Preserve service network aliases and healthcheck in generated Compose output

[Copilot]

docker-autocompose was collapsing service network attachments to name-only output, dropping per-network attributes like Aliases, and it was not serializing Config.Healthcheck. This change keeps service-level network details from docker inspect and maps healthcheck fields into Compose-compatible output while preserving existing default-network behavior.

• Service network attachment fidelity

  • Read NetworkSettings.Networks as structured per-network config instead of a set of names.
  • Preserve Aliases per network.
  • Emit service networks: as:
    • mapping form when per-network config exists (e.g., aliases),
    • list form for simple network-only attachments.

• Top-level network declarations

  • Keep existing top-level networks generation unchanged.
  • Ensure service-level services.<name>.networks and top-level networks coexist correctly.

• Healthcheck serialization

  • Add mapping from inspect healthcheck to Compose:
    • Test → test
    • Interval → interval
    • Timeout → timeout
    • Retries → retries
    • StartPeriod → start_period
  • Normalize integer duration values into Compose-friendly duration strings (<ns>ns).

• Regression coverage

  • Add focused tests for:
    • alias preservation in service-level network config,
    • healthcheck preservation,
    • simple custom-network list-form behavior,
    • unchanged default-network (network_mode) behavior.

services:
  svc:
    networks:
      custom_net:
        aliases:
          - svc
          - db
    healthcheck:
      test: ["CMD-SHELL", "echo ok"]
      interval: "1000000000ns"
      timeout: "2000000000ns"
      retries: 3
      start_period: "3000000000ns"

networks:
  custom_net:
    external: true
    name: custom_net

Original prompt

Implement a fix for issue #89 in Red5d/docker-autocompose.

Context:

• Repository: Red5d/docker-autocompose
• Issue: https://github.com/Red5d/docker-autocompose/issues/89
• Relevant comment: https://github.com/Red5d/docker-autocompose/issues/89#issuecomment-4645166865

Observed problem:

• The tool currently drops service-level Docker network attachment details when reconstructing Compose output from docker inspect data.
• In particular, NetworkSettings.Networks.<network>.Aliases is not preserved.
• The tool also appears to omit Config.Healthcheck entirely.

Current implementation details:

• In src/autocompose.py, service networks are currently collapsed into a set of network names, which loses nested per-network attributes like aliases.
• Top-level network definitions are generated separately, but service-level networks: output cannot currently express mapping-form network configuration.
• There is no serialization path for Config.Healthcheck into Compose healthcheck: output.

Required changes:

1. Preserve service-level network attachment configuration from docker inspect.
   • Read cattrs["NetworkSettings"]["Networks"].
   • Preserve per-network aliases at minimum.
   • Emit service networks: in Compose-compatible form:
     • use mapping form when per-network options exist
     • otherwise keep valid minimal output for simple cases
2. Keep top-level network definitions working.
   • Do not break the existing generation of top-level networks: entries.
   • Ensure service-level network config and top-level network declarations coexist correctly.
3. Add healthcheck serialization.
   • Read cattrs["Config"]["Healthcheck"].
   • Map Docker inspect fields to Compose healthcheck keys:
     • Test -> test
     • Interval -> interval
     • Timeout -> timeout
     • Retries -> retries
     • StartPeriod -> start_period
   • Convert Docker duration values to Compose-friendly duration strings if needed.
4. Add or update tests to cover the regression.
   • aliases are preserved in service network config
   • healthcheck is preserved
   • simple network-only cases still work
   • existing behavior for default networks remains intact where appropriate

Implementation guidance:

• Favor preserving aliases exactly as returned by inspect for the initial fix rather than filtering them aggressively.
• Keep the patch focused on issue lost aliases #89.
• Update tests and any fixtures as needed.

Deliverable:

• Open a pull request against master implementing the above fixes with a concise PR title and description.

The following is the prior conversation context from the user's chat exploration (may be truncated):

User: Try and figure out what the actual issue is here and what should be done to fix it.

Assistant: The actual issue is not just “aliases are lost” — it’s that docker-autocompose currently reconstructs only a very shallow subset of network and container config, so it drops per-network service details like aliases, and it also omits healthcheck. The code is reading the raw Docker inspect data, but it never maps those fields into Compose output.

Specifically:

• For networks, the tool currently stores only the set of network names for the service, not the per-network config object. In src/autocompose.py, values["networks"] is built as a set of network names from NetworkSettings.Networks.keys(). That means fields under each network like Aliases, IPv4Address, etc. are discarded immediately. Later it only emits top-level network definitions like external and name, not service-level network attachments. So aliases cannot survive with the current data model.
• For health checks, there appears to be no code path at all that reads Config.Healthcheck and converts it into Compose healthcheck: output.
• The user’s example confirms this: Docker inspect shows aliases under NetworkSettings.Networks.<network>.Aliases, and healthcheck under Config.Healthcheck, but the generator never serializes either of those into the compose structure.

The key code causing the network-loss problem is here:

"networks": {
    x for x in cattrs.get("NetworkSettings", {}).get("Networks", {}).keys() if x not in default_networks
},
...
else:
    networklist = c.networks.list()
    for network in networklist:
        if network.attrs["Name"] in values["networks"]:
            networks[network.attrs["Name"]] = {
                "external": (not network.attrs["Internal"]),
                "name": network.attrs["Name"],
            }

What the bug really is

docker-autocompose is treating:

• top-level Compose networks
• and service-level network attachments

as if they were the same thing.

But in Compose they are different:

• top-level networks: defines the network objects
• service-leve...

This pull request was created from Copilot chat.