Null Ports property on ListContainersAsync

[DJREMiX6]

Hi, I found that some containers returned by ListContainersAsync may have a null Ports property instead of returning an empty IList.

Code Example

// DockerClient injected via DI
var dockerContainers = await _dockerClient.Containers.ListContainersAsync(
    new ContainersListParameters { All = true }, cancellationToken);

foreach(var dockerContainer in dockerContainers)
{
    // Ports property may be null
    var ports = dockerContainer.Ports;
}

Inspected Example

In this example you can see the informations related to a container that actuallly has null Ports property.

System Info

Result of dotnet --info:

.NET SDK:
 Version:           10.0.201
 Commit:            4d3023de60
 Workload version:  10.0.200-manifests.121cc9e6
 MSBuild version:   18.3.0-release-26153-122+4d3023de6

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.26200
 OS Platform: Windows
 RID:         win-x64
 Base Path:   C:\Program Files\dotnet\sdk\10.0.201\

.NET workloads installed:
There are no installed workloads to display.
Configured to use workload sets when installing new manifests.
No workload sets are installed. Run "dotnet workload restore" to install a workload set.

Host:
  Version:      10.0.5
  Architecture: x64
  Commit:       a612c2a105

.NET SDKs installed:
  10.0.201 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
  Microsoft.AspNetCore.App 10.0.5 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 6.0.36 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 8.0.22 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 10.0.5 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.WindowsDesktop.App 6.0.36 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 10.0.5 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

Other architectures found:
  x86   [C:\Program Files (x86)\dotnet]
    registered at [HKLM\SOFTWARE\dotnet\Setup\InstalledVersions\x86\InstallLocation]

Environment variables:
  DOTNET_CLI_UI_LANGUAGE                   [en-US]
  DOTNET_GCHeapCount                       [2]
  DOTNET_GCNoAffinitize                    [1]
  DOTNET_MULTILEVEL_LOOKUP                 [0]
  DOTNET_TC_CallCountThreshold             [1000]
  DOTNET_ThreadPool_UnfairSemaphoreSpinLimit [0]
  DOTNET_gcConcurrent                      [0]
  Detected COMPlus_* environment variable(s). Consider transitioning to DOTNET_* equivalent.

global.json file:
  Not found

Learn more:
  https://aka.ms/dotnet/info

Download .NET:
  https://aka.ms/dotnet/download

Docker.DotNet Version:
3.125.15

[HofmeisterAn]

Thanks for creating the issue. You're referring to that the property is not marked as nullable?

Docker.DotNet/src/Docker.DotNet/Models/ContainerListResponse.Generated.cs

Lines 27 to 28 in c0f44a7

	[JsonPropertyName("Ports")]
	public IList<Port> Ports { get; set; }

I think this repo does not properly implement nullability.

We started adding support for it in our forked version (https://github.com/testcontainers/Docker.DotNet), along with many refactorings and improvements. Nullable support for the generated model classes isn't there yet though. But good point, I'll create an issue in the forked repo for that.

[DJREMiX6]

You're referring to that the property is not marked as nullable?

Hi, yes the Ports property is defined as an IList and does not support nullability, that said, as you can see in the image on the issue, the Port property sometimes results in a null value (I don't understand the cases), sincerely I do not expect it to be nullable but instead return an empty IList if not port is found on the container.

[HofmeisterAn]

The response comes from the Docker Engine. I don't think they document nullability. In general, I'd treat fields marked with omitempty as nullable, even though the Ports field isn't marked that way. Maybe collections are nullable by default too. In the forked version, I try to be more explicit about what's nullable.