In the default Dockerfile, mix assets.deploy downloads tailwind & esbuild every time assets change

[jyc]

Thanks for making Phoenix! I noticed that in the default Dockerfile mix assets.deploy downloads tailwind & esbuild every time assets change:

phoenix/priv/templates/phx.gen.release/Dockerfile.eex

Lines 46 to 55 in 69685f7

	RUN mix deps.compile
	COPY priv priv
	COPY lib lib
	<%= if assets_dir_exists? do %>
	COPY assets assets
	# compile assets
	RUN mix assets.deploy

Do you think the default could be changed to run

mix tailwind.install
mix esbuild.install

... after mix deps.compile and before mix assets.deploy? This should make most Docker image builds faster because they won't have to download tailwind/esbuild every time anything in priv, lib, or assets changes.

I'd be happy to open a small PR to do this if it's alright with you!

The only challenge is that it'd have to handle --no-tailwind and --no-esbuild. Happy to take a stab at handling that too with some pointers; a cursory search for no-tailwind didn't turn up anything: https://github.com/search?q=repo%3Aphoenixframework%2Fphoenix+no-tailwind&type=code

[SteffenDE]

@jyc I think it should be possible to add mix assets.setup instead of adding the tailwind and esbuild installs separately. We'd only need to check if the assets.setup task is actually available when generating the Dockerfile:

RUN mix deps.compile
<%= if @assets_setup_available? do %>mix assets.setup<% end %>

and adding the binding here:

phoenix/lib/mix/tasks/phx.gen.release.ex

Lines 246 to 250 in c848a84

	Keyword.merge(binding,
	debian: @debian,
	debian_vsn: debian_vsn,
	elixir_vsn: elixir_vsn,
	otp_vsn: otp_vsn

            elixir_vsn: elixir_vsn,
+           otp_vsn: otp_vsn,
+           assets_setup_available?: Keyword.has_key?(Mix.Project.config()[:aliases], :"assets.setup")

If you want to give it a go and send a PR, I'll be happy to review it.

[rhcarvalho]

I do an explicit mix assets.setup after mix deps.compile in a Dockerfile, can confirm it leads to better caching.