I see no documentation on manifest.js and even doubt if its being used at all. I deleted its content and precompiled assets for production and it works just fine.
bundle exec rails assets:precompile RAILS_ENV=production
The manifest.js is required for Sprockets 4. Please see sprockets/UPGRADING.md for details.
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The
manifest.jsis required for Sprockets 4. Please see sprockets/UPGRADING.md for details.