extends not supported in version 3 schema

[chaosk]

I'm running Docker 1.13.0-rc4 and current master (545153f) of Compose.

I tried to deploy a stack using following docker-compose.yml file:

version: "3"
services:
  base:
    image: hello-world
  extending:
    extends: base
    labels:
      - "label=test"

Got following in response:

$ docker stack deploy --compose-file ./docker-compose.yml test
Compose file contains unsupported options:

extends: Support for `extends` is not implemented yet. Use `docker-compose config` to generate a configuration with all `extends` options resolved, and deploy from that.

I found an issue about it in Docker's repo (moby/moby#29304) and attempted to run the command given by the error message, which resulted in:

$ docker-compose config
ERROR: The Compose file './docker-compose.yml' is invalid because:
Unsupported config option for services.extending: 'extends'

[shin-]

cc @dnephin

[chaosk]

I've been wondering, wouldn't adding compose/config/config_schema_v2.1.json#L124-L140 to config_schema_v3.0.json work? I tried doing that locally and it generated output correctly, but I guess it could be breaking other uses.

[mhyz]

Note for others struggeling with this issue:

Regarding to the docs:
"extend" is NOT yet supported with a version 3 compose file.

https://docs.docker.com/compose/compose-file/#extends

This option is not yet supported when deploying a stack in swarm mode with a (version 3) Compose file. Use docker-compose config to generate a configuration with all extends options resolved, and deploy from that.

[viztastic]

Do we know which version of docker 'extends' will be supported in compose v3? Even if just Indicative?

[byrnedo]

I've tried the docker-compose config command and it says the same error.
Resorted to perl: https://gist.github.com/byrnedo/7ac5e461ba0866299fdd94899bebdbd9

[nicodmf]

+1 for supporting extend in v3

[martsa1]

Would it be a lot of effort to support the use of extends when using docker-compose not in swarm mode?

I use extends to manage production, development and test setups and would like to continue doing so outside of swarm mode, but eventually use docker stack deploy with the production variant. I can probably use @byrnedo's script above to achieve the latter, but I'm blocked running docker-compose up on a v3 file containing extends... :/

[nicodmf]

This is the same for me, extends is a really usefull option, which for know cause a hole in hour workflow deployment

[willseward]

The docs seem a bit misleading ATM:

Note: This option is not yet supported when deploying a stack in swarm mode with a (version 3) Compose file. Use docker-compose config to generate a configuration with all extends options resolved, and deploy from that.

It reads like docker-compose config can be used to generate a v3 docker stack deploy-compatible docker-compose.yml file, but that is obviously not the case.

[artheus]

@willseward I strongly agree with you on this. docker-compose config should obviously be able to use the extends configuration keyword even when using version 3, according to the documentation.

It's a very ugly hacky solution to do what I'm forced to do right now:

$ docker-compose config | sed "s#version: '2\.1'#version: '3'#g"

EDIT: This is especially ugly since docker-compose will treat it as 2.1 version syntax, so it will certainly force developers into hacky solutions which will probably also be limited on certain version 3 features.
Maybe some people will create their own tools to, for the time being, replace docker-compose. I sure am tempted to do that.