stack --nix image container does not generate an image

[vandenoever]

General summary/comments (optional)

stack --nix image container --image docker.img

does not generate a file docker.img.

Steps to reproduce

1. Create a stack project with a file stack.yaml
2. Run command stack --nix -v image container --image docker.img.
3. Observe that the program runs and exits with status 0 and no error message.
4. Observe that there is no file docker.img.

Include any .yaml configuration if relevant.

stack.yaml does not contain a image: section.

Expected

A docker image named docker.img.

Actual

No docker image.

Stack version

$ stack --version
Version 1.4.0 x86_64

Method of installation

• NixOS

[vandenoever]

On Ubuntu 16.04 with stack 1.4.0, also no Docker image is generated after running

stack new test simple
cd test
stack --nix -v image container --image docker.img

The executable test is built, but no docker image is produced.

[mgsloan]

Not sure what the semantics or purpose of nix + docker would be. Perhaps just use docker?