Docker Compose Service Configuration Merging

We cannot reset network_mode in an override compose file.

Docker compose does not allow you to unset a previously set field like network_mode. If you specify network_mode: host in one Compose file, there is no way in another Compose file to reset it back to the default (bridge) or remove it entirely.

Setting network_mode: none disables networking for the container, which is not what we want either.
If you set a field in the base file (like network_mode: host), the override file can only replace it with another value.

There is no way to unset a field; i.e. it can only be replaced or left as-is.

Solution:

Original Compose files

`compose.yml`	compose-expose-port.yml
```yml services: app: build: . environment: PORT: 3000 network_mode: host ```	```yml services: app: build: . ports: - 3000:3000 ```

Remove network_mode: host from the default Compose file:

services:
  app:
    build: .
    environment:
      PORT: 3000
  ports:
    - 3000:3000

Create separate Compose files for network_mode: host, e.g. compose-host.yml:
```
services:
  app:
    network_mode: host
```
Then you can merge them like this: docker compose -f compose.yml -f compose-host.yml up --build -d.

Or you can use docker compose up --build -d to create a network and expose the ports.

[!NOTE]

We do not care about the ports in the default compose file when we merge it with the compose-host.yml since it will be discarded by Docker. And if we run it on its own it will export the port as it should. So in short we flipped the script by changing how networking is handled.