Build context is wrong when COMPOSE_FILE is being used

[achekulaev]

When COMPOSE_FILE directive is being used, docker-compose uses wrong relative path/build context for build instructions.

Demonstration.
Directory /Users/alexei.chekulaev/tmp/bug_demo

Structure:

bug_demo/
  conf/
    docker-compose.yml
  build/
    Dockerfile

docker-compose.yml contents:

version: "2.1"

services:
  test:
    build: build

Actual result when building in /Users/alexei.chekulaev/tmp/bug_demo:

$ pwd
/Users/alexei.chekulaev/tmp/bug_demo

$ COMPOSE_FILE="conf/docker-compose.yml" docker-compose config
ERROR: build path /Users/alexei.chekulaev/tmp/bug_demo/conf/build either does not exist, is not accessible, or is not a valid URL.

So docker-compose was looking for build dir in /Users/alexei.chekulaev/tmp/bug_demo/conf which is wrong.

Expected result: docker-compose should use CWD as current path, not the path where first config file was found.

[achekulaev]

Relates to: #4857

[shin-]

This works as documented: https://docs.docker.com/compose/compose-file/#context

When the value supplied is a relative path, it is interpreted as relative to the location of the Compose file.

[achekulaev]

@shin- thanks for a quick reply. Is there a way to set context to current working dir without providing the full path?

I also have a couple of side notes:

1. Documentation says when the value is provided. I did not provide value, but docker-compose assumes . that translates into the path of the first yml provided. That is not documented and not obvious.

2. "The" Compose file does not make full sense since COMPOSE_FILE is multivalue, that in my real case contains 4 files. In this case "the file" is actually the first one. Which is again not obvious and not documented.

[shin-]

In your case, I believe simply changing build to ../build will do the trick.

[achekulaev]

The case in the ticket is just an artificial example. The real case is much more complex. I have central yml files. And I have per-project yml files that override some values of those central yml files, and also per-project Dockerfile.

/base.yml
/volumes.yml

/arbitrary/path/projectA/project.overrides.yml
/arbitrary/path/projectA/Dockerfile

/other/arbitrary/path/projectB/project.overrides.yml
/other/arbitrary/path/projectB/Dockerfile

My COMPOSE_FILE has all of them:

COMPOSE_FILE="/base.yml;/volumes.yml;/arbitrary/path/projectA/project.overrides.yml"

And what I actually need is to build images in the context of a project, not in the context of the base.yml.

To do that right now, in project.yml my developers have to write exact project path:

...
  build: /other/arbitrary/path/projectB

Base files won't move, but projects can. When project files move (or when used on other OS), exact path will stop working.
Would be great to be able to write something pointing to the current working directory instead.

...
  # this is current working directory, not the path of the central.base.yml
  build: ./

[shin-]

You can do

  build: $PWD/projectB

[achekulaev]

@shin- got it, thank you.