ArgumentNullException for autocompleteUrl using Azure Artifacts feed

When using NuGetClient with an Azure Artifacts feed, calling GetPackageMetadataAsync throws an ArgumentNullException for autocompleteUrl.

To Reproduce

1. Create a public Azure Artifacts NuGet feed. I have an empty one at https://pkgs.dev.azure.com/mysqlnet/MySqlConnector/_packaging/test/nuget/v3/index.json
2. Install BaGet.Protocol 0.3.0-preview2
3. Run this code:

var client = new NuGetClient("https://pkgs.dev.azure.com/mysqlnet/MySqlConnector/_packaging/test/nuget/v3/index.json");
await client.GetPackageMetadataAsync("Test");

1. There’s an unhandled exception:

ArgumentNullException: Value cannot be null. (Parameter 'autocompleteUrl')
   at BaGet.Protocol.Internal.RawSearchClient..ctor(HttpClient httpClient, String searchUrl, String autocompleteUrl) in D:\a\1\s\src\BaGet.Protocol\Search\RawSearchClient.cs:line 33
   at BaGet.Protocol.NuGetClientFactory.GetAsync[T](Func`2 clientFactory, CancellationToken cancellationToken) in D:\a\1\s\src\BaGet.Protocol\NuGetClientFactory.cs:line 151
   at BaGet.Protocol.NuGetClientFactory.PackageMetadataClient.GetRegistrationIndexOrNullAsync(String packageId, CancellationToken cancellationToken) in D:\a\1\s\src\BaGet.Protocol\PackageMetadata\PackageMetadataClient.cs:line 24
   at BaGet.Protocol.NuGetClient.GetPackageMetadataAsync(String packageId, CancellationToken cancellationToken) in D:\a\1\s\src\BaGet.Protocol\NuGetClient.cs:line 200

Expected behavior

That BaGet.Protocol should be able to retrieve package metadata from Azure Artifacts, even if all NuGet API v3 services aren’t exposed.

[bgrainger]

Confirmed that preview3 works great; thanks!

[loic-sharma]

Thanks for reporting! I’ll do two fixes:

1. The autocomplete resource isn’t required (see this), BaGet.Protocol shouldn’t assume it exists
2. BaGet.Protocol should throw a better exception if it cannot find an expected resource