EagerEye for VS Code

Catch N+1 queries in your Rails app — on save, right in your editor.

Catch N+1 queries before they hit production — right in your editor.

Table of Contents

• Features
• Installation
• Quick Start
• Detected Issues
• Commands
• Extension Settings
• Extension vs CLI
• Troubleshooting
• How It Works
• Related
• License

Features

On-save Analysis — Runs automatically every time you save a Ruby file. No build step, no test suite needed.

Problem Highlighting — Squiggly underlines show exactly where N+1 queries may occur. Hover for details and suggestions.

Quick Fixes — One-click fixes for common issues (.pluck(:id) → .select(:id), etc.) and inline # eager_eye:disable toggles.

Status Bar Integration — Issue count at a glance, click to jump to the Problems panel.

11 Detector Types — Comprehensive detection covering the most common N+1 patterns in Rails applications.

Installation

Prerequisites

Install the EagerEye gem:

gem install eager_eye

Or add to your Gemfile:

gem "eager_eye", group: :development

Install Extension

Option 1: Search for "EagerEye" in VS Code Extensions (Cmd+Shift+X / Ctrl+Shift+X)

Option 2: Install from VS Code Marketplace

Option 3: Command line:

code --install-extension hamzagedikkaya.eager-eye

Quick Start

1. Open a Rails project in VS Code
2. Open any Ruby file (controller, model, serializer, etc.)
3. Save the file — EagerEye automatically analyzes it
4. Issues appear as warnings with squiggly underlines
5. Hover over underlined code to see details and suggestions

Detected Issues

EagerEye detects 11 types of N+1 query patterns:

Quick Fixes

• Auto-fix generic N+1 queries where possible.
• Pluck to Select: Safely converts .pluck(:id) to .select(:id) inside where clauses.
  • Smart Safety: Only fixes safe patterns and ignores small collections (Info severity).

Severity Levels

• Error: Critical N+1 queries (e.g. .all.pluck).
• Warning: Standard N+1 queries.
• Info: Low impact issues or small collections.

Example Detection

# EagerEye will warn about this:
posts.each do |post|
  post.author.name      # ⚠️ N+1 query detected
  post.comments.count   # ⚠️ COUNT query for each post
end

# Suggested fix:
posts.includes(:author, :comments).each do |post|
  post.author.name      # ✓ No additional query
  post.comments.size    # ✓ No additional query
end

Commands

Access commands via Command Palette (Cmd+Shift+P / Ctrl+Shift+P):

Extension Settings

Configure EagerEye in VS Code settings (Cmd+, / Ctrl+,):

Example Configuration

{
  "eagerEye.enable": true,
  "eagerEye.analyzeOnSave": true,
  "eagerEye.excludePatterns": [
    "**/spec/**",
    "**/test/**",
    "**/vendor/**",
    "**/legacy/**"
  ],
  "eagerEye.enabledDetectors": [
    "loop_association",
    "serializer_nesting"
  ]
}

Extension vs CLI

Both this extension and the EagerEye gem use the same analysis engine. Use whichever fits the moment:

A typical workflow uses both: extension during development, CLI in CI to gate PRs.

Troubleshooting

gem install eager_eye
which eager_eye   # should print a path

{
  "eagerEye.gemPath": "/Users/you/.rbenv/shims/eager_eye"
}

cd path/to/your/project
gem install eager_eye   # installs for the project's Ruby

{
  "eagerEye.gemPath": "bundle exec eager_eye"
}

user.posts.count  # eager_eye:disable CountInIteration

{
  "eagerEye.excludePatterns": [
    "**/spec/**", "**/test/**", "**/vendor/**", "**/db/migrate/**"
  ]
}

How It Works

EagerEye uses static analysis with AST (Abstract Syntax Tree) parsing to detect N+1 query patterns without running your code. This means:

• No test suite required — works on any Ruby file
• No runtime overhead — analysis happens at parse time
• Fast feedback — runs on every save

For maximum coverage pair it with Bullet — static analysis catches code paths your tests don't hit, runtime analysis catches what static can't see.

Compatibility

The extension automatically picks up new detector types added to the gem — no extension update needed.

Related

• 📦 EagerEye Gem — analysis engine + CLI
• 💎 RubyGems — gem installation
• 📋 CHANGELOG — release notes
• 🐛 Report a bug
• 💬 Ask a question

License

MIT — see LICENSE.

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