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openedon Feb 18, 2024
Our server returns HTTP 304 (Not Modified) without a response body when the incoming fingerprint in the If-None-Match header matches the stored version. This enables clients to poll for changes without receiving a response body, unless it has changed since it was last fetched.
Status 304 is described in the OAS document, but Kiota throws an ApiException saying the error isn't mapped:
Microsoft.Kiota.Abstractions.ApiException: The server returned an unexpected status code and no error factory is registered for this code: 304
OAS fragment:
{
"paths": {
"/api/people": {
"get": {
"tags": [
"people"
],
"summary": "Retrieves a collection of people.",
"operationId": "getPersonCollection",
"responses": {
"200": {
"description": "Successfully returns the found people, or an empty array if none were found.",
"headers": {
"ETag": {
"description": "A fingerprint of the HTTP response, which can be used in an If-None-Match header to only fetch changes.",
"required": true,
"schema": {
"type": "string"
}
}
},
"content": {
"application/vnd.api+json": {
"schema": {
"$ref": "#/components/schemas/personCollectionResponseDocument"
}
}
}
},
"400": {
"description": "The query string is invalid.",
"content": {
"application/vnd.api+json": {
"schema": {
"$ref": "#/components/schemas/errorResponseDocument"
}
}
}
},
"304": {
"description": "The fingerprint of the HTTP response matches one of the ETags from the incoming If_None_Match header.",
"headers": {
"ETag": {
"description": "A fingerprint of the HTTP response, which can be used in an If-None-Match header to only fetch changes.",
"required": true,
"schema": {
"type": "string"
}
}
}
}
}
}
}
}
}Generated C# code:
namespace GeneratedClient.Api.People {
public class PeopleRequestBuilder : BaseRequestBuilder {
/// <summary>
/// Retrieves a collection of people.
/// </summary>
/// <param name="cancellationToken">Cancellation token to use when cancelling requests</param>
/// <param name="requestConfiguration">Configuration for the request such as headers, query parameters, and middleware options.</param>
#if NETSTANDARD2_1_OR_GREATER || NETCOREAPP3_1_OR_GREATER
#nullable enable
public async Task<PersonCollectionResponseDocument?> GetAsync(Action<RequestConfiguration<PeopleRequestBuilderGetQueryParameters>>? requestConfiguration = default, CancellationToken cancellationToken = default) {
#nullable restore
#else
public async Task<PersonCollectionResponseDocument> GetAsync(Action<RequestConfiguration<PeopleRequestBuilderGetQueryParameters>> requestConfiguration = default, CancellationToken cancellationToken = default) {
#endif
var requestInfo = ToGetRequestInformation(requestConfiguration);
var errorMapping = new Dictionary<string, ParsableFactory<IParsable>> {
{"400", ErrorResponseDocument.CreateFromDiscriminatorValue},
};
return await RequestAdapter.SendAsync<PersonCollectionResponseDocument>(requestInfo, PersonCollectionResponseDocument.CreateFromDiscriminatorValue, errorMapping, cancellationToken).ConfigureAwait(false);
}
}
}To work around this, we need to catch an exception to detect HTTP 304 is being returned:
var headerInspector = new HeadersInspectionHandlerOption
{
InspectResponseHeaders = true
};
PersonCollectionResponseDocument? getResponse1 = await client.Api.People.GetAsync(
configuration => configuration.Options.Add(headerInspector));
string eTag = headerInspector.ResponseHeaders["ETag"].Single();
try
{
PersonCollectionResponseDocument? getResponse2 = await client.Api.People.GetAsync(
configuration => configuration.Headers.Add("If-None-Match", eTag));
}
catch (ApiException exception) when (exception.ResponseStatusCode == (int)HttpStatusCode.NotModified)
{
Console.WriteLine("The HTTP response hasn't changed, so no response body was returned.");
}This looks like a bug to me. In KiotaBuilder.cs, I found the following line:
private static readonly HashSet<string> noContentStatusCodes = new(StringComparer.OrdinalIgnoreCase) { "201", "202", "204", "205" };Should that just be changed to include 304?
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