Error deploying Rails 7 app to fly.io with Tailwind and Flowbite

This error had me stumped for a few hours the other night. I'm using fly.io to host a project that I'm working on to help manage in-home child care providers run their business.

 > [build 6/6] RUN SECRET_KEY_BASE=DUMMY ./bin/rails assets:precompile:                                             
#15 3.687                                                                                                           
#15 3.687 Rebuilding...                                                                                             
#15 3.734 Error: Cannot find module '@tailwindcss/forms'                                                            
#15 3.734 Require stack:
#15 3.734 - /rails/config/tailwind.config.js
#15 3.734     at Function.Module._resolveFilename (node:internal/modules/cjs/loader:933:15)
#15 3.734     at Function._resolveFilename (pkg/prelude/bootstrap.js:1955:46)
#15 3.734     at Function.resolve (node:internal/modules/cjs/helpers:108:19)
#15 3.734     at _resolve (/snapshot/tailwindcss/node_modules/jiti/dist/jiti.js:1:241025)
#15 3.734     at jiti (/snapshot/tailwindcss/node_modules/jiti/dist/jiti.js:1:243309)
#15 3.734     at /rails/config/tailwind.config.js:54:5
#15 3.734     at jiti (/snapshot/tailwindcss/node_modules/jiti/dist/jiti.js:1:245784)
#15 3.734     at /snapshot/tailwindcss/lib/lib/load-config.js:37:30
#15 3.734     at loadConfig (/snapshot/tailwindcss/lib/lib/load-config.js:39:6)
#15 3.734     at Object.loadConfig (/snapshot/tailwindcss/lib/cli/build/plugin.js:135:49) {
#15 3.734   code: 'MODULE_NOT_FOUND',
#15 3.734   requireStack: [ '/rails/config/tailwind.config.js' ]
#15 3.734 }
#15 3.744 rails aborted!
#15 3.744 Command failed with exit 1: /rails/vendor/bundle/ruby/3.2.0/gems/tailwindcss-rails-2.0.29-x86_64-linux/exe/x86_64-linux/tailwindcss
...<removed some unuseful stack trace here>...
#15 3.745 Tasks: TOP => assets:precompile => tailwindcss:build
#15 3.745 (See full trace by running task with --trace)
------
Error: failed to fetch an image or build from source: error building: executor failed running [/bin/sh -c SECRET_KEY_BASE=DUMMY ./bin/rails assets:precompile]: exit code: 1

What the heck?

If this was my first deploy I'd think that something was going on with fly but this had been working perfectly. Then I realized it happened once I added Flowbite / tailwindcss to the mix. There are some workarounds to get Flowbite working with Turbo but that involved mixing importmap and node_modules a bit.

So the fix was to delete my DockerFile, but not the fly.toml and regenerate the DockerFile with fly deploy. The let the fly console appropriately add the node build steps and allowed my deployments to work as intended.