better error handling using anyhow

Cargo.lock

@@ -20,6 +20,12 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "anyhow"
+version = "1.0.100"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a23eb6b1614318a8071c9b2521f36b424b2c83db5eb3a0fead4a6c0809af6e61"
+
 [[package]]
 name = "askama"
 version = "0.14.0"
@@ -812,6 +818,7 @@ checksum = "0bf256ce5efdfa370213c1dabab5935a12e49f2c58d15e9eac2870d3b4f27263"
 name = "task_counter"
 version = "0.1.0"
 dependencies = [
+ "anyhow",
  "askama",
  "axum",
  "chrono",

Cargo.toml

@@ -4,6 +4,7 @@ version = "0.1.0"
 edition = "2024"
 
 [dependencies]
+anyhow = "1.0.100"
 askama = "0.14.0"
 axum = "0.8.6"
 chrono = "0.4.42"

src/main.rs

@@ -5,7 +5,7 @@ use axum::{
     Router,
     extract::{MatchedPath, Path, State},
     http::{Request, StatusCode},
-    response::Html,
+    response::{Html, IntoResponse, Response},
     routing::{get, post},
 };
 use parking_lot::Mutex;
@@ -80,7 +80,7 @@ impl Food {
 struct PreparedStatements {}
 
 impl<'conn> PreparedStatements {
-    fn check(conn: &Connection) -> rusqlite::Result<Self> {
+    fn check(conn: &Connection) -> anyhow::Result<Self> {
         conn.prepare_cached(include_str!("increase.sql"))?;
         conn.prepare_cached(include_str!("decrease.sql"))?;
         conn.prepare_cached(include_str!("get_food.sql"))?;
@@ -121,10 +121,35 @@ impl<'conn> PreparedStatements {
     }
 }
 
+// Make our own error that wraps `anyhow::Error`.
+struct AppError(anyhow::Error);
+
+// Tell axum how to convert `AppError` into a response.
+impl IntoResponse for AppError {
+    fn into_response(self) -> Response {
+        (
+            StatusCode::INTERNAL_SERVER_ERROR,
+            format!("Something went wrong: {}", self.0),
+        )
+            .into_response()
+    }
+}
+
+// This enables using `?` on functions that return `Result<_, anyhow::Error>` to turn them into
+// `Result<_, AppError>`. That way you don't need to do that manually.
+impl<E> From<E> for AppError
+where
+    E: Into<anyhow::Error>,
+{
+    fn from(err: E) -> Self {
+        Self(err.into())
+    }
+}
+
 type ConnState = Arc<Mutex<Connection>>;
 
-fn get_version(tx: &Transaction) -> rusqlite::Result<usize> {
-    tx.query_one(include_str!("get_version.sql"), (), |row| row.get(0))
+fn get_version(tx: &Transaction) -> anyhow::Result<usize> {
+    Ok(tx.query_one(include_str!("get_version.sql"), (), |row| row.get(0))?)
 }
 
 fn get_migrations() -> [&'static str; 4] {
@@ -136,7 +161,7 @@ fn get_migrations() -> [&'static str; 4] {
     ]
 }
 
-fn do_migrations(conn: &mut Connection) -> rusqlite::Result<()> {
+fn do_migrations(conn: &mut Connection) -> anyhow::Result<()> {
     let migrations = get_migrations();
     let num_migrations = migrations.len();
     let tx = conn.transaction()?;
@@ -198,7 +223,7 @@ fn app(conn: Connection) -> axum::Router {
 }
 
 #[tokio::main]
-async fn main() -> Result<(), std::io::Error> {
+async fn main() -> anyhow::Result<()> {
     tracing_subscriber::registry()
         .with(
             tracing_subscriber::EnvFilter::try_from_default_env().unwrap_or_else(|_| {
@@ -239,10 +264,11 @@ async fn main() -> Result<(), std::io::Error> {
             .local_addr()
             .expect("failed to get local listening address")
     );
-    axum::serve(listener, app).await
+    axum::serve(listener, app).await?;
+    Ok(())
 }
 
-fn get_foods(conn: &ConnState) -> rusqlite::Result<Vec<Food>> {
+fn get_foods(conn: &ConnState) -> anyhow::Result<Vec<Food>> {
     let conn = conn.lock();
     let mut stmt = PreparedStatements::get_foods(&conn);
     let foods: Vec<_> = stmt
@@ -252,7 +278,7 @@ fn get_foods(conn: &ConnState) -> rusqlite::Result<Vec<Food>> {
     Ok(foods)
 }
 
-fn get_sum(conn: &Arc<Mutex<Connection>>) -> rusqlite::Result<Sum> {
+fn get_sum(conn: &Arc<Mutex<Connection>>) -> anyhow::Result<Sum> {
     let conn = conn.lock();
     let mut stmt = PreparedStatements::get_sum(&conn);
     let sum = stmt.query_one((), |row| {
@@ -272,22 +298,15 @@ fn get_date() -> String {
     date
 }
 
-async fn root(State(conn): State<ConnState>) -> Result<Html<String>, StatusCode> {
-    let foods = get_foods(&conn).map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?;
-    let sum = get_sum(&conn).map_err(|e| {
-        error!(?e);
-        StatusCode::INTERNAL_SERVER_ERROR
-    })?;
+async fn root(State(conn): State<ConnState>) -> Result<Html<String>, AppError> {
+    let foods = get_foods(&conn)?;
+    let sum = get_sum(&conn)?;
     let date = get_date();
     let index = IndexTemplate { foods, sum, date };
-    Ok(Html(
-        index
-            .render()
-            .map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?,
-    ))
+    Ok(Html(index.render()?))
 }
 
-fn do_increase(conn: &Arc<Mutex<Connection>>, id: i32) -> rusqlite::Result<()> {
+fn do_increase(conn: &Arc<Mutex<Connection>>, id: i32) -> anyhow::Result<()> {
     let conn = conn.lock();
     let mut stmt = PreparedStatements::increase(&conn);
     let new: i32 = stmt.query_one((id,), |row| row.get(0))?;
@@ -295,7 +314,7 @@ fn do_increase(conn: &Arc<Mutex<Connection>>, id: i32) -> rusqlite::Result<()> {
     Ok(())
 }
 
-fn get_food(conn: &Arc<Mutex<Connection>>, id: i32) -> rusqlite::Result<Food> {
+fn get_food(conn: &Arc<Mutex<Connection>>, id: i32) -> anyhow::Result<Food> {
     let conn = conn.lock();
     let mut stmt = PreparedStatements::get_food(&conn);
     let food = stmt.query_one((id,), Food::from_row)?;
@@ -306,20 +325,16 @@ fn get_food(conn: &Arc<Mutex<Connection>>, id: i32) -> rusqlite::Result<Food> {
 async fn increase(
     State(conn): State<Arc<Mutex<Connection>>>,
     Path(id): Path<i32>,
-) -> Result<Html<String>, StatusCode> {
-    do_increase(&conn, id).map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?;
-    let food = get_food(&conn, id).map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?;
-    let sum = get_sum(&conn).map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?;
+) -> Result<Html<String>, AppError> {
+    do_increase(&conn, id)?;
+    let food = get_food(&conn, id)?;
+    let sum = get_sum(&conn)?;
     let date = get_date();
     let update = FoodUpdateTemplate { food, sum, date };
-    Ok(Html(
-        update
-            .render()
-            .map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?,
-    ))
+    Ok(Html(update.render()?))
 }
 
-fn do_decrease(conn: &Arc<Mutex<Connection>>, id: i32) -> rusqlite::Result<()> {
+fn do_decrease(conn: &Arc<Mutex<Connection>>, id: i32) -> anyhow::Result<()> {
     let conn = conn.lock();
     let mut stmt = PreparedStatements::decrease(&conn);
     let new: i32 = stmt.query_one((id,), |row| row.get(0))?;
@@ -330,20 +345,16 @@ fn do_decrease(conn: &Arc<Mutex<Connection>>, id: i32) -> rusqlite::Result<()> {
 async fn decrease(
     State(conn): State<Arc<Mutex<Connection>>>,
     Path(id): Path<i32>,
-) -> Result<Html<String>, StatusCode> {
-    do_decrease(&conn, id).map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?;
-    let food = get_food(&conn, id).map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?;
-    let sum = get_sum(&conn).map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?;
+) -> Result<Html<String>, AppError> {
+    do_decrease(&conn, id)?;
+    let food = get_food(&conn, id)?;
+    let sum = get_sum(&conn)?;
     let date = get_date();
     let update = FoodUpdateTemplate { food, sum, date };
-    Ok(Html(
-        update
-            .render()
-            .map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?,
-    ))
+    Ok(Html(update.render()?))
 }
 
-fn do_set(conn: &Arc<Mutex<Connection>>, id: i32, amount: i32) -> rusqlite::Result<()> {
+fn do_set(conn: &Arc<Mutex<Connection>>, id: i32, amount: i32) -> anyhow::Result<()> {
     let conn = conn.lock();
     let mut stmt = PreparedStatements::set(&conn);
     let new: i32 = stmt.query_one((id, amount), |row| row.get(0))?;
@@ -354,15 +365,11 @@ fn do_set(conn: &Arc<Mutex<Connection>>, id: i32, amount: i32) -> rusqlite::Resu
 async fn set(
     State(conn): State<Arc<Mutex<Connection>>>,
     Path((id, amount)): Path<(i32, i32)>,
-) -> Result<Html<String>, StatusCode> {
-    do_set(&conn, id, amount).map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?;
-    let food = get_food(&conn, id).map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?;
-    let sum = get_sum(&conn).map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?;
+) -> Result<Html<String>, AppError> {
+    do_set(&conn, id, amount)?;
+    let food = get_food(&conn, id)?;
+    let sum = get_sum(&conn)?;
     let date = get_date();
     let update = FoodUpdateTemplate { food, sum, date };
-    Ok(Html(
-        update
-            .render()
-            .map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?,
-    ))
+    Ok(Html(update.render()?))
 }