Build tools should be in dependencies, not devDependencies

Problem

Currently, Shakapacker's package.json has build tooling (webpack, rspack, loaders, plugins) in devDependencies instead of dependencies. This creates several issues:

1. Production Builds May Fail

When Shakapacker is installed in a production environment or during deployment:

• npm install --production skips devDependencies
• Build tools like webpack, rspack, swc-loader, babel-loader, etc. are not installed in Shakapacker's node_modules
• If the consuming application relies on Shakapacker's bundled tools (via resolveLoader or similar), the build will fail

2. Inconsistent Behavior Between Environments

• Development (with npm install): Build tools are present in node_modules
• Production (with npm install --production): Build tools are missing
• CI/CD: Behavior depends on whether NODE_ENV=production is set

3. File Path Dependencies Issue

When using Shakapacker via a local file path (e.g., during development with "shakapacker": "file:../shakapacker"):

• Webpack's resolveLoader can find loaders like swc-loader in Shakapacker's node_modules (because devDependencies are installed)
• But those loaders may fail to find their own dependencies (like @swc/core) because peer dependencies don't get installed in nested node_modules
• This led to the workaround of adding @swc/core to devDependencies (commit 2015f79)

Current State

{
  "dependencies": {
    "js-yaml": "^4.1.0",
    "path-complete-extname": "^1.0.0",
    "webpack-merge": "^5.8.0"
  },
  "devDependencies": {
    "@rspack/cli": "^1.4.11",
    "@rspack/core": "^1.4.11",
    "@swc/core": "^1.3.0",
    "babel-loader": "^8.2.4",
    "compression-webpack-plugin": "^9.0.0",
    "css-loader": "^7.1.2",
    "esbuild-loader": "^2.18.0",
    "mini-css-extract-plugin": "^2.9.4",
    "rspack-manifest-plugin": "^5.0.3",
    "sass-loader": "^16.0.5",
    "swc-loader": "^0.1.15",
    "webpack": "5.93.0",
    "webpack-assets-manifest": "^5.0.6",
    "webpack-subresource-integrity": "^5.1.0",
    // ... plus ESLint, TypeScript, Jest, etc.
  },
  "peerDependencies": {
    // Same build tools listed here (correct)
  }
}

Proposed Solution

Move runtime build tools from devDependencies to dependencies:

Should be in dependencies:

• All bundler cores: webpack, @rspack/core, @rspack/cli
• All loaders: babel-loader, swc-loader, esbuild-loader, css-loader, sass-loader
• All plugins: mini-css-extract-plugin, compression-webpack-plugin, webpack-assets-manifest, rspack-manifest-plugin, webpack-subresource-integrity
• Loader peer deps that are commonly resolved from Shakapacker's node_modules: @swc/core (added in 2015f79)

Should remain in devDependencies:

• TypeScript compiler and type definitions: typescript, @types/*
• Linting and formatting: eslint, prettier, eslint-*
• Testing: jest, @jest/*
• Development tooling: husky, lint-staged

Should remain in peerDependencies:

• All build tools (so consuming apps know they need to install them)
• Keep all as optional: true in peerDependenciesMeta

Impact

Breaking Change?

This could be considered a breaking change if:

• Some users are relying on npm install --production NOT installing build tools
• Bundle size increases for published package

However, this is more of a bug fix because:

• The current setup breaks production builds in certain configurations
• It creates inconsistent behavior between development and production
• The peerDependencies already declare these as requirements

Migration Path

1. Move packages from devDependencies to dependencies
2. Update documentation to explain that build tools are bundled
3. Consider if this should be a major version bump (10.0.0) or a minor/patch

Related Issues

• Caused the @swc/core resolution issue that required commit 2015f79
• May explain issues users have reported with production builds
• Related to the general peer dependency resolution strategy

References

• Commit 2015f79: "Add @swc/core to devDependencies" (workaround for this issue)
• Similar discussion in other build tool integrations (Vite, etc.)