asyncBoot will no longer try booting server again if it is already bo…

…oted (#3195)

Sources/Vapor/Application.swift

@@ -247,12 +247,15 @@ public final class Application: Sendable {
 
     /// Called when the applications starts up, will trigger the lifecycle handlers. The asynchronous version of ``boot()``
     public func asyncBoot() async throws {
-        self.isBooted.withLockedValue { booted in
-            guard !booted else {
-                return
-            }
-            booted = true
+        /// Skip the boot process if already booted
+        guard !self.isBooted.withLockedValue({
+            var result = true
+            swap(&$0, &result)
+            return result
+        }) else {
+            return
         }
+
         for handler in self.lifecycle.handlers {
             try await handler.willBootAsync(self)
         }

Tests/VaporTests/ApplicationTests.swift

@@ -169,6 +169,47 @@ final class ApplicationTests: XCTestCase {
         XCTAssertEqual(foo.didBootAsyncFlag.withLockedValue({ $0 }), true)
         XCTAssertEqual(foo.shutdownAsyncFlag.withLockedValue({ $0 }), true)
     }
+
+    func testBootDoesNotTriggerLifecycleHandlerMultipleTimes() throws {
+        let app = Application(.testing)
+        defer { app.shutdown() }
+
+        final class Handler: LifecycleHandler, Sendable {
+            let bootCount = NIOLockedValueBox(0)
+            func willBoot(_ application: Application) throws {
+                bootCount.withLockedValue { $0 += 1 }
+            }
+        }
+
+        let handler = Handler()
+        app.lifecycle.use(handler)
+
+        try app.boot()
+        try app.boot()
+
+        XCTAssertEqual(handler.bootCount.withLockedValue({ $0 }), 1)
+    }
+
+    func testAsyncBootDoesNotTriggerLifecycleHandlerMultipleTimes() async throws {
+        let app = try await Application.make(.testing)
+
+        final class Handler: LifecycleHandler, Sendable {
+            let bootCount = NIOLockedValueBox(0)
+            func willBoot(_ application: Application) throws {
+                bootCount.withLockedValue { $0 += 1 }
+            }
+        }
+
+        let handler = Handler()
+        app.lifecycle.use(handler)
+
+        try await app.asyncBoot()
+        try await app.asyncBoot()
+
+        XCTAssertEqual(handler.bootCount.withLockedValue({ $0 }), 1)
+
+        try await app.asyncShutdown()
+    }
 
     func testThrowDoesNotCrash() throws {
         enum Static {