diff --git a/Sources/AppBundle/config/parseOnWindowDetected.swift b/Sources/AppBundle/config/parseOnWindowDetected.swift
index 1d407908..679a9aff 100644
--- a/Sources/AppBundle/config/parseOnWindowDetected.swift
+++ b/Sources/AppBundle/config/parseOnWindowDetected.swift
@@ -77,7 +77,7 @@ private let matcherParsers: [String: any ParserProtocol<WindowDetectedCallbackMa
 ]
 
 private func upcast<T>(_ fun: @escaping @Sendable (Json, ConfigBacktrace) -> ParsedConfig<T>) -> @Sendable (Json, ConfigBacktrace) -> ParsedConfig<T?> {
-    { fun($0, $1).map { $0 } }
+    { fun($0, $1).map(Optional.init) }
 }
 
 func parseOnWindowDetectedArray(_ raw: Json, _ backtrace: ConfigBacktrace, _ errors: inout [ConfigParseError]) -> [WindowDetectedCallback] {
diff --git a/Sources/AppBundle/layout/refresh.swift b/Sources/AppBundle/layout/refresh.swift
index 78afc641..60038054 100644
--- a/Sources/AppBundle/layout/refresh.swift
+++ b/Sources/AppBundle/layout/refresh.swift
@@ -111,7 +111,7 @@ func refreshModel() {
 private func refresh() async throws {
     // Garbage collect terminated apps and windows before working with all windows
     let mapping = try await MacApp.refreshAllAndGetAliveWindowIds(frontmostAppBundleId: NSWorkspace.shared.frontmostApplication?.bundleIdentifier)
-    let aliveWindowIds = mapping.values.flatMap { $0 }.toSet()
+    let aliveWindowIds = mapping.values.flatMap(id).toSet()
 
     for window in MacWindow.allWindows {
         if !aliveWindowIds.contains(window.windowId) {
diff --git a/Sources/AppBundle/server.swift b/Sources/AppBundle/server.swift
index b5346f11..fa8e78bc 100644
--- a/Sources/AppBundle/server.swift
+++ b/Sources/AppBundle/server.swift
@@ -97,8 +97,8 @@ private func newConnection(_ connection: NWConnection) async { // todo add exit
             let _answer: Result<ServerAnswer, Error> = await Result {
                 try await runLightSession(.socketServer(command.args), token) { () throws in
                     let env = CmdEnv.init(
-                        windowId: request.windowId.flatMap { $0 },
-                        workspaceName: request.workspace.flatMap { $0 },
+                        windowId: request.windowId.flattenOptional(),
+                        workspaceName: request.workspace.flattenOptional(),
                     )
                     let cmdResult = try await command.run(env, CmdStdin(request.stdin))
                     return ServerAnswer(
diff --git a/Sources/Common/cmdArgs/ArgParser.swift b/Sources/Common/cmdArgs/ArgParser.swift
index a6f02dac..a67a5027 100644
--- a/Sources/Common/cmdArgs/ArgParser.swift
+++ b/Sources/Common/cmdArgs/ArgParser.swift
@@ -103,4 +103,4 @@ func parseCardinalOrDfsDirection(i: PosArgParserInput) -> ParsedCliArgs<Cardinal
     .init(parseEnum(i.arg, CardinalOrDfsDirection.self), advanceBy: 1)
 }
 
-func upcastArgParserFun<Input, T>(_ fun: @escaping ArgParserFun<Input, T>) -> ArgParserFun<Input, T?> { { fun($0).map { $0 } } }
+func upcastArgParserFun<Input, T>(_ fun: @escaping ArgParserFun<Input, T>) -> ArgParserFun<Input, T?> { { fun($0).map(Optional.init) } }
diff --git a/Sources/Common/cmdArgs/impl/ConfigCmdArgs.swift b/Sources/Common/cmdArgs/impl/ConfigCmdArgs.swift
index 1acc6d7f..45ce51c2 100644
--- a/Sources/Common/cmdArgs/impl/ConfigCmdArgs.swift
+++ b/Sources/Common/cmdArgs/impl/ConfigCmdArgs.swift
@@ -10,7 +10,7 @@ public struct ConfigCmdArgs: CmdArgs, Equatable {
             "--major-keys": trueBoolFlag(\.majorKeys),
             "--all-keys": trueBoolFlag(\.allKeys),
             "--config-path": trueBoolFlag(\.configPath),
-            "--get": singleValueSubArgParser(\.keyNameToGet, "<name>") { $0 },
+            "--get": singleValueSubArgParser(\.keyNameToGet, "<name>", id),
         ],
         posArgs: [],
     )
diff --git a/Sources/Common/cmdArgs/impl/ListWindowsCmdArgs.swift b/Sources/Common/cmdArgs/impl/ListWindowsCmdArgs.swift
index ca59b40f..eb1ef236 100644
--- a/Sources/Common/cmdArgs/impl/ListWindowsCmdArgs.swift
+++ b/Sources/Common/cmdArgs/impl/ListWindowsCmdArgs.swift
@@ -17,7 +17,7 @@ public struct ListWindowsCmdArgs: CmdArgs {
             "--monitor": ArgParser(\.filteringOptions.monitors, parseMonitorIds),
             "--workspace": ArgParser(\.filteringOptions.workspaces, parseWorkspaces),
             "--pid": singleValueSubArgParser(\.filteringOptions.pidFilter, "<pid>", Int32.init),
-            "--app-bundle-id": singleValueSubArgParser(\.filteringOptions.appIdFilter, "<app-bundle-id>") { $0 },
+            "--app-bundle-id": singleValueSubArgParser(\.filteringOptions.appIdFilter, "<app-bundle-id>", id),
 
             // Formatting flags
             "--format": formatParser(\._format, for: .window),
diff --git a/Sources/Common/cmdArgs/impl/TriggerBindingCmdArgs.swift b/Sources/Common/cmdArgs/impl/TriggerBindingCmdArgs.swift
index a2dc5a49..5991b29d 100644
--- a/Sources/Common/cmdArgs/impl/TriggerBindingCmdArgs.swift
+++ b/Sources/Common/cmdArgs/impl/TriggerBindingCmdArgs.swift
@@ -5,7 +5,7 @@ public struct TriggerBindingCmdArgs: CmdArgs {
         allowInConfig: true,
         help: trigger_binding_help_generated,
         flags: [
-            "--mode": singleValueSubArgParser(\._mode, "<mode-id>") { $0 },
+            "--mode": singleValueSubArgParser(\._mode, "<mode-id>", id),
         ],
         posArgs: [newMandatoryPosArgParser(\.binding, consumeStrCliArg, placeholder: "<binding>")],
     )
diff --git a/Sources/Common/cmdArgs/subcommandParsers.swift b/Sources/Common/cmdArgs/subcommandParsers.swift
index 3dc49d1c..126bb1db 100644
--- a/Sources/Common/cmdArgs/subcommandParsers.swift
+++ b/Sources/Common/cmdArgs/subcommandParsers.swift
@@ -6,9 +6,7 @@ protocol SubCommandParserProtocol<T>: Sendable {
 }
 
 extension SubCommandParserProtocol {
-    func parse(args: StrArrSlice) -> ParsedCmd<any CmdArgs> {
-        _parse(args).map { $0 }
-    }
+    func parse(args: StrArrSlice) -> ParsedCmd<any CmdArgs> { _parse(args).map(id) }
 }
 
 struct SubCommandParser<T: CmdArgs>: SubCommandParserProtocol, Sendable {
diff --git a/Sources/Common/model/clientServer.swift b/Sources/Common/model/clientServer.swift
index 63cabc50..20b75fb4 100644
--- a/Sources/Common/model/clientServer.swift
+++ b/Sources/Common/model/clientServer.swift
@@ -64,8 +64,8 @@ public struct ClientRequest: Codable, Sendable, ConvenienceCopyable, Equatable {
         var raw = ClientRequest(
             args: data.args,
             stdin: data.stdin,
-            windowId: data.windowId.flatMap { $0 },
-            workspace: data.workspace.flatMap { $0 },
+            windowId: data.windowId.flattenOptional(),
+            workspace: data.workspace.flattenOptional(),
         )
         let container = try decoder.container(keyedBy: CodingKeys.self)
         if !container.contains(.windowId) { raw.windowId = nil }
diff --git a/Sources/Common/util/OptionalEx.swift b/Sources/Common/util/OptionalEx.swift
index 7c28defc..ea4e6676 100644
--- a/Sources/Common/util/OptionalEx.swift
+++ b/Sources/Common/util/OptionalEx.swift
@@ -33,6 +33,13 @@ extension Optional {
         }
     }
 
+    public func flattenOptional<T>() -> T? where Wrapped == T? {
+        switch self {
+            case let x?: x
+            case nil: nil
+        }
+    }
+
     public var prettyDescription: String {
         if let unwrapped = self {
             return String(describing: unwrapped)
diff --git a/Sources/Common/util/SequenceEx.swift b/Sources/Common/util/SequenceEx.swift
index bdf917cb..6ba1a4cc 100644
--- a/Sources/Common/util/SequenceEx.swift
+++ b/Sources/Common/util/SequenceEx.swift
@@ -3,9 +3,7 @@ import AppKit
 import OrderedCollections
 
 extension Sequence {
-    public func filterNotNil<Unwrapped>() -> [Unwrapped] where Element == Unwrapped? {
-        compactMap { $0 }
-    }
+    public func filterNotNil<Unwrapped>() -> [Unwrapped] where Element == Unwrapped? { compactMap(id) }
 
     public func filterIsInstance<R>(of _: R.Type) -> [R] {
         var result: [R] = []
diff --git a/Sources/Common/util/commonUtil.swift b/Sources/Common/util/commonUtil.swift
index 31db62c9..795a3473 100644
--- a/Sources/Common/util/commonUtil.swift
+++ b/Sources/Common/util/commonUtil.swift
@@ -192,6 +192,9 @@ public func exitT<T>(_ exitCode: Int32, out: String? = nil, err: String? = nil)
     exit(exitCode)
 }
 
+/// 'id' stands for 'identity'. It's a common name in functional programming
+public func id<T>(_ t: T) -> T { t }
+
 @inlinable
 public func allowOnlyCancellationError<T>(_ block: () async throws -> sending T) async throws -> sending T {
     do {