Make Error types Hashable + Equatable (#69)

* Make Error types Hashable + Equatable

Modifications:

* `KafkaError`: make `Equatable`
* `KafkaAcknowledgedMessageError`: make `Equatable` + `Hashable`

* Review Franz

Modifications:

* remove duplicate `Equatable` conformances, `Hashable` implies
  `Equatable`
* only take the backing `code` into account for `Hashable` and
  `Equatable` conformance of the `Kafka*Error` types

* * remove redundant `Equatable` annotations

Author: felixschlegel

Sources/SwiftKafka/Configuration/KafkaConsumerConfiguration.swift

@@ -15,7 +15,7 @@
 import Crdkafka
 import struct Foundation.UUID
 
-public struct KafkaConsumerConfiguration: Hashable, Equatable {
+public struct KafkaConsumerConfiguration: Hashable {
     // MARK: - SwiftKafka-specific Config properties
 
     /// The backpressure strategy to be used for message consumption.
@@ -474,8 +474,8 @@ public struct KafkaConsumerConfiguration: Hashable, Equatable {
 
 extension KafkaSharedConfiguration {
     /// A struct representing different back pressure strategies for consuming messages in ``KafkaConsumer``.
-    public struct BackPressureStrategy: Hashable, Equatable {
-        enum _BackPressureStrategy: Hashable, Equatable {
+    public struct BackPressureStrategy: Hashable {
+        enum _BackPressureStrategy: Hashable {
             case watermark(low: Int, high: Int)
         }
 
@@ -498,8 +498,8 @@ extension KafkaSharedConfiguration {
     }
 
     /// A struct representing the different Kafka message consumption strategies.
-    public struct ConsumptionStrategy: Hashable, Equatable {
-        enum _ConsumptionStrategy: Hashable, Equatable {
+    public struct ConsumptionStrategy: Hashable {
+        enum _ConsumptionStrategy: Hashable {
             case partition(topic: String, partition: KafkaPartition, offset: Int)
             case group(groupID: String, topics: [String])
         }
@@ -535,7 +535,7 @@ extension KafkaSharedConfiguration {
     }
 
     /// Available actions to take when there is no initial offset in offset store / offset is out of range.
-    public struct AutoOffsetReset: Hashable, Equatable, CustomStringConvertible {
+    public struct AutoOffsetReset: Hashable, CustomStringConvertible {
         public let description: String
 
         /// Automatically reset the offset to the smallest offset.

Sources/SwiftKafka/Configuration/KafkaProducerConfiguration.swift

@@ -12,7 +12,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-public struct KafkaProducerConfiguration: Hashable, Equatable {
+public struct KafkaProducerConfiguration: Hashable {
     var dictionary: [String: String] = [:]
 
     // MARK: - Producer-specific Config Properties

Sources/SwiftKafka/Configuration/KafkaSharedConfiguration.swift

@@ -15,7 +15,7 @@
 /// Collection of `enum` types used in the configuration structs this library provides.
 public enum KafkaSharedConfiguration {
     /// Available debug contexts to enable.
-    public struct DebugOption: Hashable, Equatable, CustomStringConvertible {
+    public struct DebugOption: Hashable, CustomStringConvertible {
         public let description: String
 
         public static let generic = DebugOption(description: "generic")
@@ -38,7 +38,7 @@ public enum KafkaSharedConfiguration {
     }
 
     /// Available IP address families.
-    public struct IPAddressFamily: Hashable, Equatable, CustomStringConvertible {
+    public struct IPAddressFamily: Hashable, CustomStringConvertible {
         public let description: String
 
         /// Use any IP address family.
@@ -50,7 +50,7 @@ public enum KafkaSharedConfiguration {
     }
 
     /// Protocol used to communicate with brokers.
-    public struct SecurityProtocol: Hashable, Equatable, CustomStringConvertible {
+    public struct SecurityProtocol: Hashable, CustomStringConvertible {
         public let description: String
 
         /// Send messages as plaintext (no security protocol used).
@@ -64,7 +64,7 @@ public enum KafkaSharedConfiguration {
     }
 
     /// Available SASL mechanisms that can be used for authentication.
-    public struct SASLMechanism: Hashable, Equatable, CustomStringConvertible {
+    public struct SASLMechanism: Hashable, CustomStringConvertible {
         public let description: String
 
         /// Use the GSSAPI mechanism.

Sources/SwiftKafka/Configuration/KafkaTopicConfiguration.swift

@@ -13,7 +13,7 @@
 //===----------------------------------------------------------------------===//
 
 /// Used to configure new topics created by the ``KafkaProducer``.
-public struct KafkaTopicConfiguration: Hashable, Equatable {
+public struct KafkaTopicConfiguration: Hashable {
     var dictionary: [String: String] = [:]
 
     /// This field indicates the number of acknowledgements the leader broker must receive from ISR brokers before responding to the request: 0=Broker does not send any response/ack to client, -1 or all=Broker will block until message is committed by all in sync replicas (ISRs). If there are less than min.insync.replicas (broker configuration) in the ISR set the produce request will fail.
@@ -89,7 +89,7 @@ public struct KafkaTopicConfiguration: Hashable, Equatable {
 
 extension KafkaSharedConfiguration {
     /// Partitioner. Computes the partition that a message is stored in.
-    public struct Partitioner: Hashable, Equatable, CustomStringConvertible {
+    public struct Partitioner: Hashable, CustomStringConvertible {
         public let description: String
 
         /// Random distribution.
@@ -109,7 +109,7 @@ extension KafkaSharedConfiguration {
     }
 
     /// Process to compress and decompress data.
-    public struct CompressionCodec: Hashable, Equatable, CustomStringConvertible {
+    public struct CompressionCodec: Hashable, CustomStringConvertible {
         public let description: String
 
         /// No compression.

Sources/SwiftKafka/KafkaAcknowledgedMessageError.swift

@@ -15,6 +15,9 @@
 import Crdkafka
 
 /// Error caused by the Kafka cluster when trying to process a message produced by ``KafkaProducer``.
+///
+/// - Note: `Hashable` conformance only considers the underlying ``KafkaAcknowledgedMessageError/error``'s
+/// ``KafkaError/code``.
 public struct KafkaAcknowledgedMessageError: Error, CustomStringConvertible {
     /// Identifier of the message that caused the error.
     public var messageID: UInt
@@ -62,3 +65,15 @@ public struct KafkaAcknowledgedMessageError: Error, CustomStringConvertible {
         )
     }
 }
+
+// MARK: - KafkaAcknowledgedMessageError + Hashable
+
+extension KafkaAcknowledgedMessageError: Hashable {
+    public static func == (lhs: KafkaAcknowledgedMessageError, rhs: KafkaAcknowledgedMessageError) -> Bool {
+        return lhs.error == rhs.error
+    }
+
+    public func hash(into hasher: inout Hasher) {
+        hasher.combine(self.error)
+    }
+}

Sources/SwiftKafka/KafkaError.swift

@@ -14,7 +14,10 @@
 
 import Crdkafka
 
-public struct KafkaError: Error, Hashable, CustomStringConvertible {
+/// An error that can occur on `Kafka` operations
+///
+/// - Note: `Hashable` conformance only considers the ``KafkaError/code``.
+public struct KafkaError: Error, CustomStringConvertible {
     private var backing: Backing
 
     /// Represents the kind of error that was encountered.
@@ -192,6 +195,8 @@ extension KafkaError {
     }
 }
 
+// MARK: - KafkaError + Backing
+
 extension KafkaError {
     final class Backing: Hashable {
         var code: KafkaError.ErrorCode
@@ -228,3 +233,15 @@ extension KafkaError {
         }
     }
 }
+
+// MARK: - KafkaError + Hashable
+
+extension KafkaError: Hashable {
+    public static func == (lhs: KafkaError, rhs: KafkaError) -> Bool {
+        return lhs.backing == rhs.backing
+    }
+
+    public func hash(into hasher: inout Hasher) {
+        hasher.combine(self.backing)
+    }
+}