"Asset was not declared to be precompiled in production" even though I'm in development mode

Question

This is the full error:

Asset was not declared to be precompiled in production.
Add `Rails.application.config.assets.precompile += %w( tutorial.js )` to `config/initializers/assets.rb` and restart your server

When the server starts up, it say that it's in development:

=> Booting Puma
=> Rails 5.1.7 application starting in development

Answer 1

Sometimes clearing the tmp can help. rake tmp:clear