[Client SDK] Make the autocomplete resource optional (#481)

Addresses #477

src/BaGet.Protocol/Extensions/ServiceIndexModelExtensions.cs

@@ -1,3 +1,4 @@
+using System;
 using System.Linq;
 using BaGet.Protocol.Models;
 
@@ -33,22 +34,22 @@ public static class ServiceIndexModelExtensions
 
         public static string GetPackageContentResourceUrl(this ServiceIndexResponse serviceIndex)
         {
-            return serviceIndex.GetResourceUrl(PackageBaseAddress);
+            return serviceIndex.GetRequiredResourceUrl(PackageBaseAddress, nameof(PackageBaseAddress));
         }
 
         public static string GetPackageMetadataResourceUrl(this ServiceIndexResponse serviceIndex)
         {
-            return serviceIndex.GetResourceUrl(RegistrationsBaseUrl);
+            return serviceIndex.GetRequiredResourceUrl(RegistrationsBaseUrl, nameof(RegistrationsBaseUrl));
         }
 
-        public static string GetCatalogResourceUrl(this ServiceIndexResponse serviceIndex)
+        public static string GetSearchQueryResourceUrl(this ServiceIndexResponse serviceIndex)
         {
-            return serviceIndex.GetResourceUrl(Catalog);
+            return serviceIndex.GetRequiredResourceUrl(SearchQueryService, nameof(SearchQueryService));
         }
 
-        public static string GetSearchQueryResourceUrl(this ServiceIndexResponse serviceIndex)
+        public static string GetCatalogResourceUrl(this ServiceIndexResponse serviceIndex)
         {
-            return serviceIndex.GetResourceUrl(SearchQueryService);
+            return serviceIndex.GetResourceUrl(Catalog);
         }
 
         public static string GetSearchAutocompleteResourceUrl(this ServiceIndexResponse serviceIndex)
@@ -62,5 +63,19 @@ public static string GetResourceUrl(this ServiceIndexResponse serviceIndex, stri
 
             return resource?.ResourceUrl.Trim('/');
         }
+
+        public static string GetRequiredResourceUrl(this ServiceIndexResponse serviceIndex, string[] types, string resourceName)
+        {
+            // For more information on required resources,
+            // see: https://docs.microsoft.com/en-us/nuget/api/overview#resources-and-schema
+            var resourceUrl = serviceIndex.GetResourceUrl(types);
+            if (string.IsNullOrEmpty(resourceUrl))
+            {
+                throw new InvalidOperationException(
+                    $"The service index does not have a resource named '{resourceName}'");
+            }
+
+            return resourceUrl;
+        }
     }
 }

src/BaGet.Protocol/NuGetClientFactory.cs

@@ -162,13 +162,18 @@ private async Task<T> GetAsync<T>(Func<NuGetClients, T> clientFactory, Cancellat
                         var searchResourceUrl = serviceIndex.GetSearchQueryResourceUrl();
                         var autocompleteResourceUrl = serviceIndex.GetSearchAutocompleteResourceUrl();
 
+                        // Create clients for requires resources.
                         var contentClient = new RawPackageContentClient(_httpClient, contentResourceUrl);
                         var metadataClient = new RawPackageMetadataClient(_httpClient, metadataResourceUrl);
                         var searchClient = new RawSearchClient(_httpClient, searchResourceUrl);
-                        var autocompleteClient = new RawAutocompleteClient(_httpClient, autocompleteResourceUrl);
+
+                        // Create clients for optional resources.
                         var catalogClient = catalogResourceUrl == null
                             ? new NullCatalogClient() as ICatalogClient
                             : new RawCatalogClient(_httpClient, catalogResourceUrl);
+                        var autocompleteClient = autocompleteResourceUrl == null
+                            ? new NullAutocompleteClient() as IAutocompleteClient
+                            : new RawAutocompleteClient(_httpClient, autocompleteResourceUrl);
 
                         _clients = new NuGetClients
                         {

src/BaGet.Protocol/Search/NullAutocompleteClient.cs

@@ -0,0 +1,28 @@
+using System.Collections.Generic;
+using System.Threading;
+using System.Threading.Tasks;
+using BaGet.Protocol.Models;
+
+namespace BaGet.Protocol.Internal
+{
+    public class NullAutocompleteClient : IAutocompleteClient
+    {
+        public Task<AutocompleteResponse> AutocompleteAsync(string query = null, int skip = 0, int take = 20, bool includePrerelease = true, bool includeSemVer2 = true, CancellationToken cancellationToken = default)
+        {
+            return Task.FromResult(new AutocompleteResponse
+            {
+                TotalHits = 0,
+                Data = new List<string>()
+            });
+        }
+
+        public Task<AutocompleteResponse> ListPackageVersionsAsync(string packageId, bool includePrerelease = true, bool includeSemVer2 = true, CancellationToken cancellationToken = default)
+        {
+            return Task.FromResult(new AutocompleteResponse
+            {
+                TotalHits = 0,
+                Data = new List<string>()
+            });
+        }
+    }
+}