Question about the dockerfile in installation docs

[oskolist]

the docs contains this section to show proper usage of templ generate in Dockerfiles but i don't understand it, fetch-stage stage was never used. so what was the point? (i don't think doing go mod download in a complete isolated build stage will take any effect on the caching behaviour either, because it will not cached). is this even correct or it's just something that AI generate and pushed to docs without checking?

# Fetch
FROM golang:latest AS fetch-stage
COPY go.mod go.sum /app
WORKDIR /app
RUN go mod download

# Generate
FROM ghcr.io/a-h/templ:latest AS generate-stage
COPY --chown=65532:65532 . /app
WORKDIR /app
RUN ["templ", "generate"]

# Build
FROM golang:latest AS build-stage
COPY --from=generate-stage /app /app
WORKDIR /app
RUN CGO_ENABLED=0 GOOS=linux go build -o /app/app

# Test
FROM build-stage AS test-stage
RUN go test -v ./...

# Deploy
FROM gcr.io/distroless/base-debian12 AS deploy-stage
WORKDIR /
COPY --from=build-stage /app/app /app
EXPOSE 8080
USER nonroot:nonroot
ENTRYPOINT ["/app"]

[a-h]

It's a modified version of https://docs.docker.com/guides/golang/build-images/#multi-stage-builds

Looking at it with fresh eyes, looks like the fetch-stage doesn't have any effect.

Feel free to create a PR if you have a better way. Personally, I commit _templ.go files and build Docker containers using Nix tooling.

[oskolist]

@a-h thanks for quick anwser and +1 for using Nix
I will create a PR and modify it to use cached layer once I get some free time.

[oskolist]

@a-h a quick question, does templ will care about the templ version in go.mod other than showing a warning about it?
i'm asking this because i want to know should i change the templ version in go.mod to same as docker image version before doing templ generate(using it's docker image)? does not doing that it any downside other than just a warning(which can be disabled easily)?

[a-h]

It's just a warning because a mismatch between what the generator generates and the version of the runtime that's installed in the project could cause issues:

• The newly generated code may rely on features not in the templ module in the go.mod, so you'd get a compilation error and wonder why.
• The old code might have a bug in the templ module in the go.mod, so it might be worth updating, since if the CLI is newer, the go.mod version can definitely be updated.

I think it's best to make sure that the templ versions match by bumping up the go.mod.