How to fix "<stdin>: hGetLine: end of file" when running stack build --file-watch in a docker-compose command

Question

I try to have an auto rebuild & rexecute setup for my haskell RPC server code within a docker-compose service. The command is a bash script with stack build --file-watch (and another command to start the binary when it changes but this works). The problem is that, no matter what I try, the stack build --file-watch command fails with a cryptic error <stdin>: hGetLine: end of file.

I do not understand why I get this error, especially because if I run the same command using docker-compose run bd-service bash -l -c "./bd-service/compile_hs_and_run.sh", it works as expected. I believe it's a problem of how bash is handled when docker-compose up is executed rather than a problem of stack itself, but I'll admit I'm clueless.

Also note that:

• removing the --file-watch option makes the script working
• replacing the --file-watch with --file-watch-poll does not change anything

This is the service definition:

  # this is my service definition in docker-compose.yml
  bd-service:
    build:
      context: '.'
      dockerfile: 'dockerfiles/bd_heroku_service.Dockerfile'
      args:
        UID: "$UID"
    command:  bash -l -c "./bd-service/compile_hs_and_run.sh"
    user: "$UID"
    volumes:
      - .:/app/user

This is the relevant dockerfile:

# Inherit from bd_heroku_node image
FROM bd_heroku_node

ENV LANG en_US.UTF-8
# Stack stores binaries in /root/.local/bin
ENV PATH /root/.local/bin:$PATH

# Heroku assumes we'll put everything in /app/user
RUN mkdir -p /app/user/bd-service
WORKDIR /app/user

USER root

ARG STACK_VERSION=2.1.3
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/local/bin '*/stack'
USER appuser
# . here means the entire bd-bootstrap repo, context should be set accordingly (to bd-bootstrap)
RUN stack setup --resolver lts-14.10;

USER appuser
RUN mkdir -p /app/user/bd-common
RUN mkdir -p /app/user/bd-service

COPY bd-common/*.yaml /app/user/bd-common/

RUN cd /app/user/bd-common; stack build --only-dependencies;

RUN stack install fswatcher;

And then my bash file compile_hs_and_run:

#! /bin/bash
DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"

cd $DIR
echo "We are at "
pwd
echo "start";

stack build --verbose --file-watch

# The next command is commented because it works :
# /app/.local/bin/fswatcher --path /app/user/bd-service/.stack-work/install stack run bd-service-exe &


echo "it's over"

When starting with docker-compose up bd-service it fails with these logs:

bd-service_1       | We are at 
bd-service_1       | /app/user/bd-service
bd-service_1       | start
bd-service_1       | Version 2.1.3, Git revision 0fa51b9925decd937e4a993ad90cb686f88fa282 (7739 commits) x86_64 hpack-0.31.2
bd-service_1       | 2019-10-21 07:23:02.631167: [debug] Checking for project config at: /app/user/bd-service/stack.yaml
bd-service_1       | 2019-10-21 07:23:02.634794: [debug] Loading project config file stack.yaml
bd-service_1       | 2019-10-21 07:23:02.641395: [error] <stdin>: hGetLine: end of file
bd-service_1       | it's over

Answer 1

A simple workaround for my issue is to pipe cat to the stack build --file-watch. I got inspired by this thread on stack exchange: https://unix.stackexchange.com/a/103893.

Thus replacing stack build --verbose --file-watch by cat | stack build --verbose --file-watchworks like a charm. I do feel like this is not "normal" to some extent but whatever...

The thing that made it work is actually the stdin_open: true option in the docker-compose.yml, piping the cat command didn't do anything...