Merge pull request 'Implémentation d'une première approche de gestion des erreurs' (#52) from feat/handle_errors_rustly into main

# Détails

Implémente (en partie) les "bonnes pratiques" de gestion des erreurs Rust décrites dans le ticket #34

Cette PR se concentre beaucoup sur la gestion des erreurs "internes" et peu sur la manière dont on les expose à l'extérieur (API) ou les trace (dans des logs ou sur une app de suivi de logs). Une deuxième phase de travail sera nécessaire pour cela.

De même, les choix faits à de nombreux endroits sont très perfectibles :

- les noms des erreurs et enums ne semblent pas toujours au top
- certains "fallback" pourraient sans doute être améliorés
- certaines erreurs pourraient peut-être remonter + de contexte
- l'usage des librairies d'aide (anyhow et thiserror) ne sont pas uniformes

Cela dit, il est difficile de vraiment affiner ces éléments sans être dans des situations concrètes et réalistes. Je pense donc que c'est à force d'itération, en situation concrète et au fur et à mesure des relectures de code en DA que nous améliorerons ces points.

# Pourquoi ?

La gestion des erreurs en Rust est extrêmement puissante, permettant de construire des infrastructures où les "bugs" inattendus sont quasiment inexistants. Pour cela, un certain nombre de bonnes pratiques sont à suivre dans la gestion des retours d'erreurs des fonctions et des programmes à plus haut niveau.

# Documentation

CF #34

Reviewed-on: #52
Reviewed-by: theo <theo.lettermann@gmail.com>
Reviewed-by: kosssi <simon@p4pillon.org>
This commit is contained in:
Florian Briand 2024-08-22 20:56:12 +02:00
commit 32009e2f00
13 changed files with 387 additions and 158 deletions

4
Cargo.lock generated
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@ -92,6 +92,7 @@ dependencies = [
"notify 6.1.1", "notify 6.1.1",
"serde", "serde",
"systemfd", "systemfd",
"thiserror",
"tokio", "tokio",
"tower-http", "tower-http",
"tower-livereload", "tower-livereload",
@ -1066,6 +1067,7 @@ dependencies = [
"http", "http",
"tauri", "tauri",
"tauri-build", "tauri-build",
"thiserror",
"tokio", "tokio",
"tower", "tower",
] ]
@ -3915,8 +3917,10 @@ dependencies = [
name = "sesam-vitale" name = "sesam-vitale"
version = "0.1.0" version = "0.1.0"
dependencies = [ dependencies = [
"anyhow",
"dotenv", "dotenv",
"libc", "libc",
"thiserror",
] ]
[[package]] [[package]]

View File

@ -10,6 +10,7 @@ axum = "0.7.5"
listenfd = "1.0.1" listenfd = "1.0.1"
notify = "6.1.1" notify = "6.1.1"
serde = { version = "1.0.204", features = ["derive"] } serde = { version = "1.0.204", features = ["derive"] }
thiserror = "1.0.63"
tokio = { version = "1.39.1", features = ["macros", "rt-multi-thread"] } tokio = { version = "1.39.1", features = ["macros", "rt-multi-thread"] }
tower-http = { version = "0.5.2", features = ["fs"] } tower-http = { version = "0.5.2", features = ["fs"] }
tower-livereload = "0.9.3" tower-livereload = "0.9.3"

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@ -3,12 +3,23 @@ use axum::body::Body;
use axum::http::Request; use axum::http::Request;
use listenfd::ListenFd; use listenfd::ListenFd;
use notify::Watcher; use notify::Watcher;
use std::env;
use std::path::Path; use std::path::Path;
use std::{env, io};
use thiserror::Error;
use tokio::net::TcpListener; use tokio::net::TcpListener;
use tower_livereload::predicate::Predicate; use tower_livereload::predicate::Predicate;
use tower_livereload::LiveReloadLayer; use tower_livereload::LiveReloadLayer;
#[derive(Error, Debug)]
pub enum AppError {
#[error("Unable to bind to TCP listener")]
TCPListener(#[from] std::io::Error),
#[error("Error with the notify watcher")]
NotifyWatcher(#[from] notify::Error),
#[error("Missing environment variable {var}")]
MissingEnvVar { var: &'static str },
}
/// Nous filtrons les requêtes de `htmx` pour ne pas inclure le script _JS_ qui gère le rechargement /// Nous filtrons les requêtes de `htmx` pour ne pas inclure le script _JS_ qui gère le rechargement
/// Voir https://github.com/leotaku/tower-livereload/pull/3 /// Voir https://github.com/leotaku/tower-livereload/pull/3
#[derive(Copy, Clone)] #[derive(Copy, Clone)]
@ -20,44 +31,47 @@ impl<T> Predicate<Request<T>> for NotHtmxPredicate {
} }
const DEFAULT_LISTENER: &str = "localhost:3000"; const DEFAULT_LISTENER: &str = "localhost:3000";
async fn get_tcp_listener() -> TcpListener { async fn get_tcp_listener() -> Result<TcpListener, io::Error> {
let mut listenfd = ListenFd::from_env(); let mut listenfd = ListenFd::from_env();
match listenfd.take_tcp_listener(0).unwrap() { match listenfd.take_tcp_listener(0)? {
// if we are given a tcp listener on listen fd 0, we use that one // if we are given a tcp listener on listen fd 0, we use that one
Some(listener) => { Some(listener) => {
listener.set_nonblocking(true).unwrap(); listener.set_nonblocking(true)?;
TcpListener::from_std(listener).unwrap() Ok(TcpListener::from_std(listener)?)
} }
// otherwise fall back to local listening // otherwise fall back to local listening
None => TcpListener::bind(DEFAULT_LISTENER).await.unwrap(), None => Ok(TcpListener::bind(DEFAULT_LISTENER).await?),
} }
} }
fn get_livereload_layer(templates_path: &Path) -> LiveReloadLayer<NotHtmxPredicate> { fn get_livereload_layer(
templates_path: &Path,
) -> Result<LiveReloadLayer<NotHtmxPredicate>, notify::Error> {
let livereload = LiveReloadLayer::new(); let livereload = LiveReloadLayer::new();
let reloader = livereload.reloader(); let reloader = livereload.reloader();
let mut watcher = notify::recommended_watcher(move |_| reloader.reload()).unwrap(); let mut watcher = notify::recommended_watcher(move |_| reloader.reload())?;
watcher watcher.watch(templates_path, notify::RecursiveMode::Recursive)?;
.watch(templates_path, notify::RecursiveMode::Recursive) Ok(livereload.request_predicate::<Body, NotHtmxPredicate>(NotHtmxPredicate))
.unwrap();
livereload.request_predicate::<Body, NotHtmxPredicate>(NotHtmxPredicate)
} }
#[tokio::main] #[tokio::main]
async fn main() { async fn main() -> Result<(), AppError> {
let manifest_dir = env::var("CARGO_MANIFEST_DIR").unwrap(); let manifest_dir = env::var("CARGO_MANIFEST_DIR").map_err(|_| AppError::MissingEnvVar {
var: "CARGO_MANIFEST_DIR",
})?;
let assets_path = Path::new(&manifest_dir).join("assets"); let assets_path = Path::new(&manifest_dir).join("assets");
let templates_path = Path::new(&manifest_dir).join("templates"); let templates_path = Path::new(&manifest_dir).join("templates");
let livereload_layer = get_livereload_layer(&templates_path); let livereload_layer =
get_livereload_layer(&templates_path).map_err(AppError::NotifyWatcher)?;
let router = get_router(assets_path.as_path()).layer(livereload_layer); let router = get_router(assets_path.as_path()).layer(livereload_layer);
let listener: TcpListener = get_tcp_listener().await; let listener: TcpListener = get_tcp_listener().await.map_err(AppError::TCPListener)?;
println!("Listening on: http://{}", listener.local_addr().unwrap()); let local_addr = listener.local_addr().map_err(AppError::TCPListener)?;
println!("Listening on: http://{}", local_addr);
// Run the server with the router // Run the server with the router
axum::serve(listener, router.into_make_service()) axum::serve(listener, router.into_make_service()).await?;
.await Ok(())
.unwrap();
} }

View File

@ -21,4 +21,5 @@ tokio = "1.39.1"
app = { path = "../app" } app = { path = "../app" }
http = "1.1.0" http = "1.1.0"
bytes = "1.6.1" bytes = "1.6.1"
thiserror = "1.0.63"

View File

@ -1,21 +1,30 @@
use axum::body::{to_bytes, Body};
use axum::Router;
use bytes::Bytes; use bytes::Bytes;
use http::{request, response, Request, Response}; use http::{request, response, Request, Response};
use std::path::PathBuf; use std::path::PathBuf;
use std::sync::Arc; use std::sync::Arc;
use axum::body::{to_bytes, Body};
use axum::Router;
use tauri::path::BaseDirectory; use tauri::path::BaseDirectory;
use tauri::Manager; use tauri::Manager;
use thiserror::Error;
use tokio::sync::{Mutex, MutexGuard}; use tokio::sync::{Mutex, MutexGuard};
use tower::{Service, ServiceExt}; use tower::{Service, ServiceExt};
#[derive(Error, Debug)]
pub enum DesktopError {
#[error("Axum error:\n{0}")]
Axum(#[from] axum::Error),
#[error("Infallible error")]
Infallible(#[from] std::convert::Infallible),
}
/// Process requests sent to Tauri (with the `axum://` protocol) and handle them with Axum
/// When an error occurs, this function is expected to panic, which should result in a 500 error
/// being sent to the client, so we let the client handle the error recovering
async fn process_tauri_request( async fn process_tauri_request(
tauri_request: Request<Vec<u8>>, tauri_request: Request<Vec<u8>>,
mut router: MutexGuard<'_, Router>, mut router: MutexGuard<'_, Router>,
) -> Response<Vec<u8>> { ) -> Result<Response<Vec<u8>>, DesktopError> {
let (parts, body): (request::Parts, Vec<u8>) = tauri_request.into_parts(); let (parts, body): (request::Parts, Vec<u8>) = tauri_request.into_parts();
let axum_request: Request<Body> = Request::from_parts(parts, body.into()); let axum_request: Request<Body> = Request::from_parts(parts, body.into());
@ -23,17 +32,16 @@ async fn process_tauri_request(
.as_service() .as_service()
.ready() .ready()
.await .await
.expect("Failed to get ready service from router") .map_err(DesktopError::Infallible)?
.call(axum_request) .call(axum_request)
.await .await
.expect("Could not get response from router"); .map_err(DesktopError::Infallible)?;
let (parts, body): (response::Parts, Body) = axum_response.into_parts(); let (parts, body): (response::Parts, Body) = axum_response.into_parts();
let body: Bytes = to_bytes(body, usize::MAX).await.unwrap_or_default(); let body: Bytes = to_bytes(body, usize::MAX).await?;
let tauri_response: Response<Vec<u8>> = Response::from_parts(parts, body.into()); let tauri_response: Response<Vec<u8>> = Response::from_parts(parts, body.into());
Ok(tauri_response)
tauri_response
} }
#[cfg_attr(mobile, tauri::mobile_entry_point)] #[cfg_attr(mobile, tauri::mobile_entry_point)]
@ -43,7 +51,7 @@ pub fn run() {
let assets_path: PathBuf = app let assets_path: PathBuf = app
.path() .path()
.resolve("assets", BaseDirectory::Resource) .resolve("assets", BaseDirectory::Resource)
.expect("Path should be resolvable"); .expect("Assets path should be resolvable");
// Adds Axum router to application state // Adds Axum router to application state
// This makes it so we can retrieve it from any app instance (see bellow) // This makes it so we can retrieve it from any app instance (see bellow)
@ -60,8 +68,19 @@ pub fn run() {
// Spawn a new async task to process the request // Spawn a new async task to process the request
tauri::async_runtime::spawn(async move { tauri::async_runtime::spawn(async move {
let router = router.lock().await; let router = router.lock().await;
let response = process_tauri_request(request, router).await; match process_tauri_request(request, router).await {
responder.respond(response); Ok(response) => responder.respond(response),
Err(err) => {
let body = format!("Failed to process an axum:// request:\n{}", err);
responder.respond(
http::Response::builder()
.status(http::StatusCode::BAD_REQUEST)
.header(http::header::CONTENT_TYPE, "text/plain")
.body::<Vec<u8>>(body.into())
.expect("BAD_REQUEST response should be valid"),
)
}
}
}); });
}) })
.run(tauri::generate_context!()) .run(tauri::generate_context!())

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@ -4,8 +4,10 @@ version = "0.1.0"
edition = "2021" edition = "2021"
[dependencies] [dependencies]
anyhow = "1.0.86"
dotenv = "0.15" dotenv = "0.15"
libc = "0.2" libc = "0.2"
thiserror = "1.0.63"
[build-dependencies] [build-dependencies]
dotenv = "0.15" dotenv = "0.15"

View File

@ -5,7 +5,7 @@ use std::path::PathBuf;
fn main() { fn main() {
// Load the .env.build file for build-time environment variables // Load the .env.build file for build-time environment variables
let manifest_dir = env::var("CARGO_MANIFEST_DIR").unwrap(); let manifest_dir = env::var("CARGO_MANIFEST_DIR").expect("CARGO_MANIFEST_DIR must be set");
let manifest_path = PathBuf::from(manifest_dir); let manifest_path = PathBuf::from(manifest_dir);
dotenv::from_path(manifest_path.join(".env.build")).ok(); dotenv::from_path(manifest_path.join(".env.build")).ok();
@ -22,12 +22,13 @@ fn main() {
); );
// Add the SESAM_FSV_LIB_PATH to the linker search path // Add the SESAM_FSV_LIB_PATH to the linker search path
let fsv_lib_path = PathBuf::from(env::var("SESAM_FSV_LIB_PATH").unwrap()); let fsv_lib_path =
PathBuf::from(env::var("SESAM_FSV_LIB_PATH").expect("SESAM_FSV_LIB_PATH must be set"));
println!("cargo::rustc-link-search=native={}", fsv_lib_path.display()); println!("cargo::rustc-link-search=native={}", fsv_lib_path.display());
// Add the SESAM_FSV_LIB_PATH to the PATH environment variable // Add the SESAM_FSV_LIB_PATH to the PATH environment variable
if cfg!(target_os = "windows") { if cfg!(target_os = "windows") {
let path = env::var("PATH").unwrap_or(String::new()); let path = env::var("PATH").unwrap_or_default();
println!("cargo:rustc-env=PATH={};{}", fsv_lib_path.display(), path); println!("cargo:rustc-env=PATH={};{}", fsv_lib_path.display(), path);
} else if cfg!(target_os = "linux") { } else if cfg!(target_os = "linux") {
println!("cargo:rustc-env=LD_LIBRARY_PATH={}", fsv_lib_path.display()); println!("cargo:rustc-env=LD_LIBRARY_PATH={}", fsv_lib_path.display());
@ -36,7 +37,7 @@ fn main() {
// Link the SESAM_FSV_SSVLIB dynamic library // Link the SESAM_FSV_SSVLIB dynamic library
println!( println!(
"cargo::rustc-link-lib=dylib={}", "cargo::rustc-link-lib=dylib={}",
env::var("SESAM_FSV_SSVLIB").unwrap() env::var("SESAM_FSV_SSVLIB").expect("SESAM_FSV_SSVLIB must be set")
); );
// TODO : try `raw-dylib` instead of `dylib` on Windows to avoid the need of the `lib` headers compiled from the `def` // TODO : try `raw-dylib` instead of `dylib` on Windows to avoid the need of the `lib` headers compiled from the `def`
} }

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@ -1,9 +1,24 @@
use libc::{c_void, size_t}; use libc::{c_void, size_t};
use std::ffi::CString; use std::ffi::CString;
use std::ptr; use std::ptr;
use thiserror::Error;
use crate::libssv::SSV_LireCartePS; use crate::libssv::{self, SSV_LireCartePS};
use crate::ssv_memory::{decode_ssv_memory, Block}; use crate::ssv_memory::{decode_ssv_memory, Block, SSVMemoryError};
#[derive(Error, Debug)]
pub enum CartePSError {
#[error("Unknown (group, field) pair: ({group}, {field})")]
UnknownGroupFieldPair { group: u16, field: u16 },
#[error("CString creation error: {0}")]
CString(#[from] std::ffi::NulError),
#[error("Unable to get the last situation while parsing a CartePS")]
InvalidLastSituation,
#[error(transparent)]
SSVMemory(#[from] SSVMemoryError),
#[error(transparent)]
SSVLibErrorCode(#[from] libssv::LibSSVError),
}
#[derive(Debug, Default)] #[derive(Debug, Default)]
pub struct CartePS { pub struct CartePS {
@ -52,10 +67,10 @@ struct SituationPS {
habilitation_à_signer_un_lot: String, habilitation_à_signer_un_lot: String,
} }
pub fn lire_carte(code_pin: &str, lecteur: &str) -> Result<CartePS, String> { pub fn lire_carte(code_pin: &str, lecteur: &str) -> Result<CartePS, CartePSError> {
let resource_ps = CString::new(lecteur).expect("CString::new failed"); let resource_ps = CString::new(lecteur)?;
let resource_reader = CString::new("").expect("CString::new failed"); let resource_reader = CString::new("")?;
let card_number = CString::new(code_pin).expect("CString::new failed"); let card_number = CString::new(code_pin)?;
let mut buffer: *mut c_void = ptr::null_mut(); let mut buffer: *mut c_void = ptr::null_mut();
let mut size: size_t = 0; let mut size: size_t = 0;
@ -69,17 +84,32 @@ pub fn lire_carte(code_pin: &str, lecteur: &str) -> Result<CartePS, String> {
&mut size, &mut size,
); );
println!("SSV_LireCartePS result: {}", result); println!("SSV_LireCartePS result: {}", result);
if result != 0 {
return Err(libssv::LibSSVError::StandardErrorCode {
code: result,
function: "SSV_LireCartePS",
}
.into());
}
if !buffer.is_null() { if !buffer.is_null() {
hex_values = std::slice::from_raw_parts(buffer as *const u8, size); hex_values = std::slice::from_raw_parts(buffer as *const u8, size);
libc::free(buffer); libc::free(buffer);
} }
} }
let groups = decode_ssv_memory(hex_values, hex_values.len()); let groups =
decode_ssv_memory(hex_values, hex_values.len()).map_err(CartePSError::SSVMemory)?;
decode_carte_ps(groups) decode_carte_ps(groups)
} }
fn decode_carte_ps(groups: Vec<Block>) -> Result<CartePS, String> { fn get_last_mut_situation(carte_ps: &mut CartePS) -> Result<&mut SituationPS, CartePSError> {
carte_ps
.situations
.last_mut()
.ok_or(CartePSError::InvalidLastSituation)
}
fn decode_carte_ps(groups: Vec<Block>) -> Result<CartePS, CartePSError> {
let mut carte_ps = CartePS::default(); let mut carte_ps = CartePS::default();
for group in groups { for group in groups {
for field in group.content { for field in group.content {
@ -118,137 +148,99 @@ fn decode_carte_ps(groups: Vec<Block>) -> Result<CartePS, String> {
} }
(2..=16, 1) => { (2..=16, 1) => {
carte_ps.situations.push(SituationPS::default()); carte_ps.situations.push(SituationPS::default());
carte_ps get_last_mut_situation(&mut carte_ps)?
.situations
.last_mut()
.unwrap()
.numero_logique_de_la_situation_de_facturation_du_ps = field.content[0]; .numero_logique_de_la_situation_de_facturation_du_ps = field.content[0];
} }
(2..=16, 2) => { (2..=16, 2) => {
carte_ps.situations.last_mut().unwrap().mode_d_exercice = get_last_mut_situation(&mut carte_ps)?.mode_d_exercice =
String::from_utf8_lossy(field.content).to_string(); String::from_utf8_lossy(field.content).to_string();
} }
(2..=16, 3) => { (2..=16, 3) => {
carte_ps.situations.last_mut().unwrap().statut_d_exercice = get_last_mut_situation(&mut carte_ps)?.statut_d_exercice =
String::from_utf8_lossy(field.content).to_string(); String::from_utf8_lossy(field.content).to_string();
} }
(2..=16, 4) => { (2..=16, 4) => {
carte_ps.situations.last_mut().unwrap().secteur_d_activite = get_last_mut_situation(&mut carte_ps)?.secteur_d_activite =
String::from_utf8_lossy(field.content).to_string(); String::from_utf8_lossy(field.content).to_string();
} }
(2..=16, 5) => { (2..=16, 5) => {
carte_ps get_last_mut_situation(&mut carte_ps)?.type_d_identification_structure =
.situations
.last_mut()
.unwrap()
.type_d_identification_structure =
String::from_utf8_lossy(field.content).to_string(); String::from_utf8_lossy(field.content).to_string();
} }
(2..=16, 6) => { (2..=16, 6) => {
carte_ps get_last_mut_situation(&mut carte_ps)?.numero_d_identification_structure =
.situations
.last_mut()
.unwrap()
.numero_d_identification_structure =
String::from_utf8_lossy(field.content).to_string(); String::from_utf8_lossy(field.content).to_string();
} }
(2..=16, 7) => { (2..=16, 7) => {
carte_ps get_last_mut_situation(&mut carte_ps)?
.situations
.last_mut()
.unwrap()
.cle_du_numero_d_identification_structure = .cle_du_numero_d_identification_structure =
String::from_utf8_lossy(field.content).to_string(); String::from_utf8_lossy(field.content).to_string();
} }
(2..=16, 8) => { (2..=16, 8) => {
carte_ps get_last_mut_situation(&mut carte_ps)?.raison_sociale_structure =
.situations
.last_mut()
.unwrap()
.raison_sociale_structure =
String::from_utf8_lossy(field.content).to_string(); String::from_utf8_lossy(field.content).to_string();
} }
(2..=16, 9) => { (2..=16, 9) => {
carte_ps get_last_mut_situation(&mut carte_ps)?
.situations
.last_mut()
.unwrap()
.numero_d_identification_de_facturation_du_ps = .numero_d_identification_de_facturation_du_ps =
String::from_utf8_lossy(field.content).to_string(); String::from_utf8_lossy(field.content).to_string();
} }
(2..=16, 10) => { (2..=16, 10) => {
carte_ps get_last_mut_situation(&mut carte_ps)?
.situations
.last_mut()
.unwrap()
.cle_du_numero_d_identification_de_facturation_du_ps = .cle_du_numero_d_identification_de_facturation_du_ps =
String::from_utf8_lossy(field.content).to_string(); String::from_utf8_lossy(field.content).to_string();
} }
(2..=16, 11) => { (2..=16, 11) => {
carte_ps get_last_mut_situation(&mut carte_ps)?
.situations
.last_mut()
.unwrap()
.numero_d_identification_du_ps_remplaçant = .numero_d_identification_du_ps_remplaçant =
String::from_utf8_lossy(field.content).to_string(); String::from_utf8_lossy(field.content).to_string();
} }
(2..=16, 12) => { (2..=16, 12) => {
carte_ps get_last_mut_situation(&mut carte_ps)?
.situations
.last_mut()
.unwrap()
.cle_du_numero_d_identification_du_ps_remplaçant = .cle_du_numero_d_identification_du_ps_remplaçant =
String::from_utf8_lossy(field.content).to_string(); String::from_utf8_lossy(field.content).to_string();
} }
(2..=16, 13) => { (2..=16, 13) => {
carte_ps.situations.last_mut().unwrap().code_conventionnel = get_last_mut_situation(&mut carte_ps)?.code_conventionnel =
String::from_utf8_lossy(field.content).to_string(); String::from_utf8_lossy(field.content).to_string();
} }
(2..=16, 14) => { (2..=16, 14) => {
carte_ps.situations.last_mut().unwrap().code_specialite = get_last_mut_situation(&mut carte_ps)?.code_specialite =
String::from_utf8_lossy(field.content).to_string(); String::from_utf8_lossy(field.content).to_string();
} }
(2..=16, 15) => { (2..=16, 15) => {
carte_ps.situations.last_mut().unwrap().code_zone_tarifaire = get_last_mut_situation(&mut carte_ps)?.code_zone_tarifaire =
String::from_utf8_lossy(field.content).to_string(); String::from_utf8_lossy(field.content).to_string();
} }
(2..=16, 16) => { (2..=16, 16) => {
carte_ps.situations.last_mut().unwrap().code_zone_ik = get_last_mut_situation(&mut carte_ps)?.code_zone_ik =
String::from_utf8_lossy(field.content).to_string(); String::from_utf8_lossy(field.content).to_string();
} }
(2..=16, 17) => { (2..=16, 17) => {
carte_ps.situations.last_mut().unwrap().code_agrement_1 = get_last_mut_situation(&mut carte_ps)?.code_agrement_1 =
String::from_utf8_lossy(field.content).to_string(); String::from_utf8_lossy(field.content).to_string();
} }
(2..=16, 18) => { (2..=16, 18) => {
carte_ps.situations.last_mut().unwrap().code_agrement_2 = get_last_mut_situation(&mut carte_ps)?.code_agrement_2 =
String::from_utf8_lossy(field.content).to_string(); String::from_utf8_lossy(field.content).to_string();
} }
(2..=16, 19) => { (2..=16, 19) => {
carte_ps.situations.last_mut().unwrap().code_agrement_3 = get_last_mut_situation(&mut carte_ps)?.code_agrement_3 =
String::from_utf8_lossy(field.content).to_string(); String::from_utf8_lossy(field.content).to_string();
} }
(2..=16, 20) => { (2..=16, 20) => {
carte_ps get_last_mut_situation(&mut carte_ps)?.habilitation_à_signer_une_facture =
.situations
.last_mut()
.unwrap()
.habilitation_à_signer_une_facture =
String::from_utf8_lossy(field.content).to_string(); String::from_utf8_lossy(field.content).to_string();
} }
(2..=16, 21) => { (2..=16, 21) => {
carte_ps get_last_mut_situation(&mut carte_ps)?.habilitation_à_signer_un_lot =
.situations
.last_mut()
.unwrap()
.habilitation_à_signer_un_lot =
String::from_utf8_lossy(field.content).to_string(); String::from_utf8_lossy(field.content).to_string();
} }
_ => { _ => {
return Err(format!( return Err(CartePSError::UnknownGroupFieldPair {
"Unknown (group, field) pair: ({}, {})", group: group.id,
group.id, field.id field: field.id,
)) });
} }
} }
} }
@ -279,7 +271,7 @@ mod test_decode_carte_ps {
57, 53, 8, 48, 48, 50, 48, 50, 52, 49, 57, 1, 56, 0, 1, 48, 1, 49, 2, 53, 48, 2, 49, 57, 53, 8, 48, 48, 50, 48, 50, 52, 49, 57, 1, 56, 0, 1, 48, 1, 49, 2, 53, 48, 2, 49,
48, 2, 48, 48, 1, 48, 1, 48, 1, 48, 1, 49, 1, 49, 48, 2, 48, 48, 1, 48, 1, 48, 1, 48, 1, 49, 1, 49,
]; ];
let blocks = decode_ssv_memory(bytes, bytes.len()); let blocks = decode_ssv_memory(bytes, bytes.len()).unwrap();
let carte_ps = decode_carte_ps(blocks).unwrap(); let carte_ps = decode_carte_ps(blocks).unwrap();
assert_eq!(carte_ps.titulaire.type_de_carte_ps, "0"); assert_eq!(carte_ps.titulaire.type_de_carte_ps, "0");
@ -370,7 +362,7 @@ mod test_decode_carte_ps {
57, 53, 8, 48, 48, 50, 48, 50, 52, 49, 57, 1, 56, 0, 1, 48, 1, 49, 2, 53, 48, 2, 49, 57, 53, 8, 48, 48, 50, 48, 50, 52, 49, 57, 1, 56, 0, 1, 48, 1, 49, 2, 53, 48, 2, 49,
48, 2, 48, 48, 1, 48, 1, 48, 1, 48, 1, 49, 1, 49, 48, 2, 48, 48, 1, 48, 1, 48, 1, 48, 1, 49, 1, 49,
]; ];
let blocks = decode_ssv_memory(bytes, bytes.len()); let blocks = decode_ssv_memory(bytes, bytes.len()).unwrap();
let carte_ps = decode_carte_ps(blocks).unwrap(); let carte_ps = decode_carte_ps(blocks).unwrap();
assert_eq!(carte_ps.situations.len(), 3); assert_eq!(carte_ps.situations.len(), 3);

View File

@ -3,6 +3,13 @@
/// Low level bindings to the SSVLIB dynamic library. /// Low level bindings to the SSVLIB dynamic library.
// TODO : look for creating a dedicated *-sys crate : https://kornel.ski/rust-sys-crate // TODO : look for creating a dedicated *-sys crate : https://kornel.ski/rust-sys-crate
use libc::{c_char, c_ushort, c_void, size_t}; use libc::{c_char, c_ushort, c_void, size_t};
use thiserror::Error;
#[derive(Debug, Error)]
pub enum LibSSVError {
#[error("SSV library error in {function}: {code}")]
StandardErrorCode { code: u16, function: &'static str },
}
#[cfg_attr(target_os = "linux", link(name = "ssvlux64"))] #[cfg_attr(target_os = "linux", link(name = "ssvlux64"))]
#[cfg_attr(target_os = "windows", link(name = "ssvw64"))] #[cfg_attr(target_os = "windows", link(name = "ssvw64"))]

View File

@ -3,6 +3,8 @@ mod libssv;
mod ssv_memory; mod ssv_memory;
mod ssvlib_demo; mod ssvlib_demo;
fn main() { use anyhow::{Context, Result};
ssvlib_demo::demo();
fn main() -> Result<()> {
ssvlib_demo::demo().context("Error while running the SSV library demo")
} }

View File

@ -1,6 +1,33 @@
/// # SSV Memory /// # SSV Memory
/// Provide functions to manipulate raw memory from SSV library. /// Provide functions to manipulate raw memory from SSV library.
use std::convert::TryFrom; use std::convert::TryFrom;
use thiserror::Error;
#[derive(Debug, Error)]
pub enum BytesReadingError {
#[error("Empty bytes input")]
EmptyBytes,
#[error("Invalid memory: not enough bytes ({actual}) to read the expected size ({expected})")]
InvalidSize { expected: usize, actual: usize },
#[error("Invalid memory: size ({actual}) is expected to be less than {expected} bytes")]
SizeTooBig { expected: usize, actual: usize },
#[error("Invalid memory: not enough bytes to read the block id")]
InvalidBlockId(#[from] std::array::TryFromSliceError),
#[error("Error while reading field at offset {offset}")]
InvalidField {
source: Box<BytesReadingError>,
offset: usize,
},
}
#[derive(Debug, Error)]
pub enum SSVMemoryError {
#[error("Error while parsing block at offset {offset}")]
BlockParsing {
source: BytesReadingError,
offset: usize,
},
}
#[derive(PartialEq, Debug)] #[derive(PartialEq, Debug)]
struct ElementSize { struct ElementSize {
@ -9,13 +36,12 @@ struct ElementSize {
} }
// TODO : Est-ce qu'on pourrait/devrait définir un type custom pour représenter les tableaux de bytes ? // TODO : Est-ce qu'on pourrait/devrait définir un type custom pour représenter les tableaux de bytes ?
impl TryFrom<&[u8]> for ElementSize { impl TryFrom<&[u8]> for ElementSize {
type Error = &'static str; type Error = BytesReadingError;
fn try_from(bytes: &[u8]) -> Result<Self, Self::Error> { fn try_from(bytes: &[u8]) -> Result<Self, Self::Error> {
if bytes.is_empty() { if bytes.is_empty() {
return Err("Empty bytes input"); return Err(BytesReadingError::EmptyBytes);
} }
let mut element_size = ElementSize { size: 0, pad: 1 }; let mut element_size = ElementSize { size: 0, pad: 1 };
@ -30,9 +56,15 @@ impl TryFrom<&[u8]> for ElementSize {
// N are the 7 lower bits of the first byte // N are the 7 lower bits of the first byte
let size_bytes_len = (bytes[0] & 0b0111_1111) as usize; let size_bytes_len = (bytes[0] & 0b0111_1111) as usize;
if size_bytes_len > bytes.len() - 1 { if size_bytes_len > bytes.len() - 1 {
return Err("Invalid memory: not enough bytes to read the size"); return Err(BytesReadingError::InvalidSize {
expected: size_bytes_len,
actual: bytes.len() - 1,
});
} else if size_bytes_len > 4 { } else if size_bytes_len > 4 {
return Err("Invalid memory: size is too big"); return Err(BytesReadingError::SizeTooBig {
expected: 4,
actual: size_bytes_len,
});
} }
let size_bytes = &bytes[1..1 + size_bytes_len]; let size_bytes = &bytes[1..1 + size_bytes_len];
@ -54,15 +86,21 @@ pub struct Block<'a> {
pub content: Vec<Field<'a>>, pub content: Vec<Field<'a>>,
} }
impl<'a> From<&'a [u8]> for Block<'a> { impl<'a> TryFrom<&'a [u8]> for Block<'a> {
fn from(bytes: &'a [u8]) -> Self { type Error = BytesReadingError;
fn try_from(bytes: &'a [u8]) -> Result<Self, Self::Error> {
let mut offset = 0; let mut offset = 0;
let id = u16::from_be_bytes(bytes[..2].try_into().unwrap()); let id = u16::from_be_bytes(
bytes[..2]
.try_into()
.map_err(BytesReadingError::InvalidBlockId)?,
);
offset += 2; offset += 2;
let ElementSize { let ElementSize {
size: block_size, size: block_size,
pad, pad,
} = bytes[2..].try_into().unwrap(); } = bytes[2..].try_into()?;
offset += pad; offset += pad;
let raw_content = &bytes[offset..]; let raw_content = &bytes[offset..];
let mut field_offset = 0; let mut field_offset = 0;
@ -70,17 +108,22 @@ impl<'a> From<&'a [u8]> for Block<'a> {
let mut content = Vec::new(); let mut content = Vec::new();
let mut field_id = 1; let mut field_id = 1;
while field_offset < block_size { while field_offset < block_size {
let mut field: Field<'a> = raw_content[field_offset..].into(); let mut field: Field<'a> = raw_content[field_offset..].try_into().map_err(|err| {
BytesReadingError::InvalidField {
source: Box::new(err),
offset: field_offset,
}
})?;
field.id = field_id; field.id = field_id;
field_offset += field.size; field_offset += field.size;
field_id += 1; field_id += 1;
content.push(field); content.push(field);
} }
Block { Ok(Block {
id, id,
size: offset + block_size, size: offset + block_size,
content, content,
} })
} }
} }
@ -91,31 +134,41 @@ pub struct Field<'a> {
pub content: &'a [u8], pub content: &'a [u8],
} }
impl<'a> From<&'a [u8]> for Field<'a> { impl<'a> TryFrom<&'a [u8]> for Field<'a> {
fn from(bytes: &'a [u8]) -> Self { type Error = BytesReadingError;
let ElementSize { size, pad } = bytes.try_into().unwrap();
fn try_from(bytes: &'a [u8]) -> Result<Self, Self::Error> {
let ElementSize { size, pad } = bytes.try_into()?;
let contenu = &bytes[pad..pad + size]; let contenu = &bytes[pad..pad + size];
Field { Ok(Field {
id: 0, id: 0,
size: pad + size, size: pad + size,
content: contenu, content: contenu,
} })
} }
} }
pub fn decode_ssv_memory(bytes: &[u8], size: usize) -> Vec<Block> { pub fn decode_ssv_memory(bytes: &[u8], size: usize) -> Result<Vec<Block>, SSVMemoryError> {
let mut blocks: Vec<Block> = Vec::new(); let mut blocks: Vec<Block> = Vec::new();
let mut offset = 0; let mut offset = 0;
while offset < size { while offset < size {
let block: Block = bytes[offset..].into(); let block: Block =
bytes[offset..]
.try_into()
.map_err(|err| SSVMemoryError::BlockParsing {
source: err,
offset,
})?;
offset += block.size; offset += block.size;
blocks.push(block); blocks.push(block);
} }
blocks Ok(blocks)
} }
#[cfg(test)] #[cfg(test)]
mod test_element_size { mod test_element_size {
use std::any::Any;
use super::*; use super::*;
#[test] #[test]
@ -142,29 +195,51 @@ mod test_element_size {
#[test] #[test]
fn null_size() { fn null_size() {
let bytes: &[u8] = &[]; let bytes: &[u8] = &[];
let result: Result<ElementSize, &str> = bytes.try_into(); let result: Result<ElementSize, BytesReadingError> = bytes.try_into();
assert_eq!(result, Err("Empty bytes input"),); assert!(result.is_err());
assert_eq!(
result.unwrap_err().type_id(),
BytesReadingError::EmptyBytes.type_id()
);
} }
#[test] #[test]
fn invalid_memory() { fn invalid_memory() {
let bytes: &[u8] = &[0b_1000_0001_u8]; let bytes: &[u8] = &[0b_1000_0001_u8];
let result: Result<ElementSize, &str> = bytes.try_into(); let result: Result<ElementSize, BytesReadingError> = bytes.try_into();
assert!(result.is_err());
assert_eq!( assert_eq!(
result, result.unwrap_err().to_string(),
Err("Invalid memory: not enough bytes to read the size"), BytesReadingError::InvalidSize {
expected: 1,
actual: 0
}
.to_string()
); );
let bytes: &[u8] = &[0b_1000_0010_u8, 1]; let bytes: &[u8] = &[0b_1000_0010_u8, 1];
let result: Result<ElementSize, &str> = bytes.try_into(); let result: Result<ElementSize, BytesReadingError> = bytes.try_into();
assert!(result.is_err());
assert_eq!( assert_eq!(
result, result.unwrap_err().to_string(),
Err("Invalid memory: not enough bytes to read the size"), BytesReadingError::InvalidSize {
expected: 2,
actual: 1
}
.to_string()
); );
let bytes: &[u8] = &[0b_1000_0101_u8, 1, 1, 1, 1, 1]; let bytes: &[u8] = &[0b_1000_0101_u8, 1, 1, 1, 1, 1];
let result: Result<ElementSize, &str> = bytes.try_into(); let result: Result<ElementSize, BytesReadingError> = bytes.try_into();
assert_eq!(result, Err("Invalid memory: size is too big"),); assert!(result.is_err());
assert_eq!(
result.unwrap_err().to_string(),
BytesReadingError::SizeTooBig {
expected: 4,
actual: 5
}
.to_string()
);
} }
} }
@ -179,7 +254,7 @@ mod test_field {
80, 72, 65, 82, 77, 65, 67, 73, 69, 78, 48, 48, 53, 50, 52, 49, 57, 9, 70, 82, 65, 78, 80, 72, 65, 82, 77, 65, 67, 73, 69, 78, 48, 48, 53, 50, 52, 49, 57, 9, 70, 82, 65, 78,
67, 79, 73, 83, 69, 1, 84, 67, 79, 73, 83, 69, 1, 84,
]; ];
let element: Field = bytes.into(); let element: Field = bytes.try_into().unwrap();
assert_eq!(element.size, 52); assert_eq!(element.size, 52);
assert_eq!(element.content[..5], [1, 48, 1, 56, 11]); assert_eq!(element.content[..5], [1, 48, 1, 56, 11]);
} }
@ -194,7 +269,7 @@ mod test_field {
// Add 256 bytes to the content // Add 256 bytes to the content
bytes_vec.append(&mut vec![1; 256]); bytes_vec.append(&mut vec![1; 256]);
let bytes: &[u8] = &bytes_vec; let bytes: &[u8] = &bytes_vec;
let element: Field = bytes.into(); let element: Field = bytes.try_into().unwrap();
assert_eq!(element.size, 259); assert_eq!(element.size, 259);
assert_eq!(element.content.len(), 256); assert_eq!(element.content.len(), 256);
} }
@ -208,15 +283,15 @@ mod test_block {
fn test_francoise_pharmacien0052419_partial_block_1() { fn test_francoise_pharmacien0052419_partial_block_1() {
let bytes: &[u8] = &[1, 48, 1, 56, 11, 57, 57, 55, 48, 48, 53, 50, 52, 49, 57, 52]; let bytes: &[u8] = &[1, 48, 1, 56, 11, 57, 57, 55, 48, 48, 53, 50, 52, 49, 57, 52];
let field1: Field = bytes.into(); let field1: Field = bytes.try_into().unwrap();
assert_eq!(field1.size, 2); assert_eq!(field1.size, 2);
assert_eq!(field1.content, &[48]); assert_eq!(field1.content, &[48]);
let field2: Field = bytes[field1.size..].into(); let field2: Field = bytes[field1.size..].try_into().unwrap();
assert_eq!(field2.size, 2); assert_eq!(field2.size, 2);
assert_eq!(field2.content, &[56]); assert_eq!(field2.content, &[56]);
let field3: Field = bytes[field1.size + field2.size..].into(); let field3: Field = bytes[field1.size + field2.size..].try_into().unwrap();
assert_eq!(field3.size, 12); assert_eq!(field3.size, 12);
assert_eq!( assert_eq!(
field3.content, field3.content,
@ -243,12 +318,12 @@ mod test_block {
48, 2, 49, 48, 2, 48, 48, 1, 48, 1, 48, 1, 48, 1, 49, 1, 49, 48, 2, 49, 48, 2, 48, 48, 1, 48, 1, 48, 1, 48, 1, 49, 1, 49,
]; ];
let first_block: Block = bytes.into(); let first_block: Block = bytes.try_into().unwrap();
assert_eq!(first_block.id, 1); assert_eq!(first_block.id, 1);
assert_eq!(first_block.size, 54); assert_eq!(first_block.size, 54);
assert_eq!(first_block.content.len(), 8); assert_eq!(first_block.content.len(), 8);
let second_block: Block = bytes[first_block.size..].into(); let second_block: Block = bytes[first_block.size..].try_into().unwrap();
assert_eq!(second_block.id, 2); assert_eq!(second_block.id, 2);
assert_eq!(second_block.size, 86); assert_eq!(second_block.size, 86);
assert_eq!(second_block.content.len(), 21); assert_eq!(second_block.content.len(), 21);
@ -277,7 +352,7 @@ mod test_decode_ssv_memory {
50, 50, 49, 57, 53, 8, 48, 48, 50, 48, 50, 52, 49, 57, 1, 56, 0, 1, 48, 1, 49, 2, 53, 50, 50, 49, 57, 53, 8, 48, 48, 50, 48, 50, 52, 49, 57, 1, 56, 0, 1, 48, 1, 49, 2, 53,
48, 2, 49, 48, 2, 48, 48, 1, 48, 1, 48, 1, 48, 1, 49, 1, 49, 48, 2, 49, 48, 2, 48, 48, 1, 48, 1, 48, 1, 48, 1, 49, 1, 49,
]; ];
let blocks = decode_ssv_memory(bytes, bytes.len()); let blocks = decode_ssv_memory(bytes, bytes.len()).unwrap();
assert_eq!(blocks.len(), 2); assert_eq!(blocks.len(), 2);
} }
} }

View File

@ -6,25 +6,49 @@ use std::env;
use std::ffi::CString; use std::ffi::CString;
use std::path::PathBuf; use std::path::PathBuf;
use std::ptr; use std::ptr;
use thiserror::Error;
use crate::cps::lire_carte; use crate::cps::lire_carte;
use crate::libssv::{SSV_InitLIB2, SSV_LireConfig}; use crate::libssv::{SSV_InitLIB2, SSV_LireConfig};
fn ssv_init_lib_2() { #[derive(Error, Debug)]
pub enum SSVDemoError {
#[error(transparent)]
CartePSReading(#[from] crate::cps::CartePSError),
#[error(transparent)]
SSVLibErrorCode(#[from] crate::libssv::LibSSVError),
}
fn ssv_init_lib_2() -> Result<(), SSVDemoError> {
let ini_str = env::var("SESAM_INI_PATH").expect("SESAM_INI_PATH must be set"); let ini_str = env::var("SESAM_INI_PATH").expect("SESAM_INI_PATH must be set");
let ini = CString::new(ini_str).expect("CString::new failed"); let ini = CString::new(ini_str).expect("CString::new failed");
unsafe { unsafe {
let result = SSV_InitLIB2(ini.as_ptr()); let result = SSV_InitLIB2(ini.as_ptr());
println!("SSV_InitLIB2 result: {}", result); println!("SSV_InitLIB2 result: {}", result);
if result != 0 {
return Err(crate::libssv::LibSSVError::StandardErrorCode {
code: result,
function: "SSV_InitLIB2",
}
.into());
}
} }
Ok(())
} }
fn ssv_lire_config() { fn ssv_lire_config() -> Result<(), SSVDemoError> {
let mut buffer: *mut c_void = ptr::null_mut(); let mut buffer: *mut c_void = ptr::null_mut();
let mut size: size_t = 0; let mut size: size_t = 0;
unsafe { unsafe {
let result = SSV_LireConfig(&mut buffer, &mut size); let result = SSV_LireConfig(&mut buffer, &mut size);
println!("SSV_LireConfig result: {}", result); println!("SSV_LireConfig result: {}", result);
if result != 0 {
return Err(crate::libssv::LibSSVError::StandardErrorCode {
code: result,
function: "SSV_LireConfig",
}
.into());
}
if !buffer.is_null() { if !buffer.is_null() {
let hex_values = std::slice::from_raw_parts(buffer as *const u8, size); let hex_values = std::slice::from_raw_parts(buffer as *const u8, size);
@ -36,25 +60,27 @@ fn ssv_lire_config() {
libc::free(buffer); libc::free(buffer);
} }
} }
Ok(())
} }
pub fn demo() { pub fn demo() -> Result<(), SSVDemoError> {
// TODO : this is probably not working on release, because I'm not sure it exists a CARGO_MANIFEST_DIR and so it can find the `.env` // TODO : this is probably not working on release, because I'm not sure it exists a CARGO_MANIFEST_DIR and so it can find the `.env`
// Maybe we could use a system standard config path to store a config file // Maybe we could use a system standard config path to store a config file
let manifest_dir = env::var("CARGO_MANIFEST_DIR").unwrap(); let manifest_dir = env::var("CARGO_MANIFEST_DIR").expect("CARGO_MANIFEST_DIR must be set");
let manifest_path = PathBuf::from(manifest_dir); let manifest_path = PathBuf::from(manifest_dir);
dotenv::from_path(manifest_path.join(".env")).ok(); dotenv::from_path(manifest_path.join(".env")).ok();
println!("------- Demo for the SSV library --------"); println!("------- Demo for the SSV library --------");
ssv_init_lib_2(); ssv_init_lib_2()?;
let code_pin = "1234"; let code_pin = "1234";
let lecteur = "HID Global OMNIKEY 3x21 Smart Card Reader 0"; let lecteur = "HID Global OMNIKEY 3x21 Smart Card Reader 0";
let carte_ps = lire_carte(code_pin, lecteur).unwrap(); let carte_ps = lire_carte(code_pin, lecteur)?;
println!("CartePS: {:#?}", carte_ps); println!("CartePS: {:#?}", carte_ps);
ssv_lire_config(); ssv_lire_config()?;
println!("-----------------------------------------"); println!("-----------------------------------------");
Ok(())
} }

85
docs/errors.md Normal file
View File

@ -0,0 +1,85 @@
# Gestion des erreurs
Ce document décrit comment les erreurs sont gérées dans le projet.
## Gestion native
Par principe, en Rust, on évite au maximum la gestion par exception, ne la réservant qu'aux situations où un crash du programme est la meilleure solution.
En temps normal, on renvoie des `Result<Valeur, Erreur>` (pour les situations réussite/erreur) ou des `Option<Valeur>` (pour les situations valeur non-nulle/nulle).
Quand on fait face à une situation d'erreur, on cherchera à la gérer de manière explicite (voir [Récupération des erreurs](#récupération-des-erreurs)) ou à la remonter à un niveau supérieur, généralement à l'aide de l'opérateur `?`.
On évitera, par contre, au maximum de générer des exceptions (appelées "panics" en Rust), que ce soit par l'usage de `panic!` ou par des appels à des fonctions qui paniquent en cas d'erreur (comme `unwrap` ou `expect`).
De nombreux exemples des idiomes natifs de gestion des erreurs en Rust sont disponibles dans la documentation [Rust by example](https://doc.rust-lang.org/rust-by-example/error.html).
## Librairies de gestion des erreurs
Deux librairies sont utilisées pour gérer les erreurs dans le projet :
- [`anyhow`](https://docs.rs/anyhow/latest/anyhow/) : qui permet de renvoyer des erreurs faiblement typées, mais très facile à enrichir avec des messages d'explication. On l'utilise pour communiquer facilement des erreurs de haut niveau avec un utilisateur final.
```rust
use anyhow::{anyhow, Result};
fn get_cluster_info() -> Result<ClusterInfo> {
let data = fs::read_to_string("cluster.json")
.with_context(|| "failed to read cluster config")?;
let info: ClusterInfo = serde_json::from_str(&data)
.with_context(|| "failed to parse cluster config")?;
Ok(info)
}
```
- [`thiserror`](https://docs.rs/thiserror/latest/thiserror/) : qui fournit des macros pour définir des erreurs fortement typées. On l'utilise pour définir des erreurs spécifiques à une partie du code, contextualisées avec des données structurées plutôt que de simples messages d'erreurs, afin de favoriser la "récupération" face aux erreurs.
```rust
use thiserror::Error;
#[derive(Error, Debug)]
pub enum DataStoreError {
#[error("data store disconnected")]
Disconnect(#[from] io::Error),
#[error("the data for key `{0}` is not available")]
Redaction(String),
#[error("invalid header (expected {expected:?}, found {found:?})")]
InvalidHeader {
expected: String,
found: String,
},
#[error("unknown data store error")]
Unknown,
}
```
## Récupération des erreurs
Dans la mesure du possible, on essaie de privilégier la "récupération" face à une erreur plutôt que le "crash". Les stratégies de récupération sont :
- Réessayer l'opération, tel quel ou avec des paramètres différents
- Contourner l'opération, en la remplaçant par une autre
- À défaut, informer l'utilisateur de l'erreur et :
- arrêter / annuler l'opération en cours
- ignorer l'erreur et continuer l'exécution
Quand on ne peut pas récupérer une erreur, on la remonte à un niveau supérieur, si besoin en la convertissant dans un type d'erreur plus générique et approprié au niveau considéré.
## Conversion des erreurs
Quand on remonte une erreur à un niveau supérieur, on peut être amené à la convertir dans un type d'erreur plus générique et approprié au niveau considéré. Pour faciliter cette conversion, on implémente le trait `From`. Avec `thiserror`, on peut utiliser l'attribut `#[from]` ou le paramètre `source` pour automatiser l'implémentation de telles conversions.
On peut ensuite, lors de la gestion d'une erreur, on pourra :
- soit directement renvoyer l'erreur à l'aide de l'opérateur `?`, qui se chargera de la conversion ;
- soit convertir l'erreur explicitement, par exemple en utilisant la méthode `map_err` sur un `Result`, en particulier quand on veut enrichir l'erreur avec des informations supplémentaires.
## Usages exceptionnels de `unwrap` et `expect`
Provoquant des "panics" en cas d'erreur, les fonctions `unwrap` et `expect` ne doivent être utilisées que dans des cas exceptionnels :
- Dans les tests, pour signaler une erreur de test
- Au plus haut niveau de l'application, pour signaler une erreur fatale qui ne peut pas être récupérée
- Dans des situations où l'erreur ne peut pas se produire, par exemple après une vérification de préconditions
Dans l'idéal, on préférera l'usage de `expect` à `unwrap`, car il permet de donner un message d'erreur explicite.
## Ressources
- [The Rust Programming Language - Ch. 9: Error Handling](https://doc.rust-lang.org/book/ch09-00-error-handling.html)
- [The NRC Book - Error Handling in Rust](https://nrc.github.io/error-docs/intro.html)
- [The Error Design Patterns Book - by Project Error Handling WG](https://github.com/rust-lang/project-error-handling/blob/master/error-design-patterns-book/src/SUMMARY.md)
- [The Rust Cookbook - Error Handling](https://rust-lang-nursery.github.io/rust-cookbook/error-handling.html)
- [Le ticket initial de l'intégration de la gestion des erreurs dans le projet](https://forge.p4pillon.org/P4Pillon/Krys4lide/issues/34)