Fix installer output parsing deadlock

.swiftlint.yml

@@ -51,7 +51,7 @@ file_length:
   ignore_comment_only_lines: true
   warning: 500
 file_name:
-  excluded: [Group.swift, User.swift]
+  excluded: [Group.swift, Process.swift, User.swift]
 file_types_order:
   order:
   - main_type

Sources/mas/AppStore/AppStoreAction+download.swift

@@ -234,7 +234,7 @@ private actor DownloadQueueObserver: CKDownloadQueueObserver {
 		prevPhaseType = snapshot.activePhaseType
 	}
 
-	private func removed(_ snapshot: DownloadSnapshot) {
+	private func removed(_ snapshot: DownloadSnapshot) async {
 		MAS.printer.clearCurrentLine(of: .standardOutput)
 
 		do {
@@ -250,7 +250,7 @@ private actor DownloadQueueObserver: CKDownloadQueueObserver {
 					"progress cannot be displayed",
 					terminator: "",
 				)
-				try install(appNameAndVersion: snapshot.appNameAndVersion)
+				try await install(appNameAndVersion: snapshot.appNameAndVersion)
 				MAS.printer.clearCurrentLine(of: .standardOutput)
 			} else {
 				guard !snapshot.isFailed else {
@@ -289,15 +289,39 @@ private actor DownloadQueueObserver: CKDownloadQueueObserver {
 		return hardLinkURL
 	}
 
-	private func install(appNameAndVersion: String) throws {
+	private func install(appNameAndVersion: String) async throws {
 		guard let pkgHardLinkPath = pkgHardLinkURL?.path(percentEncoded: false) else {
 			throw MASError.error("Failed to find pkg to \(action) \(appNameAndVersion)")
 		}
 		guard let receiptHardLinkURL else {
 			throw MASError.error("Failed to find receipt to import for \(appNameAndVersion)")
 		}
 
-		let appFolderURL = try installPkg(appNameAndVersion: appNameAndVersion)
+		let (_, standardErrorString) = try await run(
+			"/usr/sbin/installer",
+			"-dumplog",
+			"-pkg",
+			pkgHardLinkPath,
+			"-target",
+			"/",
+			errorMessage: "Failed to \(action) \(appNameAndVersion) from \(pkgHardLinkPath)",
+		) { process in try run(asEffectiveUID: 0, andEffectiveGID: 0) { try process.run() } }
+
+		let appFolderURLMatches = standardErrorString.matches(of: unsafe appFolderURLRegex)
+		// swiftlint:disable:next prefer_key_path
+		guard let appFolderURLSubstring = appFolderURLMatches.compactMap({ $0.1 }).min(by: { $0.count < $1.count }) else {
+			throw MASError.error( // swiftformat:disable:previous preferKeyPath
+				"Failed to find app folder URL in installer output for \(appNameAndVersion)",
+				error: standardErrorString,
+			)
+		}
+		guard let appFolderURL = URL(string: String(appFolderURLSubstring)) else {
+			throw MASError.error(
+				"Failed to parse app folder URL for \(appNameAndVersion) from \(appFolderURLSubstring)",
+				error: standardErrorString,
+			)
+		}
+
 		let receiptURL = appFolderURL.appending(path: "Contents/_MASReceipt/receipt", directoryHint: .notDirectory)
 		do {
 			let fileManager = FileManager.default
@@ -323,96 +347,14 @@ private actor DownloadQueueObserver: CKDownloadQueueObserver {
 			)
 		}
 
-		let process = Process()
-		process.executableURL = URL(filePath: "/usr/bin/mdimport", directoryHint: .notDirectory)
-		process.arguments = [appFolderURL.path(percentEncoded: false)]
-		let standardOutputPipe = Pipe()
-		process.standardOutput = standardOutputPipe
-		let standardErrorPipe = Pipe()
-		process.standardError = standardErrorPipe
-		do {
-			try process.run()
-		} catch {
-			throw MASError.error("Failed to \(action) \(appNameAndVersion) from \(pkgHardLinkPath)", error: error)
-		}
-		process.waitUntilExit()
-		guard process.terminationStatus == 0 else {
-			throw MASError.error(
-				"""
-				Failed to \(action) \(appNameAndVersion) from \(pkgHardLinkPath)
-				Exit status: \(process.terminationStatus)\(
-					try standardOutputPipe.fileHandleForReading
-					.readToEnd() // swiftformat:disable indent
-					.flatMap { String(data: $0, encoding: .utf8) }?
-					.trimmingCharacters(in: .whitespacesAndNewlines)
-					.prependIfNotEmpty("\n\nStandard output:\n")
-					?? ""
-				)\(try standardErrorPipe.fileHandleForReading // swiftformat:enable indent
-					.readToEnd()
-					.flatMap { String(data: $0, encoding: .utf8) }?
-					.trimmingCharacters(in: .whitespacesAndNewlines)
-					.prependIfNotEmpty("\n\nStandard error:\n")
-					?? "" // swiftformat:disable:this wrap
-				)
-				""",
-			)
-		}
+		_ = try await run(
+			"/usr/bin/mdimport",
+			appFolderURL.path(percentEncoded: false),
+			errorMessage: "Failed to \(action) \(appNameAndVersion) from \(pkgHardLinkPath)",
+		)
 
 		LSRegisterURL(appFolderURL as NSURL, true) // swiftlint:disable:this legacy_objc_type
 	}
-
-	private func installPkg(appNameAndVersion: String) throws -> URL {
-		guard let pkgHardLinkPath = pkgHardLinkURL?.path(percentEncoded: false) else {
-			throw MASError.error("Failed to find pkg to \(action) \(appNameAndVersion)")
-		}
-
-		let process = Process()
-		process.executableURL = URL(filePath: "/usr/sbin/installer", directoryHint: .notDirectory)
-		process.arguments = ["-dumplog", "-pkg", pkgHardLinkPath, "-target", "/"]
-		let standardOutputPipe = Pipe()
-		process.standardOutput = standardOutputPipe
-		let standardErrorPipe = Pipe()
-		process.standardError = standardErrorPipe
-		do {
-			try run(asEffectiveUID: 0, andEffectiveGID: 0) { try process.run() }
-		} catch {
-			throw MASError.error("Failed to \(action) \(appNameAndVersion) from \(pkgHardLinkPath)", error: error)
-		}
-		process.waitUntilExit()
-		let standardOutputText =
-			try standardOutputPipe.fileHandleForReading.readToEnd().flatMap { String(data: $0, encoding: .utf8) } ?? ""
-		let standardErrorText =
-			try standardErrorPipe.fileHandleForReading.readToEnd().flatMap { String(data: $0, encoding: .utf8) } ?? ""
-		guard process.terminationStatus == 0 else {
-			throw MASError.error(
-				"""
-				Failed to \(action) \(appNameAndVersion) from \(pkgHardLinkPath)
-				Exit status: \(process.terminationStatus)\(
-					standardOutputText.trimmingCharacters(in: .whitespacesAndNewlines).prependIfNotEmpty("\n\nStandard output:\n")
-				)\(standardErrorText.trimmingCharacters(in: .whitespacesAndNewlines).prependIfNotEmpty("\n\nStandard error:\n"))
-				""",
-			)
-		}
-		guard
-			let appFolderURLSubstring = standardErrorText
-			.matches(of: unsafe appFolderURLRegex)
-			.compactMap(\.1)
-			.min(by: { $0.count < $1.count })
-		else {
-			throw MASError.error(
-				"Failed to find app folder URL in installer output for \(appNameAndVersion)",
-				error: standardErrorText,
-			)
-		}
-		guard let appFolderURL = URL(string: String(appFolderURLSubstring)) else {
-			throw MASError.error(
-				"Failed to parse app folder URL for \(appNameAndVersion) from \(appFolderURLSubstring)",
-				error: standardErrorText,
-			)
-		}
-
-		return appFolderURL
-	}
 }
 
 private struct DownloadSnapshot: Sendable { // swiftlint:disable:this one_declaration_per_file
@@ -500,10 +442,6 @@ private extension String {
 	var capitalizingFirstCharacter: Self {
 		prefix(1).capitalized + dropFirst()
 	}
-
-	func prependIfNotEmpty(_ prefix: String) -> Self {
-		isEmpty ? self : prefix + self
-	}
 }
 
 private extension URL {

Sources/mas/Utilities/Pipe.swift

@@ -0,0 +1,14 @@
+//
+// Pipe.swift
+// mas
+//
+// Copyright © 2025 mas-cli. All rights reserved.
+//
+
+internal import Foundation
+
+extension Pipe {
+	func readToEnd(encoding: String.Encoding = .utf8) throws -> String? {
+		try fileHandleForReading.readToEnd().flatMap { String(data: $0, encoding: encoding) }
+	}
+}

Sources/mas/Utilities/Process.swift

@@ -0,0 +1,62 @@
+//
+// Process.swift
+// mas
+//
+// Copyright © 2025 mas-cli. All rights reserved.
+//
+
+internal import Foundation
+private import ObjectiveC
+
+func run(
+	_ executablePath: String,
+	_ args: String...,
+	errorMessage: @autoclosure () -> String,
+	runProcess run: (Process) throws -> Void = { try $0.run() },
+) async throws -> (standardOutputString: String, standardErrorString: String) {
+	let process = Process()
+	process.executableURL = URL(filePath: executablePath, directoryHint: .notDirectory)
+	process.arguments = args
+
+	let standardOutputPipe = Pipe()
+	let standardErrorPipe = Pipe()
+
+	process.standardOutput = standardOutputPipe
+	process.standardError = standardErrorPipe
+
+	let standardOutputTask = Task(priority: .background) {
+		try standardOutputPipe.readToEnd()?.trimmingCharacters(in: .whitespacesAndNewlines) ?? ""
+	}
+	let standardErrorTask = Task(priority: .background) {
+		try standardErrorPipe.readToEnd()?.trimmingCharacters(in: .whitespacesAndNewlines) ?? ""
+	}
+
+	do {
+		try run(process)
+	} catch {
+		throw MASError.error(errorMessage(), error: error)
+	}
+	process.waitUntilExit()
+
+	let standardOutputString = try await standardOutputTask.value
+	let standardErrorString = try await standardErrorTask.value
+
+	guard process.terminationStatus == 0 else {
+		throw MASError.error(
+			"""
+			\(errorMessage())
+			Exit status: \(process.terminationStatus)\
+			\(standardOutputString.ifNotEmptyPrepend("\n\nStandard output:\n"))\
+			\(standardErrorString.ifNotEmptyPrepend("\n\nStandard error:\n"))
+			""",
+		)
+	}
+
+	return (standardOutputString, standardErrorString)
+}
+
+private extension String {
+	func ifNotEmptyPrepend(_ prefix: String) -> Self {
+		isEmpty ? self : prefix + self
+	}
+}

Tests/MASTests/Utilities/Consequences.swift

@@ -6,6 +6,7 @@
 //
 
 internal import Foundation
+@testable private import mas
 
 struct Consequences<Value> {
 	let value: Value?
@@ -88,11 +89,8 @@ private struct StandardStreamCapture { // swiftlint:disable:this one_declaration
 		close(outDuplicateFD)
 		close(errDuplicateFD)
 
-		return ( // swiftlint:disable:next force_try
-			try! outPipe.fileHandleForReading.readToEnd().flatMap { String(data: $0, encoding: encoding) } ?? "",
-			try! errPipe.fileHandleForReading.readToEnd().flatMap { String(data: $0, encoding: encoding) } ?? "",
-		) // swiftlint:disable:previous force_try
-	}
+		return (try! outPipe.readToEnd(encoding: encoding) ?? "", try! errPipe.readToEnd(encoding: encoding) ?? "")
+	} // swiftlint:disable:previous force_try
 }
 
 enum NoValue: Equatable { // swiftlint:disable:this one_declaration_per_file