Improve Dockerfile

Dockerfile

-FROM ubuntu:18.04
+# should match the GHC version of the stack.yaml resolver
+FROM haskell:8.10.4 AS ihaskell_base
 
-ARG STACK_VERSION=2.7.3
-ARG RESOLVER=lts-17.4
+# Install Ubuntu packages needed for IHaskell runtime
+RUN apt-get update && \
+    apt-get install -y \
+            libblas3 \
+            libcairo2 \
+            liblapack3 \
+            libmagic1 \
+            libpango-1.0-0 \
+            libzmq5 \
+        && \
+    rm -rf /var/lib/apt/lists/*
+
+FROM ihaskell_base AS builder
 
-# Install all necessary Ubuntu packages
-RUN apt-get update && apt-get install -y python3-pip libgmp-dev libmagic-dev libtinfo-dev libzmq3-dev libcairo2-dev libpango1.0-dev libblas-dev liblapack-dev gcc g++ wget && \
+# Install Ubuntu packages needed for IHaskell build
+RUN apt-get update && \
+    apt-get install -y \
+            libblas-dev \
+            libcairo2-dev \
+            liblapack-dev \
+            libmagic-dev \
+            libpango1.0-dev \
+            libzmq3-dev \
+        && \
     rm -rf /var/lib/apt/lists/*
 
+WORKDIR /build
+
+# Build snapshot
+COPY stack.yaml stack.yaml
+COPY ihaskell.cabal ihaskell.cabal
+COPY ipython-kernel ipython-kernel
+COPY ghc-parser ghc-parser
+COPY ihaskell-display ihaskell-display
+RUN stack setup
+RUN stack build --only-snapshot
+
+# Build IHaskell itself.
+# Don't just `COPY .` so that changes in e.g. README.md don't trigger rebuild.
+COPY src src
+COPY html html
+COPY main main
+COPY LICENSE LICENSE
+RUN stack install --local-bin-path ./bin/
+
+# Save resolver used to build IHaskell
+RUN sed -n 's/resolver: \(.*\)/\1/p' stack.yaml | tee resolver.txt
+
+# Save third-party data files
+RUN mkdir /data && \
+    snapshot_install_root=$(stack path --snapshot-install-root) && \
+    cp $(find ${snapshot_install_root} -name hlint.yaml) /data
+
+FROM ihaskell_base AS ihaskell
+
 # Install Jupyter notebook
+RUN apt-get update && \
+    apt-get install -y python3-pip && \
+    rm -rf /var/lib/apt/lists/*
 RUN pip3 install -U jupyter
 
-ENV LANG C.UTF-8
-ENV LC_ALL C.UTF-8
+# Create runtime user
 ENV NB_USER jovyan
 ENV NB_UID 1000
-ENV HOME /home/${NB_USER}
-
 RUN adduser --disabled-password \
     --gecos "Default user" \
     --uid ${NB_UID} \
     ${NB_USER}
 
-RUN wget -qO- https://github.com/commercialhaskell/stack/releases/download/v$STACK_VERSION/stack-$STACK_VERSION-linux-x86_64.tar.gz | tar xz --wildcards --strip-components=1 -C /usr/bin '*/stack'
+# Create directory for storing ihaskell files
+ENV IHASKELL_DATA_DIR /usr/local/lib/ihaskell
+RUN mkdir -p ${IHASKELL_DATA_DIR} && chown ${NB_UID} ${IHASKELL_DATA_DIR}
 
-# Set up a working directory for IHaskell
-RUN install -d -o ${NB_UID} -g ${NB_UID} ${HOME} ${HOME}/ihaskell
-WORKDIR ${HOME}/ihaskell
+# Set up + set hlint data directory
+ENV HLINT_DATA_DIR /usr/local/lib/hlint
+COPY --from=builder --chown=${NB_UID} /data/hlint.yaml ${HLINT_DATA_DIR}/
+ENV hlint_datadir ${HLINT_DATA_DIR}
 
+# Set current user + directory
 USER ${NB_UID}
+ENV HOME /home/${NB_USER}
+WORKDIR ${HOME}
 
-# Install dependencies for IHaskell
-COPY --chown=${NB_UID}:${NB_UID} stack.yaml stack.yaml
-COPY --chown=${NB_UID}:${NB_UID} ihaskell.cabal ihaskell.cabal
-COPY --chown=${NB_UID}:${NB_UID} ipython-kernel ipython-kernel
-COPY --chown=${NB_UID}:${NB_UID} ghc-parser ghc-parser
-COPY --chown=${NB_UID}:${NB_UID} ihaskell-display ihaskell-display
-
-RUN stack setup
-RUN stack build --only-snapshot
-
-# Install IHaskell itself. Don't just COPY . so that
-# changes in e.g. README.md don't trigger rebuild.
-COPY --chown=${NB_UID}:${NB_UID} src ${HOME}/ihaskell/src
-COPY --chown=${NB_UID}:${NB_UID} html ${HOME}/ihaskell/html
-COPY --chown=${NB_UID}:${NB_UID} main ${HOME}/ihaskell/main
-COPY --chown=${NB_UID}:${NB_UID} LICENSE ${HOME}/ihaskell/LICENSE
-
-RUN stack build && stack install
-RUN mkdir -p ${HOME}/.stack/global-project && \
-    echo "packages: []\nresolver: ${RESOLVER}\n" > ${HOME}/.stack/global-project/stack.yaml
+# Set up global project
+COPY --from=builder --chown=${NB_UID} /build/resolver.txt /tmp/
+RUN stack setup --resolver=$(cat /tmp/resolver.txt) --system-ghc
 
-# Run the notebook
-ENV PATH $(stack path --local-install-root)/bin:$(stack path --snapshot-install-root)/bin:$(stack path --compiler-bin):/home/${NB_USER}/.local/bin:${PATH}
-RUN ihaskell install --stack
-WORKDIR ${HOME}
+# Install + setup IHaskell
+COPY --from=builder --chown=${NB_UID} /build/bin/ihaskell /usr/local/bin/
+COPY --from=builder --chown=${NB_UID} /build/html ${IHASKELL_DATA_DIR}/html
+RUN export ihaskell_datadir=${IHASKELL_DATA_DIR} && \
+    ihaskell install --stack
 RUN jupyter notebook --generate-config
+
 CMD ["jupyter", "notebook", "--ip", "0.0.0.0"]

stack.yaml

+# the GHC version of this resolver needs to match the GHC version in Dockerfile
 resolver: lts-18.5
 allow-newer: true