dockerfile and compose for local dev with elixir:alpine

docker-compose.yml

version: '3.9'

services:
  app:
    build:
      args:
        UID: ${UID}
        USER: ${USER}
    command: elixir -S mix phx.server
    ports:
      - 4000:4000
    volumes:
      - .:/app:cached
      - build:/app/_build
      - deps:/app/deps
      - node_modules:/app/assets/node_modules
      
volumes:
  build:
  deps:
  node_modules:

Dockerfile

FROM elixir:1.13-alpine AS base

RUN apk add --no-cache \
    bash \
    inotify-tools \
    nodejs npm \
    openssl

WORKDIR /app
CMD ["mix", "phx.server"]

FROM base AS local

ARG UID
ARG USER
RUN adduser -u $UID -D -h /home/$USER -s /bin/bash $USER

RUN mkdir -p /app/_build && \
    mkdir -p /app/deps && \
    mkdir -p /app/assets/node_modules && \
    chown -R $USER /app

USER $USER

# these install to user home dirs
RUN mix local.hex --force && \
    mix local.rebar --force