Development Guidelines

Coding standards, naming conventions, and language conventions for PicoRuby development.

Output Style & Language

For complete output style requirements (Japanese output with ピョン。ending, etc.), see:

.claude/docs/output-style.md — PROTECTED output style requirements

Code Comments

Ruby files (.rb):

• Language: Japanese
• Style: Noun-ending (体言止め) — no period needed
• Purpose: Explain the why, not the what

# ピクセルの色計算
def calc_color(intensity)
  # 0-255 スケールで正規化
  # グリーンチャネル優先
  [0, intensity, intensity / 2]
end

Documentation Files

Markdown (.md):

• Language: English
• Purpose: Reference material, API docs, architecture
• No Japanese in .md files (except code comments within blocks)

Git Commits

Format: English, imperative mood

Add LED animation feature
Implement blinking pattern with configurable frequency.

Guidelines:

• Title: 50 chars max, imperative ("Add", "Fix", "Refactor")
• Body: Explain why the change matters (if needed)
• Always use commit subagent (never raw git commands)

Examples:

• ✅ "Add MP3 playback support"
• ✅ "Fix memory leak in LED buffer"
• ✅ "Refactor IMU data reading for clarity"
• ❌ "Added new feature"
• ❌ "Fixed stuff"

Test Temporary Files Management

Principle: Block-Based Temp File Creation

Reasons:

• Security: Prevent symlink attacks (IPA security guidelines)
• Safety: Guaranteed cleanup on block exit (even on exceptions)
• Reference: Rubyist Magazine 0029, "安全に一時ファイルを作成するのは素人には難しく"

Pattern A: File Operations (Preferred)

test "file operation" do
  Tempfile.open('test') do |file|
    file.write("content")
    # Assertions
  end  # Auto-deleted
end

Docs: https://docs.ruby-lang.org/ja/latest/class/Tempfile.html

Pattern B: Directory Structures (When Needed)

test "directory structure" do
  Dir.mktmpdir do |tmpdir|
    Dir.chdir(tmpdir) do
      FileUtils.mkdir_p("foo/bar")
      # Assertions
    end
  end  # Removed by FileUtils.remove_entry_secure
end

Docs: https://docs.ruby-lang.org/ja/latest/method/Dir/s/mktmpdir.html

Exception: setup/teardown (Discouraged)

• Use only when: Multiple tests must share state
• Must: Implement teardown for guaranteed cleanup (FileUtils.rm_rf)
• Risk: Cleanup failure if teardown not executed

References

• https://docs.ruby-lang.org/ja/latest/class/Tempfile.html
• https://docs.ruby-lang.org/ja/latest/method/Dir/s/mktmpdir.html
• https://magazine.rubyist.net/articles/0029/0029-BundledLibraries.html