Fix/response ❤️ (#2383)

* Give all the responses some ❤️

As per #2299 be more consistent responses with returning empty collections vs null on responses.
Now that we dropped .NET 4.0 we can make the response IEnumerable and Dictionaries IReadOnly*

Made sure all the interfaces only define getters and not setters

* another pass at all response objects

* Make sure EmptyReadOnly returns actual ReadOnly* instances for the interfaces and not rely on implicit conversion.
Fix sorts on covariant hits having trouble going from JArray to ReadOnlyCollection<object>

* fix shard store response because Stores now needs an explicit JsonProperty

Author: Mpdreamz

src/Nest/Aggregations/Aggregate.cs

@@ -11,6 +11,7 @@ namespace Nest
 	[ExactContractJsonConverter(typeof(AggregateJsonConverter))]
 	public interface IAggregate
 	{
-		IDictionary<string, object> Meta { get; set; }
+		//TODO this public set is problematic
+		IReadOnlyDictionary<string, object> Meta { get; set; }
 	}
 }

src/Nest/Aggregations/AggregateJsonConverter.cs

@@ -61,7 +61,7 @@ private IAggregate ReadAggregate(JsonReader reader, JsonSerializer serializer)
 				case "buckets":
 				case "doc_count_error_upper_bound":
 					aggregate = GetMultiBucketAggregate(reader, serializer);
-					break;;
+					break;
 				case "count":
 					aggregate = GetStatsAggregate(reader, serializer);
 					break;
@@ -342,7 +342,7 @@ private IAggregate GetExtendedStatsAggregate(StatsAggregate statsMetric, JsonRea
 			return extendedStatsMetric;
 		}
 
-		private IDictionary<string, IAggregate> GetSubAggregates(JsonReader reader, JsonSerializer serializer)
+		private IReadOnlyDictionary<string, IAggregate> GetSubAggregates(JsonReader reader, JsonSerializer serializer)
 		{
 			if (reader.TokenType != JsonToken.PropertyName)
 				return null;
@@ -405,7 +405,7 @@ private IAggregate GetMultiBucketAggregate(JsonReader reader, JsonSerializer ser
 			if (reader.TokenType == JsonToken.EndArray)
 			{
 				reader.Read();
-				bucket.Items = Enumerable.Empty<IBucket>();
+				bucket.Items = EmptyReadOnly<IBucket>.Collection;
 				return bucket;
 			}
 			do
@@ -553,7 +553,7 @@ private IBucket GetKeyedBucket(JsonReader reader, JsonSerializer serializer)
 			if (property == "from" || property == "to")
 				return GetRangeBucket(reader, serializer, key);
 
-			var keyItem = new KeyedBucket {Key = key};
+			var keyItem = new KeyedBucket { Key = key };
 
 			if (property == "key_as_string")
 			{

src/Nest/Aggregations/AggregationsHelper.cs

@@ -6,13 +6,19 @@ namespace Nest
 {
 	public class AggregationsHelper
 	{
-		public IDictionary<string, IAggregate> Aggregations { get; protected internal set; }
+		public IReadOnlyDictionary<string, IAggregate> Aggregations { get; protected internal set; } = EmptyReadOnly<string, IAggregate>.Dictionary;
 
 		public AggregationsHelper() { }
 
-		public AggregationsHelper(IDictionary<string, IAggregate> aggregations)
+		protected AggregationsHelper(IDictionary<string, IAggregate> aggregations)
+		{
+			this.Aggregations = aggregations != null ?
+				new Dictionary<string, IAggregate>(aggregations)
+				: EmptyReadOnly<string, IAggregate>.Dictionary;
+		}
+		public AggregationsHelper(IReadOnlyDictionary<string, IAggregate> aggregations)
 		{
-			this.Aggregations = aggregations;
+			this.Aggregations = aggregations ?? EmptyReadOnly<string, IAggregate>.Dictionary;
 		}
 
 		public ValueAggregate Min(string key) => this.TryGet<ValueAggregate>(key);
@@ -164,11 +170,11 @@ public MultiBucketAggregate<HistogramBucket> Histogram(string key)
 		public MatrixStatsAggregate MatrixStats(string key) => this.TryGet<MatrixStatsAggregate>(key);
 
 
-		private TAggregation TryGet<TAggregation>(string key)
-			where TAggregation : class, IAggregate
+		private TAggregate TryGet<TAggregate>(string key)
+			where TAggregate : class, IAggregate
 		{
 			IAggregate agg;
-			return this.Aggregations.TryGetValue(key, out agg) ? agg as TAggregation : null;
+			return this.Aggregations.TryGetValue(key, out agg) ? agg as TAggregate : null;
 		}
 
 		private MultiBucketAggregate<TBucket> GetBucket<TBucket>(string key)

src/Nest/Aggregations/Bucket/BucketAggregate.cs

@@ -8,7 +8,7 @@ public abstract class BucketAggregateBase : AggregationsHelper, IAggregate
 		protected BucketAggregateBase() { }
 		protected BucketAggregateBase(IDictionary<string, IAggregate> aggregations) : base(aggregations) { }
 
-		public IDictionary<string, object> Meta { get; set; }
+		public IReadOnlyDictionary<string, object> Meta { get; set; } = EmptyReadOnly<string, object>.Dictionary;
 	}
 
 	public class MultiBucketAggregate<TBucket> : BucketAggregateBase
@@ -17,7 +17,7 @@ public class MultiBucketAggregate<TBucket> : BucketAggregateBase
 		public MultiBucketAggregate() { }
 		public MultiBucketAggregate(IDictionary<string, IAggregate> aggregations) : base(aggregations) { }
 
-		public IList<TBucket> Buckets { get; set; }
+		public IReadOnlyCollection<TBucket> Buckets { get; set; } = EmptyReadOnly<TBucket>.Collection;
 	}
 
 	public class SingleBucketAggregate : BucketAggregateBase
@@ -31,10 +31,10 @@ public SingleBucketAggregate(IDictionary<string, IAggregate> aggregations) : bas
 	// Intermediate object used for deserialization
 	public class BucketAggregate : IAggregate
 	{
-		public IEnumerable<IBucket> Items { get; set; }
+		public IReadOnlyCollection<IBucket> Items { get; set; } = EmptyReadOnly<IBucket>.Collection;
 		public long? DocCountErrorUpperBound { get; set; }
 		public long? SumOtherDocCount { get; set; }
-		public IDictionary<string, object> Meta { get; set; }
+		public IReadOnlyDictionary<string, object> Meta { get; set; } = EmptyReadOnly<string, object>.Dictionary;
 		public long DocCount { get; set; }
 	}
 }

src/Nest/Aggregations/Matrix/MatrixAggregate.cs

@@ -8,6 +8,6 @@ namespace Nest
 {
 	public abstract class MatrixAggregateBase : IAggregate
 	{
-		public IDictionary<string, object> Meta { get; set; }
+		public IReadOnlyDictionary<string, object> Meta { get; set; } = EmptyReadOnly<string, object>.Dictionary;
 	}
 }

src/Nest/Aggregations/Metric/MetricAggregate.cs

@@ -5,6 +5,6 @@ namespace Nest
 {
 	public abstract class MetricAggregateBase : IAggregate
 	{
-		public IDictionary<string, object> Meta { get; set; }
+		public IReadOnlyDictionary<string, object> Meta { get;  set; } = EmptyReadOnly<string, object>.Dictionary;
 	}
 }

src/Nest/Aggregations/Metric/TopHits/TopHitsAggregate.cs

@@ -16,29 +16,33 @@ public class TopHitsAggregate : MetricAggregateBase
 		public double? MaxScore { get; set; }
 
 		public TopHitsAggregate() { }
-		
+
 		internal TopHitsAggregate(IEnumerable<JObject> hits)
 		{
-			_hits = hits;
+			_hits = hits ?? Enumerable.Empty<JObject>();
 		}
 
 		internal TopHitsAggregate(IEnumerable<JObject> hits, JsonSerializer serializer)
 		{
-			_hits = hits;
+			_hits = hits ?? Enumerable.Empty<JObject>();;
 			_defaultSerializer = serializer;
 		}
 
-		public IEnumerable<Hit<T>> Hits<T>(JsonSerializer serializer = null) 
+		private IEnumerable<Hit<T>> ConvertHits<T>(JsonSerializer serializer = null)
 			where T : class
 		{
 			var s = serializer ?? _defaultSerializer;
 
-			return s != null 
-				? _hits.Select(h => h.ToObject<Hit<T>>(s)) 
+			return s != null
+				? _hits.Select(h => h.ToObject<Hit<T>>(s))
 				: _hits.Select(h => h.ToObject<Hit<T>>());
 		}
 
-		public IEnumerable<T> Documents<T>(JsonSerializer serializer = null) where T : class =>
-			this.Hits<T>(serializer).Select(h => h.Source);
+		public IReadOnlyCollection<Hit<T>> Hits<T>(JsonSerializer serializer = null)
+			where T : class =>
+			this.ConvertHits<T>(serializer).ToList().AsReadOnly();
+
+		public IReadOnlyCollection<T> Documents<T>(JsonSerializer serializer = null) where T : class =>
+			this.ConvertHits<T>(serializer).Select(h => h.Source).ToList().AsReadOnly();
 	}
 }

src/Nest/Cat/CatResponse.cs

@@ -1,18 +1,19 @@
 using System.Collections.Generic;
+using System.Linq;
 using Newtonsoft.Json;
 
 namespace Nest
 {
 	public interface ICatResponse<out TCatRecord> : IResponse
 		where TCatRecord : ICatRecord
 	{
-		IEnumerable<TCatRecord> Records { get; }
+		IReadOnlyCollection<TCatRecord> Records { get; }
 	}
 
 	[JsonObject]
 	public class CatResponse<TCatRecord> : ResponseBase, ICatResponse<TCatRecord>
 		where TCatRecord : ICatRecord
 	{
-		public IEnumerable<TCatRecord> Records { get; internal set; }
+		public IReadOnlyCollection<TCatRecord> Records { get; internal set; } = EmptyReadOnly<TCatRecord>.Collection;
 	}
 }

src/Nest/Cat/ElasticClient-Cat.cs

@@ -13,7 +13,7 @@ public partial class ElasticClient
 		private CatResponse<TCatRecord> DeserializeCatResponse<TCatRecord>(IApiCallDetails response, Stream stream)
 			where TCatRecord : ICatRecord
 		{
-			var records = this.Serializer.Deserialize<IEnumerable<TCatRecord>>(stream);
+			var records = this.Serializer.Deserialize<IReadOnlyCollection<TCatRecord>>(stream);
 			return new CatResponse<TCatRecord> { Records = records };
 		}
 

src/Nest/Cluster/ClusterAllocationExplain/ClusterAllocationExplainResponse.cs

@@ -9,58 +9,58 @@ namespace Nest
 	public interface IClusterAllocationExplainResponse : IResponse
 	{
 		[JsonProperty("shard")]
-		ShardAllocationExplanation Shard { get; set; }
+		ShardAllocationExplanation Shard { get; }
 
 		[JsonProperty("assigned")]
-		bool Assigned { get; set; }
+		bool Assigned { get; }
 
 		[JsonProperty("assigned_node_id")]
-		string AssignedNodeId { get; set; }
+		string AssignedNodeId { get; }
 
 		[JsonProperty("shard_state_fetch_pending")]
-		bool ShardStateFetchPending { get; set; }
+		bool ShardStateFetchPending { get; }
 
 		[JsonProperty("unassigned_info")]
-		UnassignedInformation UnassignedInformation { get; set; }
+		UnassignedInformation UnassignedInformation { get; }
 
 		[JsonProperty("allocation_delay")]
-		string AllocationDelay { get; set; }
+		string AllocationDelay { get; }
 
 		[JsonProperty("allocation_delay_ms")]
-		long AllocationDelayInMilliseconds { get; set; }
+		long AllocationDelayInMilliseconds { get; }
 
 		[JsonProperty("remaining_delay")]
-		string RemainingDelay { get; set; }
+		string RemainingDelay { get; }
 
 		[JsonProperty("remaining_delay_ms")]
-		long RemainingDelayInMilliseconds { get; set; }
+		long RemainingDelayInMilliseconds { get; }
 
 		[JsonProperty("nodes")]
 		[JsonConverter(typeof(VerbatimDictionaryKeysJsonConverter))]
-		Dictionary<string, NodeAllocationExplanation> Nodes { get; set; }
+		IReadOnlyDictionary<string, NodeAllocationExplanation> Nodes { get; }
 	}
 
 	public class ClusterAllocationExplainResponse : ResponseBase, IClusterAllocationExplainResponse
 	{
-		public ShardAllocationExplanation Shard { get; set; }
+		public ShardAllocationExplanation Shard { get; internal set; }
 
-		public bool Assigned { get; set; }
+		public bool Assigned { get; internal set; }
 
-		public string AssignedNodeId { get; set; }
+		public string AssignedNodeId { get; internal set; }
 
-		public bool ShardStateFetchPending { get; set; }
+		public bool ShardStateFetchPending { get; internal set; }
 
-		public UnassignedInformation UnassignedInformation { get; set; }
+		public UnassignedInformation UnassignedInformation { get; internal set; }
 
-		public string AllocationDelay { get; set; }
+		public string AllocationDelay { get; internal set; }
 
-		public long AllocationDelayInMilliseconds { get; set; }
+		public long AllocationDelayInMilliseconds { get; internal set; }
 
-		public string RemainingDelay { get; set; }
+		public string RemainingDelay { get; internal set; }
 
-		public long RemainingDelayInMilliseconds { get; set; }
+		public long RemainingDelayInMilliseconds { get; internal set; }
 
-		public Dictionary<string, NodeAllocationExplanation> Nodes { get; set; }
+		public IReadOnlyDictionary<string, NodeAllocationExplanation> Nodes { get; internal set; } = EmptyReadOnly<string, NodeAllocationExplanation>.Dictionary;
 	}
 
 	[JsonConverter(typeof(StringEnumConverter))]
@@ -86,7 +86,7 @@ public class NodeAllocationExplanation
 		public string NodeName { get; set; }
 
 		[JsonProperty("node_attributes")]
-		public Dictionary<string,string> NodeAttributes { get; set; }
+		public IReadOnlyDictionary<string, string> NodeAttributes { get; set; } = EmptyReadOnly<string, string>.Dictionary;
 
 		[JsonProperty("store")]
 		public AllocationStore Store { get; set; }
@@ -102,7 +102,7 @@ public class NodeAllocationExplanation
 		public float Weight { get; set; }
 
 		[JsonProperty("decisions")]
-		public IEnumerable<AllocationDecision> Decisions { get; set; }
+		public IReadOnlyCollection<AllocationDecision> Decisions { get; set; } = EmptyReadOnly<AllocationDecision>.Collection;
 	}
 
 	[JsonObject]
@@ -160,68 +160,68 @@ public enum UnassignedInformationReason
 		IndexCreated,
 
 		///<summary>
-        /// Unassigned as a result of a full cluster recovery.
-        ///</summary>
+		/// Unassigned as a result of a full cluster recovery.
+		///</summary>
 		[EnumMember(Value = "CLUSTER_RECOVERED")]
 		ClusterRecovered,
 
 		///<summary>
-        /// Unassigned as a result of opening a closed index.
-        ///</summary>
+		/// Unassigned as a result of opening a closed index.
+		///</summary>
 		[EnumMember(Value = "INDEX_REOPENED")]
 		IndexReopened,
 
 		///<summary>
-        /// Unassigned as a result of importing a dangling index.
-        ///</summary>
+		/// Unassigned as a result of importing a dangling index.
+		///</summary>
 		[EnumMember(Value = "DANGLING_INDEX_IMPORTED")]
 		DanglingIndexImported,
 
 		///<summary>
-        /// Unassigned as a result of restoring into a new index.
-        ///</summary>
+		/// Unassigned as a result of restoring into a new index.
+		///</summary>
 		[EnumMember(Value = "NEW_INDEX_RESTORED")]
 		NewIndexRestored,
 
 		///<summary>
-        /// Unassigned as a result of restoring into a closed index.
-        ///</summary>
+		/// Unassigned as a result of restoring into a closed index.
+		///</summary>
 		[EnumMember(Value = "EXISTING_INDEX_RESTORED")]
 		ExistingIndexRestored,
 
 		///<summary>
-        /// Unassigned as a result of explicit addition of a replica.
-        ///</summary>
+		/// Unassigned as a result of explicit addition of a replica.
+		///</summary>
 		[EnumMember(Value = "REPLICA_ADDED")]
 		ReplicaAdded,
 
 		///<summary>
-        /// Unassigned as a result of a failed allocation of the shard.
-        ///</summary>
+		/// Unassigned as a result of a failed allocation of the shard.
+		///</summary>
 		[EnumMember(Value = "ALLOCATION_FAILED")]
 		AllocationFailed,
 
 		///<summary>
-        /// Unassigned as a result of the node hosting it leaving the cluster.
-        ///</summary>
+		/// Unassigned as a result of the node hosting it leaving the cluster.
+		///</summary>
 		[EnumMember(Value = "NODE_LEFT")]
 		NodeLeft,
 
 		///<summary>
-        /// Unassigned as a result of explicit cancel reroute command.
-        ///</summary>
+		/// Unassigned as a result of explicit cancel reroute command.
+		///</summary>
 		[EnumMember(Value = "REROUTE_CANCELLED")]
 		RerouteCancelled,
 
 		///<summary>
-        /// When a shard moves from started back to initializing, for example, during shadow replica
-        ///</summary>
+		/// When a shard moves from started back to initializing, for example, during shadow replica
+		///</summary>
 		[EnumMember(Value = "REINITIALIZED")]
 		Reinitialized,
 
 		///<summary>
-        /// A better replica location is identified and causes the existing replica allocation to be cancelled.
-        ///</summary>
+		/// A better replica location is identified and causes the existing replica allocation to be cancelled.
+		///</summary>
 		[EnumMember(Value = "REALLOCATED_REPLICA")]
 		ReallocatedReplica
 	}