Choose a name for depending on another compose file

[ndeloof]

See #318

[thaJeztah]

Given that "extends" already supports files (#318 (comment)), wouldn't it make sense to extend that to allow the file to have an optional scheme (file://, https://) ?

[thaJeztah]

(also curious about recursion; if the linked file also contains external links)

[ndeloof]

@thaJeztah this has been suggested already, I'd prefer we consider support for "other than file" reference to be addressed at once, so that this can be used for --file, extends and this new feature at once.

[ndeloof]

The main reason I would prefer import is that Compose.yaml syntax reflect it's original implementation in python, by adopting the snake_case syntax for attribute, so we could follow this with the python import keyword here.

[chrisbecke]

import and include have different implications. include implies you can think of the result as a single large document with the included documents pasted in verbatim at the point of the include directive.
import implies that the target document is imported as a module and there is some degree of namespacing to protect imported things from overlapping.
I think include is closer to the truth of what is happening here.

[ndeloof]

things are not written in stone. We could later have options to only impo-clude a subset of a compose file by includes/excludes rules, rename resources in case of conflicts, or define a namespace/prefix to be added to those... future will tel depending on real world usage of this. I don't think the keyword being used, which you might give some specific meaning based on your own favorite coding language, has any major impact here

[thaJeztah]

The alternative could be to allow extends at levels higher up;

services:
  extends:
      file: frontend/docker-compose.yaml

services:
  extends:
      file: http://localhost:8080/projects/servicea/fig.yml

volumes:
  extends:
      file: http://localhost:8080/projects/servicea/fig.yml

extends:
    file: http://localhost:8080/projects/servicea/fig.yml
services:
  web:
    # ...

One possible requirement for that would be to remove the requirement for services: to be present; users may want to define "partial" compose files (e.g. only containing volumes, or only containing networks).

[thaJeztah]

• I guess Proposal: provide (pre-defined) variables compose-spec/compose-spec#248 also becomes more relevant if multiple files are to be merged (and becoming more common)

[jmaitrehenry]

If the external file is use as a base and the current file will extend it by adding some key/value to the yaml or by overriding some value, extends is a better fit because it include the intention.

With just import/require/include it's harder to find which one have a precedence over the other one.

Exemple:

# compose.yaml
services:
  db:
    image: mysql:8.1
    import: mysql.yaml
   environment:
     MYSQL_DATABASE: 'my_app_db'
    
# mysql.yaml
image: mysql:8.0
  environment:
    MYSQL_DATABASE: 'my_db'
    MYSQL_USER: 'my_user'
    MYSQL_PASSWORD: 'MyUsErPasSwOrD'
    MYSQL_ROOT_PASSWORD: 'AdMiNPaSsWoRd'
  ports:
    - '3306:3306'

What is the expected result?

I think, with include, we may think that key before the import may be overwritten by the key inside the import, but with extends, it should not be overwritten as the imported file will be use as a base or default and the current file will extend it.

[ndeloof]

the external file will be parsed and imported but no override is supported, this is about depending on resources managed by another team within their own compose file.

[jigso]

There is a documentation about an include command in compose files : https://docs.docker.com/compose/compose-file/14-include/
I don't understand if it is something planned or something deprecated. The include keyword is not accepted of course in current docker-compose, and not mentionned in the documentation of v2 and v3 (https://docs.docker.com/compose/compose-file/compose-file-v3/)
As far as I understand the documentation about include, it should act similarly as many "-f" on the command line.