Migrate spec/dummy to use SWC transpiler

[justin808]

Summary

The spec/dummy test application currently uses Babel as the JavaScript transpiler (Shakapacker 8.2.0 default). With Shakapacker 9.3.0+, SWC is the default transpiler and is ~20x faster than Babel.

Current State

• spec/dummy/package.json: Uses Babel dependencies (@babel/core, babel-loader, etc.)
• spec/dummy/config/shakapacker.yml: No javascript_transpiler setting (defaults to Babel)
• Shakapacker version: 8.2.0

Proposed Changes

1. Update spec/dummy/config/shakapacker.yml to add:

   default: &default
     javascript_transpiler: swc

2. Add SWC dependencies to spec/dummy/package.json:

   "devDependencies": {
     "@swc/core": "^1.7.0",
     "swc-loader": "^0.2.6"
   }

3. Optionally upgrade Shakapacker to 9.3.0+ to get the default SWC behavior

4. Verify all tests pass with the new configuration

Benefits

• Faster webpack builds during test runs
• Better alignment with recommended Shakapacker 9.3.0+ defaults
• Tests will exercise the SWC code path

Testing Checklist

• rake run_rspec:dummy passes
• yarn build:test completes successfully
• Hot reloading works in development mode
• All integration tests pass

Related

This issue was created as a follow-up to the SWC detection feature PR to keep changes focused.

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🔗 Similar Issues

Possible Duplicates

• shakacode/react-webpack-rails-tutorial#666

Related Issues

• shakacode/shakapacker#628
• shakacode/react-webpack-rails-tutorial#678
• shakacode/shakapacker#634
• shakacode/shakapacker#656
• shakacode/react_on_rails#1956
• shakacode/react-webpack-rails-tutorial#668

🔗 Related PRs

shakacode/shakapacker#603 - Make babel dependencies optional instead of peer dependencies [merged]
shakacode/react-webpack-rails-tutorial#669 - Fix ReScript deprecation warnings [merged]
shakacode/react-webpack-rails-tutorial#677 - Switch from Babel to SWC for faster JavaScript transpilation [merged]
shakacode/shakapacker#803 - Update docs to clarify SWC is the default JavaScript transpiler [merged]
#1904 - Upgrade Shakapacker from 8.2.0 to 9.0.0 [merged]
#1932 - Migrate from Babel to SWC for faster JavaScript transpilation [merged]

👤 Suggested Assignees

• justin808

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[justin808]

Closing this issue - it was created in error. Master already has spec/dummy configured to use SWC (javascript_transpiler: swc in shakapacker.yml). The actual issue is that master is missing the SWC npm dependencies (@swc/core, swc-loader) in package.json, which should be added separately.