Use Array.Empty and fix a few multiple enumerations

(cherry picked from commit 11d91faaada0e70910c832ce405ddeed52a24172)

Closes #3451

src/Lidarr.Api.V1/ProviderControllerBase.cs

@@ -43,11 +43,11 @@ namespace Lidarr.Api.V1
         [HttpGet]
         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/Lidarr.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 Lidarr.Http.REST.Attributes;
@@ -67,7 +68,8 @@ namespace Lidarr.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))

src/NzbDrone.Common/Composition/AssemblyLoader.cs

@@ -17,16 +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("Lidarr.Common");
             toLoad.Add(OsInfo.IsWindows ? "Lidarr.Windows" : "Lidarr.Mono");
 
             var startupPath = AppDomain.CurrentDomain.BaseDirectory;
 
-            return toLoad.Select(x =>
-                AssemblyLoadContext.Default.LoadFromAssemblyPath(Path.Combine(startupPath, $"{x}.dll")));
+            return toLoad
+                .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

@@ -111,7 +111,7 @@ 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/DownloadStationTaskProxyV1.cs

@@ -1,3 +1,4 @@
+using System;
 using System.Collections.Generic;
 using System.Net.Http;
 using NLog;
@@ -61,7 +62,7 @@ namespace NzbDrone.Core.Download.Clients.DownloadStation.Proxies
             catch (DownloadClientException e)
             {
                 _logger.Error(e);
-                return new List<DownloadStationTask>();
+                return Array.Empty<DownloadStationTask>();
             }
         }
 

src/NzbDrone.Core/Download/Clients/DownloadStation/Proxies/DownloadStationTaskProxyV2.cs

@@ -1,3 +1,4 @@
+using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Net.Http;
@@ -135,7 +136,7 @@ namespace NzbDrone.Core.Download.Clients.DownloadStation.Proxies
             catch (DownloadClientException e)
             {
                 _logger.Error(e);
-                return new List<DownloadStationTask>();
+                return Array.Empty<DownloadStationTask>();
             }
         }
 

src/NzbDrone.Core/Extras/Metadata/MetadataService.cs

@@ -145,7 +145,7 @@ namespace NzbDrone.Core.Extras.Metadata
 
             if (artistFolder.IsNullOrWhiteSpace() && albumFolder.IsNullOrWhiteSpace())
             {
-                return new List<MetadataFile>();
+                return Array.Empty<MetadataFile>();
             }
 
             var files = new List<MetadataFile>();

src/NzbDrone.Core/Indexers/HttpIndexerBase.cs

@@ -42,7 +42,7 @@ namespace NzbDrone.Core.Indexers
         {
             if (!SupportsRss)
             {
-                return new List<ReleaseInfo>();
+                return Array.Empty<ReleaseInfo>();
             }
 
             return FetchReleases(g => g.GetRecentRequests(), true);
@@ -52,7 +52,7 @@ namespace NzbDrone.Core.Indexers
         {
             if (!SupportsSearch)
             {
-                return new List<ReleaseInfo>();
+                return Array.Empty<ReleaseInfo>();
             }
 
             return FetchReleases(g => g.GetSearchRequests(searchCriteria));
@@ -62,7 +62,7 @@ namespace NzbDrone.Core.Indexers
         {
             if (!SupportsSearch)
             {
-                return new List<ReleaseInfo>();
+                return Array.Empty<ReleaseInfo>();
             }
 
             return FetchReleases(g => g.GetSearchRequests(searchCriteria));

src/NzbDrone.Core/Indexers/RssParser.cs

@@ -85,7 +85,7 @@ namespace NzbDrone.Core.Indexers
 
             if (!PostProcess(indexerResponse, items, releases))
             {
-                return new List<ReleaseInfo>();
+                return Array.Empty<ReleaseInfo>();
             }
 
             return releases;

src/NzbDrone.Core/MediaFiles/TrackImport/ImportApprovedTracks.cs

@@ -128,11 +128,12 @@ namespace NzbDrone.Core.MediaFiles.TrackImport
                 _eventAggregator.PublishEvent(new AlbumEditedEvent(album, album));
             }
 
-            var qualifiedImports = decisions.Where(c => c.Approved)
-                .GroupBy(c => c.Item.Artist.Id, (i, s) => s
-                         .OrderByDescending(c => c.Item.Quality, new QualityModelComparer(s.First().Item.Artist.QualityProfile))
-                         .ThenByDescending(c => c.Item.Size))
-                .SelectMany(c => c)
+            var qualifiedImports = decisions
+                .Where(decision => decision.Approved)
+                .GroupBy(decision => decision.Item.Artist.Id)
+                .SelectMany(group => group
+                    .OrderByDescending(decision => decision.Item.Quality, new QualityModelComparer(group.First().Item.Artist.QualityProfile))
+                    .ThenByDescending(decision => decision.Item.Size))
                 .ToList();
 
             _logger.ProgressInfo($"Importing {qualifiedImports.Count} tracks");