Precompile fails after adding tailwindcss-rails + npm modules

[sdhull]

Background: while my project is still young, I decided to switch from the "old & busted" bootstrap to "new hotness" Tailwind. Decided to use Flowbite so I don't have to build everything from scratch.

Anyway I added the tailwindcss-rails gem and decided to use Node 18 + Yarn 3 (with node_modules/). So I did yarn add flowbite and yarn add flowbite-typography. Everything works great locally, even the precompile task runs fine.

I regenerated my Dockerfile with rails g dockerfile. The first problem I ran into was installing yarn. Apparently you can't npm install -g [email protected], so I had to customize it in order to install Yarn 3

RUN curl -sL https://github.com/nodenv/node-build/archive/master.tar.gz | tar xz -C /tmp/ && \
    /tmp/node-build-master/bin/node-build "${NODE_VERSION}" /usr/local/node && \
    corepack enable && \
    corepack prepare yarn@$YARN_VERSION --activate && \
    rm -rf /tmp/node-build-master

So that got me past that part. But now precompile is failing with:

 => ERROR [build 10/10] RUN SECRET_KEY_BASE=DUMMY ./bin/rails assets:precompile                                                                                              2.7s
------
 > [build 10/10] RUN SECRET_KEY_BASE=DUMMY ./bin/rails assets:precompile:
2.595
2.597 Rebuilding...
2.648 Error: Cannot find module 'flowbite/plugin'
2.648 Require stack:
2.648 - /rails/config/tailwind.config.js
2.648     at Function.Module._resolveFilename (node:internal/modules/cjs/loader:933:15)
2.648     at Function._resolveFilename (pkg/prelude/bootstrap.js:1955:46)
2.648     at Function.resolve (node:internal/modules/cjs/helpers:108:19)
2.648     at _resolve (/snapshot/tailwindcss/node_modules/jiti/dist/jiti.js:1:241025)
2.648     at jiti (/snapshot/tailwindcss/node_modules/jiti/dist/jiti.js:1:243309)
2.648     at /rails/config/tailwind.config.js:34:5
2.648     at jiti (/snapshot/tailwindcss/node_modules/jiti/dist/jiti.js:1:245784)
2.648     at /snapshot/tailwindcss/lib/lib/load-config.js:37:30
2.648     at loadConfig (/snapshot/tailwindcss/lib/lib/load-config.js:39:6)
2.648     at Object.loadConfig (/snapshot/tailwindcss/lib/cli/build/plugin.js:135:49) {
2.648   code: 'MODULE_NOT_FOUND',
2.648   requireStack: [ '/rails/config/tailwind.config.js' ]
2.648 }

I have zero idea how to debug this. I'd love to just be able to inspect the filesystem at this point. Why hasn't docker introduced a debugger line so I can inspect failing builds?? 😭

[sdhull]

OK update: I forgot I also added the --cache option because I wanted to speed up my builds. Also I copied the Dockerfile into a Dockerfile.partial and deleted the failing command and everything that came after so I could run the resulting image and poke around. I realized immediately that there was no node_modules directory.

I think the issue boils down to this:

# Install node modules
COPY --link package.json yarn.lock ./
RUN --mount=type=cache,id=bld-yarn-cache,target=/root/.yarn \
    YARN_CACHE_FOLDER=/root/.yarn yarn install --frozen-lockfile

# ... omitted other stuff

# Precompiling assets for production without requiring secret RAILS_MASTER_KEY
RUN SECRET_KEY_BASE=DUMMY ./bin/rails assets:precompile

At first I was thinking the cache mount was to blame, but after some experimentation, I realized that's not it. The issue is (apparently?) that node_modules gets clobbered by COPY --link . .

Re-ordering these so that COPY comes before yarn install seems to help but I'm a bit worried this is gonna invalidate all layers that come afterward on every deploy. Nonetheless, progress.

[sdhull]

I guess these lines are right next to each other, so it's just the yarn install that will have to happen on every deploy. But at least there's a persistent yarn cache 😎

[rubys]

The following code in the template should have installed yarn with corelib:

https://github.com/fly-apps/dockerfile-rails/blob/main/lib/generators/templates/_install_node.erb#L19-L30

If node_modules in your .dockerignore file? Either way, I can't explain why it is empty after the COPY statement.

[sdhull]

Yes, it is... I didn't add it though, it was generated when I was getting fly.io deployment working 🤔
And to be fair, at that point I didn't have a package.json file or anything in node_modules/ yet

[sdhull]

Should I remove it from .dockerignore?

[rubys]

If you used fly launch and didn't yet have a package.json file, then you weren't using dockerfile-rails. That could explain the yarn install issues.

Yes, you want node_modules in your .dockerignore.

I'll try to reproduce the caching problem tomorrow.