From 04cf52d23a363baf3a54331a7aa6f14c65b9dda6 Mon Sep 17 00:00:00 2001
From: Alex Hoppen <ahoppen@apple.com>
Date: Fri, 8 Sep 2023 09:46:35 -0700
Subject: [PATCH] Support cancellation of subcommands in
 `swift-syntax-dev-utils` using Ctrl-C
MIME-Version: 1.0
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It’s really quite unfortunate that we need to do all this handling ourselves…
---
 .../SwiftSyntaxDevUtils.swift                 | 14 +++++++++++
 .../common/ProcessRunner.swift                | 25 +++++++++++++++++++
 2 files changed, 39 insertions(+)

diff --git a/SwiftSyntaxDevUtils/Sources/swift-syntax-dev-utils/SwiftSyntaxDevUtils.swift b/SwiftSyntaxDevUtils/Sources/swift-syntax-dev-utils/SwiftSyntaxDevUtils.swift
index 85209c9bfad..c1988f67cde 100644
--- a/SwiftSyntaxDevUtils/Sources/swift-syntax-dev-utils/SwiftSyntaxDevUtils.swift
+++ b/SwiftSyntaxDevUtils/Sources/swift-syntax-dev-utils/SwiftSyntaxDevUtils.swift
@@ -31,4 +31,18 @@ struct SwiftSyntaxDevUtils: ParsableCommand {
       VerifySourceCode.self,
     ]
   )
+
+  public static func main() {
+    SigIntListener.registerSigIntSubprocessTerminationHandler()
+    do {
+      var command = try parseAsRoot(nil)
+      try command.run()
+    } catch {
+      if !SigIntListener.hasReceivedSigInt {
+        // No point printing an error message if the user requested the termination
+        // of the script.
+        exit(withError: error)
+      }
+    }
+  }
 }
diff --git a/SwiftSyntaxDevUtils/Sources/swift-syntax-dev-utils/common/ProcessRunner.swift b/SwiftSyntaxDevUtils/Sources/swift-syntax-dev-utils/common/ProcessRunner.swift
index e20b600997e..247f4150a0f 100644
--- a/SwiftSyntaxDevUtils/Sources/swift-syntax-dev-utils/common/ProcessRunner.swift
+++ b/SwiftSyntaxDevUtils/Sources/swift-syntax-dev-utils/common/ProcessRunner.swift
@@ -12,6 +12,29 @@
 
 import Foundation
 
+/// Keeps track of subprocesses spawned by this script and forwards SIGINT
+/// signals to them.
+class SigIntListener {
+  /// The subprocesses spawned by this script that are currently running.
+  static var runningSubprocesses: Set<Process> = []
+
+  /// Whether a `SIGINT` signal has been received by this script.
+  static var hasReceivedSigInt: Bool = false
+
+  /// Registers a `SIGINT` signal handler that forwards `SIGINT` to all
+  /// subprocesses that are registered in `runningSubprocesses`
+  static func registerSigIntSubprocessTerminationHandler() {
+    #if canImport(Darwin) || canImport(Glibc)
+    signal(SIGINT) { _ in
+      SigIntListener.hasReceivedSigInt = true
+      for process in SigIntListener.runningSubprocesses {
+        process.interrupt()
+      }
+    }
+    #endif
+  }
+}
+
 /// Provides convenience APIs for launching and gathering output from a subprocess
 public class ProcessRunner {
   private static let serialQueue = DispatchQueue(label: "\(ProcessRunner.self)")
@@ -56,7 +79,9 @@ public class ProcessRunner {
     }
 
     try process.run()
+    SigIntListener.runningSubprocesses.insert(process)
     process.waitUntilExit()
+    SigIntListener.runningSubprocesses.remove(process)
     if captureStdout || captureStderr {
       // Make sure we've received all stdout/stderr
       group.wait()