Add SETNX command

Motivation:

The SETNX command is missing.

Modifications:

- Add SETNX command
- Add integration test

Result:

Users can set a key only if it does not already exist

Author: glbrntt

Sources/RediStack/Commands/StringCommands.swift

@@ -26,7 +26,7 @@ extension RedisClient {
         let args = [RESPValue(from: key)]
         return self.send(command: "GET", with: args)
     }
-    
+
     /// Get the value of a key, converting it to the desired type.
     ///
     /// [https://redis.io/commands/get](https://redis.io/commands/get)
@@ -55,7 +55,7 @@ extension RedisClient {
         return send(command: "MGET", with: args)
             .map()
     }
-    
+
     /// Gets the values of all specified keys, using `.null` to represent non-existant values.
     ///
     /// See [https://redis.io/commands/mget](https://redis.io/commands/mget)
@@ -68,7 +68,7 @@ extension RedisClient {
         return self.mget(keys)
             .map { return $0.map(Value.init(fromRESP:)) }
     }
-    
+
     /// Gets the values of all specified keys, using `.null` to represent non-existant values.
     ///
     /// See [https://redis.io/commands/mget](https://redis.io/commands/mget)
@@ -77,7 +77,7 @@ extension RedisClient {
     public func mget(_ keys: RedisKey...) -> EventLoopFuture<[RESPValue]> {
         return self.mget(keys)
     }
-    
+
     /// Gets the values of all specified keys, using `.null` to represent non-existant values.
     ///
     /// See [https://redis.io/commands/mget](https://redis.io/commands/mget)
@@ -111,7 +111,7 @@ extension RedisClient {
         return send(command: "APPEND", with: args)
             .map()
     }
-    
+
     /// Sets the value stored in the key provided, overwriting the previous value.
     ///
     /// Any previous expiration set on the key is discarded if the SET operation was successful.
@@ -133,6 +133,27 @@ extension RedisClient {
             .map { _ in () }
     }
 
+    /// Sets the key to the provided value if the key does not exist.
+    ///
+    /// [https://redis.io/commands/setnx](https://redis.io/commands/setnx)
+    /// - Important: Regardless of the type of data stored at the key, it will be overwritten to a "string" data type.
+    ///
+    /// ie. If the key is a reference to a Sorted Set, its value will be overwritten to be a "string" data type.
+    /// - Parameters:
+    ///     - key: The key to use to uniquely identify this value.
+    ///     - value: The value to set the key to.
+    /// - Returns: `true` if the operation successfully completed.
+    @inlinable
+    public func setnx<Value: RESPValueConvertible>(_ key: RedisKey, to value: Value) -> EventLoopFuture<Bool> {
+        let args: [RESPValue] = [
+            .init(from: key),
+            value.convertedToRESPValue()
+        ]
+        return self.send(command: "SETNX", with: args)
+            .map(to: Int.self)
+            .map { $0 == 1 }
+    }
+
     /// Sets each key to their respective new value, overwriting existing values.
     /// - Note: Use `msetnx(_:)` if you don't want to overwrite values.
     ///
@@ -157,7 +178,7 @@ extension RedisClient {
             .map(to: Int.self)
             .map { return $0 == 1 }
     }
-    
+
     @usableFromInline
     func _mset<Value: RESPValueConvertible>(
         command: String,

Tests/RediStackIntegrationTests/Commands/StringCommandsTests.swift

@@ -23,11 +23,11 @@ final class StringCommandsTests: RediStackIntegrationTestCase {
         try connection.set(#function, to: "value").wait()
         let r1: String? = try connection.get(#function, as: String.self).wait()
         XCTAssertEqual(r1, "value")
-        
+
         try connection.set(#function, to: 30).wait()
         let r2 = try connection.get(#function, as: Int.self).wait()
         XCTAssertEqual(r2, 30)
-        
+
         _ = try connection.delete(#function).wait()
         let r3: RESPValue = try connection.get(#function).wait()
         XCTAssertEqual(r3, .null)
@@ -51,7 +51,12 @@ final class StringCommandsTests: RediStackIntegrationTestCase {
         let val = try connection.get(#function, as: String.self).wait()
         XCTAssertEqual(val, "value")
     }
-    
+
+    func test_setnx() throws {
+        XCTAssertTrue(try connection.setnx(#function, to: "value").wait())
+        XCTAssertFalse(try connection.setnx(#function, to: "value").wait())
+    }
+
     func test_append() throws {
         let result = "value appended"
         XCTAssertNoThrow(try connection.append("value", to: #function).wait())
@@ -60,7 +65,7 @@ final class StringCommandsTests: RediStackIntegrationTestCase {
         let val = try connection.get(#function, as: String.self).wait()
         XCTAssertEqual(val, result)
     }
-    
+
     func test_mset() throws {
         let data: [RedisKey: Int] = [
             "first": 1,

Tests/RediStackIntegrationTests/XCTestManifests.swift

@@ -148,6 +148,7 @@ extension StringCommandsTests {
         ("test_mset", test_mset),
         ("test_msetnx", test_msetnx),
         ("test_set", test_set),
+        ("test_setnx", test_setnx),
     ]
 }