Fixed: Use Array.Empty and fix a few multiple enumerations

(cherry picked from commit 11d91faaada0e70910c832ce405ddeed52a24172)

src/NzbDrone.Common/Composition/AssemblyLoader.cs

@@ -5,8 +5,6 @@ using System.Linq;
 using System.Reflection;
 using System.Runtime.InteropServices;
 using System.Runtime.Loader;
-using System.Text;
-using System.Threading.Tasks;
 using NzbDrone.Common.EnvironmentInfo;
 
 namespace NzbDrone.Common.Composition
@@ -19,16 +17,17 @@ namespace NzbDrone.Common.Composition
             RegisterSQLiteResolver();
         }
 
-        public static IEnumerable<Assembly> Load(IEnumerable<string> assemblies)
+        public static IList<Assembly> Load(IList<string> assemblyNames)
         {
-            var toLoad = assemblies.ToList();
+            var toLoad = assemblyNames.ToList();
             toLoad.Add("Prowlarr.Common");
             toLoad.Add(OsInfo.IsWindows ? "Prowlarr.Windows" : "Prowlarr.Mono");
 
             var startupPath = AppDomain.CurrentDomain.BaseDirectory;
 
-            return toLoad.Select(x =>
+            return toLoad
-                AssemblyLoadContext.Default.LoadFromAssemblyPath(Path.Combine(startupPath, $"{x}.dll")));
+                .Select(x => AssemblyLoadContext.Default.LoadFromAssemblyPath(Path.Combine(startupPath, $"{x}.dll")))
+                .ToList();
         }
 
         private static Assembly ContainerResolveEventHandler(object sender, ResolveEventArgs args)

src/NzbDrone.Common/OAuth/WebParameterCollection.cs

@@ -14,14 +14,14 @@ namespace NzbDrone.Common.OAuth
         {
             get
             {
-                var parameters = this.Where(p => p.Name.Equals(name));
+                var parameters = this.Where(p => p.Name.Equals(name)).ToArray();
 
                 if (!parameters.Any())
                 {
                     return null;
                 }
 
-                if (parameters.Count() == 1)
+                if (parameters.Length == 1)
                 {
                     return parameters.Single();
                 }

src/NzbDrone.Core/Datastore/BasicRepository.cs

@@ -103,7 +103,7 @@ namespace NzbDrone.Core.Datastore
         {
             if (!ids.Any())
             {
-                return new List<TModel>();
+                return Array.Empty<TModel>();
             }
 
             var result = Query(x => ids.Contains(x.Id));

src/NzbDrone.Core/Download/Clients/DownloadStation/Proxies/DownloadStationTaskProxy.cs

@@ -1,3 +1,4 @@
+using System;
 using System.Collections.Generic;
 using System.Net.Http;
 using NLog;
@@ -64,7 +65,7 @@ namespace NzbDrone.Core.Download.Clients.DownloadStation.Proxies
             catch (DownloadClientException e)
             {
                 _logger.Error(e);
-                return new List<DownloadStationTask>();
+                return Array.Empty<DownloadStationTask>();
             }
         }
 

src/NzbDrone.Core/IndexerSearch/NewznabResults.cs

@@ -22,7 +22,7 @@ namespace NzbDrone.Core.IndexerSearch
             @"(?<![\uD800-\uDBFF])[\uDC00-\uDFFF]|[\uD800-\uDBFF](?![\uDC00-\uDFFF])|[\x00-\x08\x0B\x0C\x0E-\x1F\x7F-\x9F\uFEFF\uFFFE\uFFFF]",
             RegexOptions.Compiled);
 
-        public List<ReleaseInfo> Releases { get; set; }
+        public IList<ReleaseInfo> Releases { get; set; }
 
         private static string RemoveInvalidXMLChars(string text)
         {

src/NzbDrone.Core/IndexerSearch/ReleaseSearchService.cs

@@ -148,7 +148,7 @@ namespace NzbDrone.Core.IndexerSearch
             return spec;
         }
 
-        private async Task<List<ReleaseInfo>> Dispatch(Func<IIndexer, Task<IndexerPageableQueryResult>> searchAction, SearchCriteriaBase criteriaBase)
+        private async Task<IList<ReleaseInfo>> Dispatch(Func<IIndexer, Task<IndexerPageableQueryResult>> searchAction, SearchCriteriaBase criteriaBase)
         {
             var indexers = _indexerFactory.Enabled();
 
@@ -168,7 +168,7 @@ namespace NzbDrone.Core.IndexerSearch
                 if (indexers.Count == 0)
                 {
                     _logger.Debug("All provided categories are unsupported by selected indexers: {0}", string.Join(", ", criteriaBase.Categories));
-                    return new List<ReleaseInfo>();
+                    return Array.Empty<ReleaseInfo>();
                 }
             }
 
@@ -189,7 +189,7 @@ namespace NzbDrone.Core.IndexerSearch
         {
             if (_indexerLimitService.AtQueryLimit((IndexerDefinition)indexer.Definition))
             {
-                return new List<ReleaseInfo>();
+                return Array.Empty<ReleaseInfo>();
             }
 
             try
@@ -224,7 +224,7 @@ namespace NzbDrone.Core.IndexerSearch
                 _logger.Error(e, "Error while searching for {0}", criteriaBase);
             }
 
-            return new List<ReleaseInfo>();
+            return Array.Empty<ReleaseInfo>();
         }
     }
 }

src/NzbDrone.Core/Indexers/IndexerCapabilitiesCategories.cs

@@ -93,7 +93,7 @@ namespace NzbDrone.Core.Indexers
         {
             if (string.IsNullOrWhiteSpace(input))
             {
-                return new List<IndexerCategory>();
+                return Array.Empty<IndexerCategory>();
             }
 
             var cats = _categoryMapping
@@ -109,7 +109,7 @@ namespace NzbDrone.Core.Indexers
         {
             if (string.IsNullOrWhiteSpace(trackerCategoryDesc))
             {
-                return new List<IndexerCategory>();
+                return Array.Empty<IndexerCategory>();
             }
 
             var cats = _categoryMapping

src/NzbDrone.Core/Indexers/IndexerFactory.cs

@@ -189,7 +189,7 @@ namespace NzbDrone.Core.Indexers
 
         public override IEnumerable<IndexerDefinition> GetPresetDefinitions(IndexerDefinition providerDefinition)
         {
-            return new List<IndexerDefinition>();
+            return Array.Empty<IndexerDefinition>();
         }
 
         public override void SetProviderCharacteristics(IIndexer provider, IndexerDefinition definition)

src/NzbDrone.Core/Indexers/RssParser.cs

@@ -82,7 +82,12 @@ namespace NzbDrone.Core.Indexers
                 }
             }
 
-            return !PostProcess(indexerResponse, items, releases) ? new List<ReleaseInfo>() : releases;
+            if (!PostProcess(indexerResponse, items, releases))
+            {
+                return Array.Empty<ReleaseInfo>();
+            }
+
+            return releases;
         }
 
         public Action<IDictionary<string, string>, DateTime?> CookiesUpdater { get; set; }

src/Prowlarr.Api.V1/ProviderControllerBase.cs

@@ -44,11 +44,11 @@ namespace Prowlarr.Api.V1
         [Produces("application/json")]
         public List<TProviderResource> GetAll()
         {
-            var providerDefinitions = _providerFactory.All().OrderBy(p => p.ImplementationName);
+            var providerDefinitions = _providerFactory.All();
 
-            var result = new List<TProviderResource>(providerDefinitions.Count());
+            var result = new List<TProviderResource>(providerDefinitions.Count);
 
-            foreach (var definition in providerDefinitions)
+            foreach (var definition in providerDefinitions.OrderBy(p => p.ImplementationName))
             {
                 _providerFactory.SetProviderCharacteristics(definition);
 

src/Prowlarr.Http/REST/RestController.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using System.Reflection;
 using FluentValidation;
 using FluentValidation.Results;
 using Microsoft.AspNetCore.Mvc;
@@ -73,7 +74,8 @@ namespace Prowlarr.Http.REST
                 }
             }
 
-            var attributes = descriptor.MethodInfo.CustomAttributes;
+            var attributes = descriptor.MethodInfo.CustomAttributes as IReadOnlyCollection<CustomAttributeData> ??
+                             descriptor.MethodInfo.CustomAttributes.ToArray();
             if (attributes.Any(x => VALIDATE_ID_ATTRIBUTES.Contains(x.AttributeType)) && !skipValidate)
             {
                 if (context.ActionArguments.TryGetValue("id", out var idObj))