[Haskell-cafe] developing using .devcontainer in vscode

[Han Joosten]

Hi Cafe,

I am trying to set up a useful development container for an open source
project I am working on. I have created an image on top of the official
Haskell image, expecting a proper installation of ghcup, cabal, stack and
hls. The Dockerfile looks like this:

FROM haskell:8.10

ARG USERNAME=vscode


ENV USERNAME=${USERNAME} \
    USER_UID=1000 \
    USER_GID=1000 \
    DEBIAN_FRONTEND=noninteractive \
    LANG=C.UTF8 \
    WDIR=/home/${USERNAME}

RUN apt-get update && \
    apt-get upgrade -y && \
    apt-get install -y git

RUN groupadd --gid $USER_GID $USERNAME && \
    useradd -ms /bin/bash -K MAIL_DIR=/dev/null --uid $USER_UID --gid
$USER_GID -m $USERNAME && \
    mkdir -p /etc/sudoers.d && \
    echo $USERNAME ALL=\(root\) NOPASSWD:ALL > /etc/sudoers.d/$USERNAME && \
    chmod 0440 /etc/sudoers.d/$USERNAME

USER ${USER_UID}:${USER_GID}

WORKDIR ${WDIR}

RUN stack update

# Add just the .cabal file to capture dependencies
COPY ./package.yaml ${WDIR}/package.yaml
COPY ./stack.yaml ${WDIR}/stack.yaml

# Docker will cache this command as a layer, freeing us up to
# modify source code without re-installing dependencies
# (unless one of the copied files changes!)
RUN stack build --only-dependencies -j4

COPY . ${WDIR}

ENV DEBIAN_FRONTEND=dialog

ENTRYPOINT ["/bin/bash"]


The above image is built and pushed to dockerhub. Then, in the vscode
project, I have a .devcontainer directory with the following Dockerfile:

FROM ampersandtarski/ampersand-devcontainer:latest

ENV DEBIAN_FRONTEND=dialog

ENTRYPOINT ["/bin/bash"]

The idea is that all the building of the dependencies is already done in
the first image. That takes a lot of time, so this is supposed to be a
great timesaver (though the image itself is huge).
However, when I open the project inside the container, I get the following
error:
[image: image.png]

If I reload the window, I get the following errors:
[image: image.png]

Long story short, I am not sure how to use the official Haskell image for
development in my project. I must be missing something. I have been trying
lots of things, but without succes. I hope it is possible to have an image
built on top of the official Haskell file that contains all prebuilt
dependencies of my project. Are my expectations realistic? If so, what am I
missing?
Any help is much appreciated.
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