .await
-                .expect("failed to setup stream");
+    if let Err(err) = listen_for_transactions(&config) {
+        error!("Failed to listen for transaction emails: {}", err);
+        process::exit(2);
+    }
+}
 
-        let accounts = config.ynab().accounts();
-        while let Some(msg) = stream.next().await {
-            if let Some((account, transaction)) = try_parse_email(accounts.iter(), &msg) {
-                info!(
-                    "Parsed transaction for {} to {} with parser {}",
-                    transaction.amount(),
-                    transaction.payee(),
-                    account.parser_name(),
-                );
-                submit_transaction(
-                    &ynab_client,
-                    &transaction,
-                    config.ynab().budeget_id(),
-                    account.id(),
-                )
-                .await;
-            }
-        }
-    });
+fn load_config(filename: &str) -> Result<Config, anyhow::Error> {
+    let config_file = File::open(filename)?;
+    let config = serde_yaml::from_reader(config_file)?;
+    Ok(config)
 }
 
 fn setup_logger(log_level: LevelFilter) -> Result<(), fern::InitError> {
@@ -68,6 +57,36 @@ fn setup_logger(log_level: LevelFilter) -> Result<(), fern::InitError> {
     Ok(())
 }
 
+fn listen_for_transactions(config: &Config) -> Result<(), anyhow::Error> {
+    let runtime = Runtime::new()?;
+    runtime.block_on(async move {
+        let ynab_client = YNABClient::new(config.ynab().personal_access_token().to_string());
+        let mut stream =
+            ynabifier::stream_new_messages(Arc::new(TokioSpawner), config.imap().clone()).await?;
+
+        let accounts = config.ynab().accounts();
+        while let Some(msg) = stream.next().await {
+            if let Some((account, transaction)) = try_parse_email(accounts.iter(), &msg) {
+                info!(
+                    "Parsed transaction for {} to {} with parser {}",
+                    transaction.amount(),
+                    transaction.payee(),
+                    account.parser_name(),
+                );
+                submit_transaction(
+                    &ynab_client,
+                    &transaction,
+                    config.ynab().budeget_id(),
+                    account.id(),
+                )
+                .await;
+            }
+        }
+
+        Ok(())
+    })
+}
+
 fn try_parse_email<'a, I>(ynab_accounts: I, msg: &Message) -> Option<(&'a YNABAccount, Transaction)>
 where
     I: Iterator<Item = &'a YNABAccount>,