Add draft comment for package_json gem issue #25

This comment explains React on Rails' use case for exact version support
and provides context for why we had to implement a workaround.

To be posted at: shakacode/package_json#25

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: justin808

package_json_issue_comment.md

@@ -0,0 +1,58 @@
+## React on Rails Use Case
+
+We encountered this limitation in React on Rails and had to work around it by bypassing the `package_json` gem for our main package installation.
+
+### Context
+
+React on Rails requires **exact version matching** between the Ruby gem and npm package (e.g., gem version `16.1.1` must match npm package version `16.1.1` exactly, not `^16.1.1`). This is because the gem and package have tightly coupled APIs that must stay in sync.
+
+### Problem
+
+When using `package_json.manager.add(["react-on-rails@16.1.1"])`, the package gets installed with a caret (`^16.1.1`), which our version checker then rejects during Rails initialization.
+
+This was causing our generator tests to fail because:
+
+1. Generator runs `package_json.manager.add(["react-on-rails@16.1.1"])`
+2. Package gets added to package.json as `"react-on-rails": "^16.1.1"`
+3. Our version checker validates that versions match exactly
+4. Validation fails with error about non-exact version
+
+### Current Workaround
+
+We had to bypass the gem and use direct npm commands:
+
+```ruby
+# lib/generators/react_on_rails/install_generator.rb
+def add_react_on_rails_package
+  # Always use direct npm install with --save-exact to ensure exact version matching
+  # The package_json gem doesn't support --save-exact flag
+  react_on_rails_pkg = "react-on-rails@#{ReactOnRails::VERSION}"
+
+  puts "Installing React on Rails package..."
+  success = system("npm", "install", "--save-exact", react_on_rails_pkg)
+  # ...
+end
+```
+
+### Why We Need This Feature
+
+1. **The gem's abstraction is valuable** - We'd prefer to use the package_json gem's API rather than maintaining package-manager-specific command strings
+2. **Loss of package manager agnosticism** - Having to use direct npm commands defeats the purpose of the gem, as we can no longer support yarn/pnpm/bun automatically
+3. **Exact version pinning is a legitimate use case** - Packages with tightly coupled Ruby gem + npm package pairs need this feature
+
+### Proposed API
+
+Would love to see something like:
+
+```ruby
+package_json.manager.add(["react-on-rails@16.1.1"], exact: true)
+```
+
+This would translate to:
+
+- **npm/pnpm**: `--save-exact`
+- **yarn/bun**: `--exact`
+
+Happy to test this feature in React on Rails once it's available!
+
+**Reference**: shakacode/react_on_rails@f2a0e331