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Add Blocking List Pop Commands
Motivation: To be a comprehensive library, all commands should be implemented, even if they are highly discouraged. List's collection of commands were missing `brpop`, `blpop`, and `brpoplpush`. Modifications: `brpop`, `blpop` and `brpoplpush` are supported with defaults and overloads for an easier API. Result: Users now have access to `brpop`, `blpop` and `brpoplpush` commands.
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‎Sources/NIORedis/Commands/ListCommands.swift

Lines changed: 140 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -117,6 +117,33 @@ extension RedisClient {
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public func rpoplpush(from source: String, to dest: String) -> EventLoopFuture<RESPValue> {
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return send(command: "RPOPLPUSH", with: [source, dest])
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}
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/// Pops the last element from a source list and pushes it to a destination list, blocking until
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/// an element is available from the source list.
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///
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/// - Important:
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/// This will block the connection from completing further commands until an element
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/// is available to pop from the source list.
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///
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/// It is **highly** recommended to set a reasonable `timeout`
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/// or to use the non-blocking `rpoplpush` method where possible.
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///
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/// See [https://redis.io/commands/brpoplpush](https://redis.io/commands/brpoplpush)
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/// - Parameters:
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/// - source: The key of the list to pop from.
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/// - dest: The key of the list to push to.
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/// - timeout: The time (in seconds) to wait. `0` means indefinitely.
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/// - Returns: The element popped from the source list and pushed to the destination,
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/// or `nil` if the timeout was reached.
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@inlinable
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public func brpoplpush(
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from source: String,
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to dest: String,
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timeout: Int = 0
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) -> EventLoopFuture<RESPValue?> {
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return send(command: "BRPOPLPUSH", with: [source, dest, timeout])
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.map { $0.isNull ? nil: $0 }
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}
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}
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// MARK: Insert
@@ -250,3 +277,116 @@ extension RedisClient {
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.mapFromRESP()
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}
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}
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// MARK: Blocking Pop
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extension RedisClient {
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/// Removes the first element of a list, blocking until an element is available.
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///
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/// - Important:
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/// This will block the connection from completing further commands until an element
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/// is available to pop from the list.
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///
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/// It is **highly** recommended to set a reasonable `timeout`
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/// or to use the non-blocking `lpop` method where possible.
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///
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/// See [https://redis.io/commands/blpop](https://redis.io/commands/blpop)
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/// - Parameters:
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/// - key: The key of the list to pop from.
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/// - Returns: The element that was popped from the list, or `nil` if the timout was reached.
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@inlinable
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public func blpop(from key: String, timeout: Int = 0) -> EventLoopFuture<RESPValue?> {
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return blpop(from: [key], timeout: timeout)
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.map { $0?.1 }
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}
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/// Removes the first element of a list, blocking until an element is available.
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///
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/// - Important:
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/// This will block the connection from completing further commands until an element
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/// is available to pop from the group of lists.
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///
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/// It is **highly** recommended to set a reasonable `timeout`
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/// or to use the non-blocking `lpop` method where possible.
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///
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/// See [https://redis.io/commands/blpop](https://redis.io/commands/blpop)
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/// - Parameters:
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/// - keys: The keys of lists in Redis that should be popped from.
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/// - timeout: The time (in seconds) to wait. `0` means indefinitely.
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/// - Returns:
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/// If timeout was reached, `nil`.
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///
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/// Otherwise, the key of the list the element was removed from and the popped element.
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@inlinable
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public func blpop(
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from keys: [String],
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timeout: Int = 0
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) -> EventLoopFuture<(String, RESPValue)?> {
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return _bpop(command: "BLPOP", keys, timeout)
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}
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/// Removes the last element of a list, blocking until an element is available.
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///
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/// - Important:
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/// This will block the connection from completing further commands until an element
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/// is available to pop from the list.
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///
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/// It is **highly** recommended to set a reasonable `timeout`
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/// or to use the non-blocking `rpop` method where possible.
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///
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/// See [https://redis.io/commands/brpop](https://redis.io/commands/brpop)
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/// - Parameters:
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/// - key: The key of the list to pop from.
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/// - Returns: The element that was popped from the list, or `nil` if the timout was reached.
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@inlinable
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public func brpop(from key: String, timeout: Int = 0) -> EventLoopFuture<RESPValue?> {
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return brpop(from: [key], timeout: timeout)
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.map { $0?.1 }
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}
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/// Removes the last element of a list, blocking until an element is available.
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///
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/// - Important:
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/// This will block the connection from completing further commands until an element
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/// is available to pop from the group of lists.
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///
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/// It is **highly** recommended to set a reasonable `timeout`
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/// or to use the non-blocking `rpop` method where possible.
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///
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/// See [https://redis.io/commands/brpop](https://redis.io/commands/brpop)
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/// - Parameters:
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/// - keys: The keys of lists in Redis that should be popped from.
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/// - timeout: The time (in seconds) to wait. `0` means indefinitely.
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/// - Returns:
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/// If timeout was reached, `nil`.
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///
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/// Otherwise, the key of the list the element was removed from and the popped element.
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@inlinable
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public func brpop(
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from keys: [String],
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timeout: Int = 0
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) -> EventLoopFuture<(String, RESPValue)?> {
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return _bpop(command: "BRPOP", keys, timeout)
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}
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@usableFromInline
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func _bpop(
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command: String,
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_ keys: [String],
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_ timeout: Int
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) -> EventLoopFuture<(String, RESPValue)?> {
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let args = keys as [RESPValueConvertible] + [timeout]
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return send(command: command, with: args)
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.flatMapThrowing {
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guard !$0.isNull else { return nil }
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guard let response = [RESPValue]($0) else {
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throw NIORedisError.responseConversion(to: [RESPValue].self)
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}
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assert(response.count == 2, "Unexpected response size returned!")
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guard let key = response[0].string else {
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throw NIORedisError.assertionFailure(message: "Unexpected structure in response: \(response)")
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}
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return (key, response[1])
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}
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}
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}

‎Tests/NIORedisTests/Commands/ListCommandsTests.swift

Lines changed: 61 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -102,6 +102,22 @@ final class ListCommandsTests: XCTestCase {
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XCTAssertEqual(try connection.llen(of: "second").wait(), 1)
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}
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func test_brpoplpush() throws {
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_ = try connection.lpush([10], into: "first").wait()
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let element = try connection.brpoplpush(from: "first", to: "second").wait() ?? .null
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XCTAssertEqual(Int(element), 10)
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let blockingConnection = try Redis.makeConnection().wait()
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let expectation = XCTestExpectation(description: "brpoplpush should never return")
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_ = blockingConnection.bzpopmin(from: #function)
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.always { _ in expectation.fulfill() }
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let result = XCTWaiter.wait(for: [expectation], timeout: 1)
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XCTAssertEqual(result, .timedOut)
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try blockingConnection.channel.close().wait()
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}
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func test_linsert() throws {
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_ = try connection.lpush([10], into: #function).wait()
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@@ -129,6 +145,27 @@ final class ListCommandsTests: XCTestCase {
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XCTAssertEqual(Int(element), 30)
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}
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func test_blpop() throws {
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let nilPop = try connection.blpop(from: #function, timeout: 1).wait()
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XCTAssertNil(nilPop)
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_ = try connection.lpush([10, 20, 30], into: "first").wait()
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let pop1 = try connection.blpop(from: "first").wait() ?? .null
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XCTAssertEqual(Int(pop1), 30)
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let pop2 = try connection.blpop(from: ["fake", "first"]).wait()
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XCTAssertEqual(pop2?.0, "first")
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let blockingConnection = try Redis.makeConnection().wait()
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let expectation = XCTestExpectation(description: "blpop should never return")
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_ = blockingConnection.bzpopmin(from: #function)
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.always { _ in expectation.fulfill() }
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let result = XCTWaiter.wait(for: [expectation], timeout: 1)
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XCTAssertEqual(result, .timedOut)
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try blockingConnection.channel.close().wait()
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}
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func test_lpush() throws {
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_ = try connection.rpush([10, 20, 30], into: #function).wait()
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@@ -165,6 +202,27 @@ final class ListCommandsTests: XCTestCase {
165202
XCTAssertTrue(result.isNull)
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}
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func test_brpop() throws {
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let nilPop = try connection.brpop(from: #function, timeout: 1).wait()
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XCTAssertNil(nilPop)
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_ = try connection.lpush([10, 20, 30], into: "first").wait()
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let pop1 = try connection.brpop(from: "first").wait() ?? .null
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XCTAssertEqual(Int(pop1), 10)
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let pop2 = try connection.brpop(from: ["fake", "first"]).wait()
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XCTAssertEqual(pop2?.0, "first")
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let blockingConnection = try Redis.makeConnection().wait()
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let expectation = XCTestExpectation(description: "brpop should never return")
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_ = blockingConnection.bzpopmin(from: #function)
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.always { _ in expectation.fulfill() }
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let result = XCTWaiter.wait(for: [expectation], timeout: 1)
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XCTAssertEqual(result, .timedOut)
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try blockingConnection.channel.close().wait()
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}
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func test_rpush() throws {
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_ = try connection.lpush([10, 20, 30], into: #function).wait()
170228

@@ -195,11 +253,14 @@ final class ListCommandsTests: XCTestCase {
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("test_lrem", test_lrem),
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("test_lrange", test_lrange),
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("test_rpoplpush", test_rpoplpush),
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("test_brpoplpush", test_brpoplpush),
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("test_linsert", test_linsert),
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("test_lpop", test_lpop),
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("test_blpop", test_blpop),
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("test_lpush", test_lpush),
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("test_lpushx", test_lpushx),
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("test_rpop", test_rpop),
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("test_brpop", test_brpop),
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("test_rpush", test_rpush),
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("test_rpushx", test_rpushx),
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]

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