Compose: Compose file invalid because [...]. volumes contain an invalid type, it should be a string

[chiffa]

Description of the issue

Upon conversion from the short syntax of volume mounting to the long syntax, paths including environment variables in the source definition of the volume directory are no more properly parsed.

Here is the sample of volume mounting instruction with long syntax:

    volumes:
      - type: bind
        source: $HOME/app/docker-app/db-data
        target: /data/db
        bind:
          propagate: rshared

The resulting error is:

ERROR: The Compose file './docker-compose.yml' is invalid because:
services.app.volumes contains an invalid type, it should be a string

Here is the prior short syntax that did not raise any errors:

    volumes:
          - $HOME/app/docker-app/db-data:/data/db

Both of the instructions are issued for version: "2" of docker-compose, but the issue remains in version: "3".

Context information (for bug reports)

Output of docker-compose version

docker-compose version 1.18.0, build 8dd22a9
docker-py version: 2.6.1
CPython version: 2.7.13
OpenSSL version: OpenSSL 1.0.1t  3 May 2016

Output of docker version

Client:
 Version:      17.03.0-ce
 API version:  1.26
 Go version:   go1.7.5
 Git commit:   3a232c8
 Built:        Tue Feb 28 07:57:58 2017
 OS/Arch:      linux/amd64

Server:
 Version:      17.03.0-ce
 API version:  1.26 (minimum version 1.12)
 Go version:   go1.7.5
 Git commit:   3a232c8
 Built:        Tue Feb 28 07:57:58 2017
 OS/Arch:      linux/amd64
 Experimental: false

Output of docker-compose config
(Make sure to add the relevant -f and other flags)

ERROR: The Compose file './docker-compose.yml' is invalid because:
services.app.volumes contains an invalid type, it should be a string

Steps to reproduce the issue

1. define a docler-compose file containing the following instruction:

    volumes:
      - type: bind
        source: $HOME/app/docker-app/db-data
        target: /data/db
        bind:
          propagate: rshared

1. Issuue a docker-compose build

Observed result

ERROR: The Compose file './docker-compose.yml' is invalid because:
services.app.volumes contains an invalid type, it should be a string

Expected result

Proper volume mapping, consistent with short syntax

Stacktrace / full error message

ERROR: The Compose file './docker-compose.yml' is invalid because:
services.app.volumes contains an invalid type, it should be a string

Additional information

Ubuntu 14.04 LTS 64 Bit, docker-compose installed and updated with apt-get

[chiffa]

Closed: issue was due to the wrong version of docker-compose declared at the beginning of the docker-compose.yml

[krinsman]

In case this helps anyone else, an example of a correct version to use would be "3.7", see e.g. here: https://docs.docker.com/compose/compose-file/#long-syntax-3

"3" is insufficient.