Rails Upgrade Assistant Skill v1.0

How It Works

Three-step process:

1. Detection Script — Generate a bash script that scans the codebase for breaking changes with file:line references
2. User Runs Script — User executes it, gets rails_{version}_upgrade_findings.txt
3. Reports — Generate upgrade report and app:update preview based on actual findings (not hypothetical)

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Sequential Upgrade Strategy

⚠️ Version Skipping is NOT Allowed

Rails upgrades MUST follow this exact sequence:

7.0.x → 7.1.x → 7.2.x → 8.0.x → 8.1.x

You CANNOT skip versions. Examples:

• ❌ 7.0 → 7.2 (skips 7.1)
• ❌ 7.0 → 8.0 (skips 7.1 and 7.2)
• ✅ 7.0 → 7.1 (correct)
• ✅ 7.1 → 7.2 (correct)

If user requests a multi-hop upgrade (e.g., 7.0 → 8.1):

1. Explain the sequential requirement
2. Break it into individual hops
3. Generate separate reports for each hop
4. Recommend completing each hop fully before moving to next

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Available Resources

Core Documentation

• docs/README.md - Human-readable overview
• docs/QUICK-REFERENCE.md - Command cheat sheet
• docs/USAGE-GUIDE.md - Comprehensive how-to

Version-Specific Guides (Load as needed)

• version-guides/upgrade-7.0-to-7.1.md - Rails 7.0 → 7.1
• version-guides/upgrade-7.1-to-7.2.md - Rails 7.1 → 7.2
• version-guides/upgrade-7.2-to-8.0.md - Rails 7.2 → 8.0
• version-guides/upgrade-8.0-to-8.1.md - Rails 8.0 → 8.1

Workflow Guides (Load when generating deliverables)

• workflows/upgrade-report-workflow.md - How to generate upgrade reports
• workflows/detection-script-workflow.md - How to generate detection scripts
• workflows/app-update-preview-workflow.md - How to generate app:update previews

Examples (Load when user needs clarification)

• examples/simple-upgrade.md - Single-hop upgrade example
• examples/multi-hop-upgrade.md - Multi-hop upgrade example
• examples/detection-script-only.md - Detection script only request
• examples/preview-only.md - Preview only request

Reference Materials

• reference/breaking-changes-by-version.md - Quick lookup
• reference/multi-hop-strategy.md - Multi-version planning
• reference/deprecations-timeline.md - Deprecation tracking
• reference/testing-checklist.md - Comprehensive testing
• reference/pattern-file-guide.md - How to use pattern files
• reference/quality-checklist.md - Pre-delivery verification
• reference/troubleshooting.md - Common issues and solutions

Detection Script Resources

• detection-scripts/patterns/rails-72-patterns.yml - Rails 7.2 patterns
• detection-scripts/patterns/rails-80-patterns.yml - Rails 8.0 patterns
• detection-scripts/patterns/rails-81-patterns.yml - Rails 8.1 patterns
• detection-scripts/templates/detection-script-template.sh - Bash template

Report Templates

• templates/upgrade-report-template.md - Main upgrade report structure
• templates/app-update-preview-template.md - Configuration preview

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Workflow

Phase 1: Generate Detection Script

1. Detect current Rails version from Gemfile.lock
2. Read detection-scripts/patterns/rails-{VERSION}-patterns.yml
3. Read detection-scripts/templates/detection-script-template.sh
4. Read workflows/detection-script-workflow.md
5. Generate version-specific bash script and deliver to user

Phase 2: User Runs Script

User runs the script, gets findings. Wait for them to share rails_{version}_upgrade_findings.txt.

Phase 3: Generate Reports

1. Parse findings.txt — extract breaking changes and affected files
2. Read version-guides/upgrade-{FROM}-to-{TO}.md
3. Read workflows/upgrade-report-workflow.md and workflows/app-update-preview-workflow.md
4. Generate Comprehensive Upgrade Report with real code from the user's project
5. Generate app:update Preview with actual config file diffs

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Quality

Before delivering any output, verify against reference/quality-checklist.md. Key rules:

• Replace all {PLACEHOLDERS} with actual values
• Use ACTUAL findings from the script, not generic examples
• Include real file:line references and real code from the user's project
• Flag custom code with warnings

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Bundled Resources

Load these as needed — don't read everything upfront:

Directory	When to load
workflows/	Before generating detection scripts or reports
version-guides/	When you need version-specific breaking changes
templates/	When generating report output
detection-scripts/patterns/	When building the detection script
examples/	When user needs clarification on the process
reference/	For quality checks, troubleshooting, pattern file format