[BUG] [csharp] DefaultExceptionFactory hides exceptions

[chrbkr]

The openapi-generator creates this ExceptionFactory:

openapi-generator/samples/client/petstore/csharp/OpenAPIClientNetStandard/src/Org.OpenAPITools/Client/Configuration.cs

Lines 48 to 62 in 150e24d

	/// <summary>
	/// Default creation of exceptions for a given method name and response object
	/// </summary>
	public static readonly ExceptionFactory DefaultExceptionFactory = (methodName, response) =>
	{
	var status = (int)response.StatusCode;
	if (status >= 400)
	{
	return new ApiException(status,
	string.Format("Error calling {0}: {1}", methodName, response.Content),
	response.Content);
	}
	return null;
	};

First of all, I'm not sure handling response codes as exceptions is good practice, but that could be debated.

However, what's much worse is that real exceptions are hidden - in case a timeout occurs, or the connection is closed etc., all I get is a null response instead of the real exception.

Am I missing something? How are other people handling this?

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[mbrookson]

Found a similar issue with this, where an API returned a 401 auth error but the generated client hides the exception. Only found the real result by stepping through with the debugger.

[Eugeny]

Exception handling in the csharp generator is simply broken. The only error type that is bubbled up are 400+ HTTP codes. Moreover, there's no way to override it except for setting a new exception handler manually on every *Api instance.

[Eugeny]

And there's no way to universally construct an *Api instance because they don't have a common ancestor with a new(Configuration) constructor

[valmoz]

We received a null result when contacting our APIs due to this RestSharp issue. It was a real pain to debug.

To avoid receiving a Null result we decided to declare a custom ExceptionFactory to overcome this issue. I think it would be better to include something similar to the template to be able to manage errors unrelated to the API.

apiInstance.ExceptionFactory = (methodName, response) =>
            {
                var status = (int)response.StatusCode;
                if (status >= 400)
                {
                    return new ApiException(status,
                        string.Format("Error calling {0}: {1}", methodName, response.RawContent),
                        response.RawContent, response.Headers);
                }
                return new Exception(string.Format("Generic error: {0}", response.ErrorText));
            };

[kipusoep]

Well I had a similar issue, where I was expecting a 400 Bad Request and that's what I wanted to check in Specflow, but the response was eaten by the ApiException.
So now I override the ExceptionFactory, but this could be greatly improved I think.

[MichaelMay81]

There seems to be a bugfix for netStandard as described in #15471, but not in general use. This fix creates an ApiException for status code 0.
To me that seems a better solution for error handling, than to generate a general exception to all responses. This still hides non error related responses, but I don't think exceptions are the right place for those any way.

[ryanwilliams83]

What if we modify the instance of RestSharp ClientOptions being created at

openapi-generator/modules/openapi-generator/src/main/resources/csharp/ApiClient.mustache

Line 463 in bc70f04

var clientOptions = new RestClientOptions(baseUrl)

to expose the ThrowOnAnyError property to allow people to use the native RestSharp error handling functionality which does not have this problem?

💡If the RestSharp client throws an exception before the OpenApi client attempts to inspect the response, then we don't need to fix the bug in the OpenApi client error handling.

https://restsharp.dev/docs/advanced/error-handling/

[ryanwilliams83]

@valmoz valmoz, you might find that your custom ExceptionFactory does not behave correctly when the client is unable to establish a connection to the remote host.
In my experience the .StatusCode will be 0 when the client has a DNS Lookup Failure or TCP connection problem.

To test for yourself, configure your BasePath to a host that does not exist and see what happens.