Disposable interfaces

[trejjam]

What kind of change does this PR introduce?
Feature, resolve #660. A generated client has an implementation of IDisposable.Dispose (if interface is marked as IDisposable)

What is the current behavior?
IDispose is not generated, when necessary.

What is the new behavior?
Interface marked with IDisposable has implemented IDispose method

void IDisposable.Dispose()
{
    Client?.Dispose();
}

What might this PR break?
Nothing

Please check if the PR fulfills these requirements

• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

Other information:
This feature is handling following messages when AddRefitClient is used for registration (HttpClient is created using IHttpClientFactory)

[15:18:02 DBG] Microsoft.Extensions.Http.DefaultHttpClientFactory
        HttpMessageHandler expired after 120000ms for client '...'
[15:18:12 DBG] Microsoft.Extensions.Http.DefaultHttpClientFactory
        Starting HttpMessageHandler cleanup cycle with 2 items
[15:18:12 DBG] Microsoft.Extensions.Http.DefaultHttpClientFactory
        Ending HttpMessageHandler cleanup cycle after 0.6748ms - processed: 0 items - remaining: 2 items

[bennor]

Weirdly, HttpClient is not supposed to be disposed. From the official docs:

HttpClient is intended to be instantiated once and re-used throughout the life of an application. Instantiating an HttpClient class for every request will exhaust the number of sockets available under heavy loads. This will result in SocketException errors.

[trejjam]

Hi, yes the default (empty) constructor should not. HttpClient created through HttpClientFactory has shorter lifetime with different internal behaviour.

[iansteed]

@trejjam is correct, a generated client is injected with a new HttpClient instance each time it's created. The instance contains client specific base address, timeout, headers, and pipeline handlers. The underlying HttpMessageHandler is performing the actual requests and is managed by the HttpClientFactory.

https://docs.microsoft.com/en-us/dotnet/architecture/microservices/implement-resilient-applications/use-httpclientfactory-to-implement-resilient-http-requests

Use IHttpClientFactory to implement resilient HTTP requests

Learn how to use IHttpClientFactory, available since .NET Core 2.1, for creating `HttpClient` instances, making it easy for you to use it in your applications.

[bennor]

Looks like I have some reading to do. 😳

[github-actions]

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