Coding Standards

Coding Standards

Language Rules

Comments and Documentation

All comments, documentation, and error messages must be in Japanese

// ✅ Correct
/// ユーザーを作成する
pub async fn create_user() -> Result<()> {
    // ユーザー情報をバリデーション
}

// ❌ Wrong
/// Create a user
pub async fn create_user() -> Result<()> {
    // Validate user info
}

Naming Conventions

• Structs/Enums/Type Aliases: PascalCase
• Functions/Methods/Variables: snake_case
• Constants: SCREAMING_SNAKE_CASE

// ✅ Correct
struct UserData { }
const MAX_RETRIES: u32 = 3;
fn create_user() { }

// ❌ Wrong
struct user_data { }
const maxRetries: u32 = 3;
fn CreateUser() { }

Error Handling

Using thiserror

Define appropriate error types per layer

use thiserror::Error;

#[derive(Error, Debug)]
pub enum ServiceError {
    #[error("ユーザーが見つかりません: {0}")]
    UserNotFound(String),

    #[error("バリデーションエラー: {0}")]
    ValidationError(String),

    #[error("データベースエラー")]
    DatabaseError(#[from] DbErr),
}

Error Conversion

Use #[from] attribute for cross-layer error conversion

#[derive(Error, Debug)]
pub enum FacadeError {
    #[error("サービスエラー")]
    ServiceError(#[from] ServiceError),

    #[error("リポジトリエラー")]
    RepositoryError(#[from] RepositoryError),
}

Prohibited

• Prohibited: unwrap() in production code
• panic!() only for unrecoverable situations

// ❌ Prohibited
let user = find_user().unwrap();

// ✅ Correct
let user = find_user().map_err(|e| ServiceError::UserNotFound(e.to_string()))?;

Logging

Using tracing

Use structured logging

use tracing::{error, warn, info, debug};

// ERROR: System errors, unexpected exceptions
error!(error = %e, user_id = %user_id, "ユーザー作成に失敗しました");

// WARN: Business exceptions, retryable errors
warn!(recruitment_id = %id, "募集が満員のため参加を拒否しました");

// INFO: Important business operations start/end
info!(quest_name = %quest_name, "募集作成を開始しました");

// DEBUG: Debug information
debug!(params = ?params, "リクエストパラメータ");

文字列フォーマット（format!マクロ）

• 禁止: format!("{}", a) のような書き方は避けること
• 推奨: 変数埋め込み format!("{a}") を使うこと
• 備考: この規約を守らないと cargo clippy による警告が発生します

// ❌ 禁止
let s = format!("{}", user_name);

// ✅ 推奨
let s = format!("{user_name}");

Log Levels

Performance

Ownership and Borrowing

Avoid unnecessary clone(), use borrowing

// ❌ Avoid
fn process(data: String) {
    let copied = data.clone();
    // ...
}

// ✅ Recommended
fn process(data: &str) {
    // ...
}

Arc Usage

Minimize Arc<T> usage

// ❌ Avoid (unnecessary Arc)
fn process(data: Arc<String>) {
    // ...
}

// ✅ Recommended (borrowing is enough)
fn process(data: &str) {
    // ...
}

Code Quality

Function Length

• Prohibited: Functions over 100 lines
• Prohibited: Nesting deeper than 5 levels

// ❌ Avoid
fn complex_function() {
    if condition1 {
        if condition2 {
            if condition3 {
                if condition4 {
                    if condition5 {
                        // Too deep
                    }
                }
            }
        }
    }
}

// ✅ Recommended (early return)
fn simple_function() -> Result<()> {
    if !condition1 { return Ok(()); }
    if !condition2 { return Ok(()); }
    if !condition3 { return Ok(()); }
    // Flat structure
    Ok(())
}

Concurrency

Use futures for concurrent operations

use futures::future::try_join_all;

// ✅ Concurrent processing
let futures = items.iter().map(|item| process_item(item));
let results = try_join_all(futures).await?;

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