fix: handle more complex fields during merge

[glours]

Improve the overall merge process for specific attribute format and uniqueness for lists and sequences

closes docker/compose#11417

[milas]

LGTM but note that we need the same for services.*.annotations, services.*.extra_hosts, and services.*.sysctls as well 😬

There might be others, but those are all k-v list or maps, so were easy to identify.

[logopk]

I have noticed problems with duplicate IP subnets. docker-compose version 2.24.2 and 2.24.3

  default:
    driver: bridge
    ipam:
     config:
       - subnet: 172.18.0.0/29  

override:

  default:
    driver: bridge
    ipam:
     config:
       - subnet: 172.23.0.0/29

docker-compose config shows

  default:
    name: apache_default
    driver: bridge
    ipam:
      config:
        - subnet: 172.18.0.0/29
        - subnet: 172.23.0.0/29

Error message on up is:

 ✘ Network apache_default  Error                                                                                                                                  0.0s 
failed to create network apache_default: Error response from daemon: bridge driver doesn't support multiple subnets

This was not a problem so far. config shows the overridden subnet and up starts the container in this subnet

  default:
    name: apache_default
    driver: bridge
    ipam:
      config:
      - subnet: 172.23.0.0/29

if it would be the same subnet in both files it would not be merged:

  default:
    name: apache_default
    driver: bridge
    ipam:
      config:
        - subnet: 172.22.0.0/29
        - subnet: 172.22.0.0/29

leading to a more bizarre error:

 ✘ Network apache_default  Error                                                                                                                                  0.0s 
failed to create network apache_default: Error response from daemon: Pool overlaps with other one on this address space

[ndeloof]

I don't get the logic here. Why only merge the first element ?
IIUC we should merge IPAM configs within the same network segment (same subnet) and append the others

[glours]

Rohh my bad 🤦

[glours]

I'll fix that Monday 😞

[ndeloof]

tes should include another subnet which should be kept unchanged, + another that should be appended, so we cover all use-cases

[milas]

LGTM besides the already-commented on IPAM merge behavior