feat(backend): add thiserror-based error handling

Introduce AppError enum to replace panic-based error handling in executable loading and state management. Adds proper error propagation with descriptive error messages for missing executables, key patterns, and environment variables.

Cargo.lock

@@ -359,6 +359,7 @@ dependencies = [
  "salvo",
  "serde",
  "serde_json",
+ "thiserror 2.0.17",
  "tokio",
  "tokio-stream",
  "tracing",

Justfile

@@ -44,12 +44,12 @@ frontend-build:
 # Development server with hot reload
 dev:
     @echo "Starting development server..."
-    cargo watch -x run
+    cargo watch -x run --bin backend
 
 # Simple development run (no hot reload)
 run:
     @echo "Starting server..."
-    cargo run
+    cargo run --bin backend
 
 # Build release
 build:

backend/Cargo.toml

@@ -19,6 +19,7 @@ reqwest = { workspace = true, features = ["json", "rustls-tls"] }
 salvo.workspace = true
 serde.workspace = true
 serde_json.workspace = true
+thiserror = "2.0.17"
 tokio.workspace = true
 tokio-stream.workspace = true
 tracing.workspace = true

backend/src/errors.rs

@@ -0,0 +1,19 @@
+use std::path::PathBuf;
+use thiserror::Error;
+
+pub type Result<T> = std::result::Result<T, AppError>;
+
+#[derive(Debug, Error)]
+pub enum AppError {
+    #[error("executable not found at '{path}'")]
+    ExecutableNotFound { path: PathBuf },
+
+    #[error("key pattern not found in executable '{name}'")]
+    KeyPatternNotFound { name: String },
+
+    #[error("missing required environment variable '{name}'")]
+    MissingEnvVar { name: String },
+
+    #[error("configuration error: {message}")]
+    Config { message: String },
+}

backend/src/lib.rs

@@ -1,4 +1,5 @@
 pub mod config;
+pub mod errors;
 pub mod handlers;
 pub mod models;
 pub mod railway;

backend/src/main.rs

@@ -60,9 +60,16 @@ async fn main() {
         }
     }
 
-    store.add_executable("Windows", "./demo.exe");
-    store.add_executable("Linux", "./demo-linux");
-    // store.add_executable("MacOS", "./demo-macos");
+    for (exe_type, exe_path) in [
+        ("Windows", "./demo.exe"),
+        ("Linux", "./demo-linux"),
+        // ("MacOS", "./demo-macos"),
+    ] {
+        if let Err(e) = store.add_executable(exe_type, exe_path) {
+            tracing::error!("{}", e);
+            std::process::exit(1);
+        }
+    }
 
     drop(store); // critical: Drop the lock to avoid deadlock, otherwise the server will hang
 

backend/src/state.rs

@@ -1,10 +1,11 @@
 use std::collections::HashMap;
-use std::path;
+use std::path::{Path, PathBuf};
 use std::sync::LazyLock;
 
 use salvo::{http::cookie::Cookie, Response};
 use tokio::sync::Mutex;
 
+use crate::errors::{AppError, Result};
 use crate::models::{BuildLogs, Executable, ExecutableJson, Session};
 
 pub static STORE: LazyLock<Mutex<State>> = LazyLock::new(|| Mutex::new(State::new()));
@@ -27,30 +28,49 @@ impl State {
         }
     }
 
-    pub fn add_executable(&mut self, exe_type: &str, exe_path: &str) {
-        let data = std::fs::read(exe_path).expect("Unable to read file");
+    pub fn add_executable(&mut self, exe_type: &str, exe_path: &str) -> Result<()> {
+        let path = Path::new(exe_path);
+
+        let data = std::fs::read(path).map_err(|_| AppError::ExecutableNotFound {
+            path: PathBuf::from(exe_path),
+        })?;
 
         let pattern = "a".repeat(1024);
-        let key_start = Executable::search_pattern(&data, pattern.as_bytes(), 0).unwrap();
+        let name = path
+            .file_stem()
+            .and_then(|s| s.to_str())
+            .unwrap_or_default()
+            .to_string();
+
+        let key_start =
+            Executable::search_pattern(&data, pattern.as_bytes(), 0).ok_or_else(|| {
+                AppError::KeyPatternNotFound {
+                    name: name.clone(),
+                }
+            })?;
         let key_end = key_start + pattern.len();
 
-        let path = path::Path::new(&exe_path);
-        let name = path.file_stem().unwrap().to_str().unwrap();
-        let extension = match path.extension() {
-            Some(s) => s.to_str().unwrap(),
-            None => "",
-        };
+        let extension = path
+            .extension()
+            .and_then(|s| s.to_str())
+            .unwrap_or_default()
+            .to_string();
 
         let exe = Executable {
             data,
-            filename: path.file_name().unwrap().to_str().unwrap().to_string(),
-            name: name.to_string(),
-            extension: extension.to_string(),
+            filename: path
+                .file_name()
+                .and_then(|s| s.to_str())
+                .unwrap_or_default()
+                .to_string(),
+            name,
+            extension,
             key_start,
             key_end,
         };
 
         self.executables.insert(exe_type.to_string(), exe);
+        Ok(())
     }
 
     pub async fn new_session(&mut self, res: &mut Response) -> u32 {