Run Elm and lunarvim in a devcontainer

Let's use docker-compose

As your project grows you'll need eg. sql, nginx etc.
This setup will prepare your project for this.

This dev-environment is using elm-watch.

.devcontainer/d-c-lunarvim.yml

name: d-c-lunarvim-x

services:
  lvim:
    build:
      context: .
      dockerfile: Dockerfile.lunarvim
    networks:
      - internal  # Ensure DevContainer connects to the same network
    volumes:
      - lvim-cs-dependency-cache:/home/lunaruser/.elm
      - ..:/workspace
    command: ["sleep", "infinity"]

volumes:
  lvim-cs-dependency-cache:

networks:
  internal:
    driver: bridge

.devcontainer/devcontainer.json

{
    "name": "lunarvim-devcontainer",
    "service": "lvim",
    "dockerComposeFile": "d-c-lunarvim.yml",
    "mounts": [
        "source=${localEnv:HOME}/.bashrc,target=/home/lunaruser/.bashrc,type=bind",
        "source=lvim-cs-dependency-cache,target=/home/lunaruser/.elm,type=volume"

      ],
    "workspaceFolder": "/workspace",
    // In order to make elm-watch pick up changes
    "containerEnv": {
        "CHOKIDAR_USEPOLLING": "true"
    },
    // Configure tool-specific properties.
    "customizations": {
        // Configure properties specific to VS Code.
        "vscode": {
            // Add the IDs of extensions you want installed when the container is created.
            "extensions": [
                "Elmtooling.elm-ls-vscode",
                "ritwickdey.LiveServer",
                "streetsidesoftware.code-spell-checker",
                "GitHub.copilot-chat",
                "GitHub.copilot",
                "eamodio.gitlens",
                "elmTooling.elm-ls-vscode",
                "kisstkondoros.vscode-gutter-preview",
                "mongodb.mongodb-vscode"
            ]
        }
    }
}

.devcontainer/Dockerfile.lunarvim

# Use a stable version of Alpine as the base image
FROM alpine:3.20.3

# Set up the working directory
WORKDIR /tmp

# Set environment variables
ENV HOME_DIR="/home/lunaruser"
ENV LV_BRANCH="release-1.4/neovim-0.9"
ENV PATH="$PATH:$HOME_DIR/.local/bin"

# Install dependencies
RUN apk update && \
    apk add --no-cache \
        yarn \
        git \
        python3 \
        cargo \
        neovim \
        ripgrep \
        alpine-sdk \
        bash \
        curl \
        nodejs \
        npm \
        sudo \
        libc6-compat  # Install if needed for compatibility with Elm binaries

# Configuring Elm version
ARG ELM_VERSION=latest-0.19.1
ARG ELM_TEST_VERSION=latest-0.19.1
ARG ELM_FORMAT_VERSION=latest-0.19.1

# This Dockerfile adds a non-root user with sudo access.
ARG USERNAME=lunaruser
ARG USER_UID=1000
ARG USER_GID=$USER_UID

# Add a non-root user and group
RUN addgroup -S $USERNAME && \
    adduser -S $USERNAME -G $USERNAME --shell /bin/sh

# Install Elm using the provided method, elm-test and elm-format via npm
RUN export DEBIAN_FRONTEND=noninteractive && \
    # Install Elm binary
    curl -L -o elm.gz https://github.com/elm/compiler/releases/download/0.19.1/binary-for-linux-64-bit.gz && \
    gunzip elm.gz && \
    chmod +x elm && \
    mv elm /usr/local/bin/elm && \
    # Install elm-test and elm-format via npm
    npm install --global \
        elm-test@${ELM_TEST_VERSION} \
        elm-format@${ELM_FORMAT_VERSION} \
        elm-watch@beta && \
    # [Optional] Update UID/GID if needed
    if [ "$USER_GID" != "1000" ] || [ "$USER_UID" != "1000" ]; then \
        groupmod --gid $USER_GID $USERNAME && \
        usermod --uid $USER_UID --gid $USER_GID $USERNAME && \
        chown -R $USER_UID:$USER_GID /home/$USERNAME; \
    fi && \
    # Create the elm cache directory where we can mount a volume
    mkdir /home/$USERNAME/.elm && \
    chown $USERNAME:$USERNAME /home/$USERNAME/.elm

# Switch to the non-root user
USER $USERNAME

# Run LunarVim installation as the non-root user
RUN curl -s https://raw.githubusercontent.com/lunarvim/lunarvim/$LV_BRANCH/utils/installer/install.sh | \
    bash -s -- --no-install-dependencies

# Define the volume for the .bashrc file
VOLUME /home/lunaruser/

# Set default command to open LunarVim - when running directly in a docker container
# CMD ["/home/lunaruser/.local/bin/lvim"]

Personal preferences:
.vscode/settings.json

{
    "liveServer.settings.root": "/wwwroot",
    "editor.formatOnSave": true,
    "files.autoSave": "onFocusChange",
    "editor.defaultFormatter": "elmTooling.elm-ls-vscode"
}

Run elm-format on save

Open the config.

~/.config/lvim/config.lua

lvim.format_on_save.enabled = true
lvim.format_on_save.allow_filetypes = { "elm" }

local formatters = require ("lvim.lsp.null-ls.formatters")
formatters.setup({
    {
        exe = "elm-format",
        filetypes = { "elm" },
    }
})

I'm stil to find out how to load your own personal configurations (*.lua files)

Comments

[Theodor Heiselberg]

Hi great question ☺️
The answer is tooling. Every project I work on also involves databases and various other services. Using vs code and devcontainers with all the necessary extensions ties my entire dev environment together with my ide of choice. One ide to rule the entire project 👍
(Hence the usage of docker compose)
Personally I’m not that mush a cli expert to be using the cli exclusively.
What’s your opinion?

[Daniel Hamngren]

Intesting post! But I don’t really understand how you use your devcontainer. Are you using both lunarvim and vs code in your devcontainer? How do you interact with lunarvim when you have your devcontainer running on e.g. codespaces?

What do you see is the best thing with the setup in your post?

[Theodor Heiselberg]

question ☺️
The answer is tooling. Every project I work on also involves databases and various other services. Using vs code and devcontainers with all the necessary extensions ties my entire dev environment together with my ide of choice. One ide to rule the entire project 👍
(Hence the usage of docker compose)
Personally I’m not that mush a cli expert to be using the cli exclusively.
What’s your opinion?