refactor: use anyhow for error handling

Cargo.lock

@@ -9,6 +9,12 @@ dependencies = [
  "winapi 0.3.9",
 ]
 
+[[package]]
+name = "anyhow"
+version = "1.0.38"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "afddf7f520a80dbf76e6f50a35bca42a2331ef227a28b3b6dc5c2e2338d114b1"
+
 [[package]]
 name = "async-trait"
 version = "0.1.42"
@@ -1297,6 +1303,7 @@ checksum = "1a143597ca7c7793eff794def352d41792a93c481eb1042423ff7ff72ba2c31f"
 name = "webldappasswd"
 version = "0.1.0"
 dependencies = [
+ "anyhow",
  "clap",
  "handlebars",
  "ldap3",

Cargo.toml

@@ -9,6 +9,7 @@ lto = true
 codegen-units = 1
 
 [dependencies]
+anyhow = "1.0"
 clap = "2.33"
 handlebars = "3.5"
 serde = "1.0"

README.md

@@ -70,6 +70,7 @@ WebLDAPPasswd is published by Philipp Matthias Schäfer
 WebLDAPPasswd directly depends on the following Rust libraries all published by
 their copyright holders under the MIT License:
 
+* [*anyhow*](https://github.com/dtolnay/anyhow)
 * [*clap*](https://clap.rs)
 * [*serde*](https://serde.rs)
 * [*serde_derive*](https://serde.rs)

src/config.rs

@@ -1,12 +1,11 @@
 use std::io::BufReader;
 use std::fs::File;
 
+use anyhow::{Context, Result};
 use handlebars::Handlebars;
 use serde_derive::Deserialize;
 use serde_json::json;
 
-use crate::exit::exit_with_error;
-
 fn default_ldap_url() -> String {
     "ldap://localhost".to_string()
 }
@@ -33,24 +32,17 @@ pub struct Config {
     pub port: u16,
 }
 
-pub fn check_config(config: Config) -> Config {
-    let hb = Handlebars::new();
+pub fn load_config(file_path: &str) -> Result<Config> {
+    let file = File::open(file_path).
+        with_context(|| format!("Failed to open configuration file '{}'", file_path))?;
 
-    if let Some(e) = hb.render_template(&config.dn, &json!({"username" : "foo"})).err() {
-        exit_with_error(&format!("Failed to parse 'dn' ({}) in configuration file: {}", config.dn, e))
-    };
+    let config: Config = serde_json::from_reader(BufReader::new(file))
+        .with_context(|| format!("Failed to parse configuration file '{}'", file_path))?;
 
-    config
-}
-
-pub fn load_config(file_path: &str) -> Config {
-    let file = match File::open(file_path) {
-        Ok(file) => file,
-        Err(_) => exit_with_error(&format!("Failed to open configuration file '{}'", file_path))
-    };
-
-    match serde_json::from_reader(BufReader::new(file)) {
-        Ok(config) => check_config(config),
-        Err(_) => exit_with_error(&format!("Failed to parse configuration file '{}'", file_path))
-    }
+    Handlebars::new()
+        .render_template(&config.dn, &json!({"username" : "foo"}))
+        .map(|_| ())
+        .with_context(|| format!("Failed to parse DN ({}) in configuration file '{}'", config.dn, file_path))?;
+
+    Ok(config)
 }

src/exit.rs

@@ -1,4 +0,0 @@
-pub fn exit_with_error(message: &str) -> ! {
-    eprintln!("{}", message);
-    std::process::exit(-1)
-}

src/main.rs

@@ -2,19 +2,18 @@
 
 mod api;
 mod config;
-mod exit;
 mod r#static;
 
+use anyhow::{Context, Result};
 use clap::{Arg, App, crate_version};
 use rocket::routes;
 use rocket::config::{Config, Environment};
 
 use crate::config::load_config;
-use crate::exit::exit_with_error;
 
 const DEFAULT_CONFIG_FILE_PATH: &str = "/etc/webldappasswd/config.json";
 
-fn main() {
+fn main() -> Result<()> {
     let matches = App::new("WebLDAPPasswd")
         .version(crate_version!())
         .arg(Arg::with_name("config")
@@ -29,16 +28,13 @@ fn main() {
         .value_of("config")
         .unwrap_or(DEFAULT_CONFIG_FILE_PATH);
 
-    let config = load_config(config_file_path);
+    let config = load_config(config_file_path)?;
 
-    let rocket_config_builder = Config::build(Environment::Production)
+    let rocket_config = Config::build(Environment::Production)
         .address(&config.host)
-        .port(config.port);
-
-    let rocket_config = match rocket_config_builder.finalize() {
-        Ok(config) => config,
-        Err(e) => exit_with_error(&format!("Bad host address ({}) in configuration file: {}", config.host, e)),
-    };
+        .port(config.port)
+        .finalize()
+        .with_context(|| format!("Bad host address ({}) in configuration file '{}'", config.host, config_file_path))?;
 
     rocket::custom(rocket_config)
         .mount("/", routes![r#static::index,
@@ -51,4 +47,6 @@ fn main() {
                             api::update])
         .manage(config)
         .launch();
+
+    Ok(())
 }