Code quality improvements: Extract constants, simplify validation, optimize Rails generators

[justin808]

Context

From PR #13 code review - nice-to-have code quality improvements.

Improvements

1. Simplify Validation Logic (demo_creator.rb:95-102)

Current: Multiple conditional checks make method longer.

Current code:

def validate_demo_name!(name)
  raise ArgumentError, 'Demo name cannot be empty' if name.nil? || name.strip.empty?
  raise ArgumentError, 'Demo name cannot contain slashes' if name.include?('/')
  raise ArgumentError, 'Demo name cannot start with . or _' if name.start_with?('.', '_')
  return if name.match?(/^[a-zA-Z0-9_-]+$/)
  raise ArgumentError, 'Demo name can only contain alphanumeric characters, hyphens, and underscores'
end

Suggested improvement:

def validate_demo_name!(name)
  # Valid: not empty, no slashes, doesn't start with . or _, only alphanumeric/hyphens/underscores
  unless name =~ /\A(?![._])[a-zA-Z0-9_-]+\z/ && !name.strip.empty?
    raise ArgumentError, 
          'Demo name must be non-empty, not start with . or _, and only contain ' \
          'alphanumeric characters, hyphens, and underscores'
  end
end

Note: Consider keeping current approach for better error messages. Single regex is more compact but less user-friendly.

2. Extract Duplicate Prerelease Logic (demo_creator.rb:501-502)

Current: Logic duplicated for determining prerelease status.

Current code:

'shakapacker_prerelease' => @config.shakapacker_version&.start_with?('github:'),
'react_on_rails_prerelease' => @config.react_on_rails_version&.start_with?('github:')

Suggested improvement:

def prerelease_version?(version)
  version&.start_with?('github:')
end

# In metadata:
'shakapacker_prerelease' => prerelease_version?(@config.shakapacker_version),
'react_on_rails_prerelease' => prerelease_version?(@config.react_on_rails_version)

3. Simplify .gitignore Conditional (install_generator.rb)

Current: Conditional logic for handling .gitignore could be simplified.

Current code:

if File.exist?('.gitignore')
  append_to_file '.gitignore', gitignore_content
else
  create_file '.gitignore', gitignore_content
end

Rails generators already handle this: append_to_file will create the file if it doesn't exist.

Suggested improvement:

append_to_file '.gitignore', gitignore_content

4. Extract Magic Numbers to Constants

Current locations:

• e2e_test_runner.rb:84-86 - Server startup constants
• e2e_test_runner.rb:54-55 - Port release delay

Recommendation: These are already extracted. No action needed unless adding more magic numbers.

Additional Considerations

Method Length

Some methods are long but readable. Consider:

• Extract methods only if it improves clarity
• Keep cohesive logic together
• Prioritize readability over strict line counts

Comments in Playwright Config

Consider adding comments to playwright.config.ts explaining:

• Why certain timeouts are set
• What the base URL should be
• Browser configuration rationale

Acceptance Criteria

• Decide on validation approach (clarity vs compactness)
• Extract prerelease_version? helper if valuable
• Simplify .gitignore handling
• Add comments to Playwright config
• All tests still pass
• No breaking changes