Fix simulator putfile posix error

FirebaseStorage/CHANGELOG.md

@@ -1,4 +1,7 @@
 # Unreleased
+- [fixed] Fixed an issue where `putFile` could fail on the iOS Simulator with `POSIX errno 40`
+  (`EMSGSIZE`) due to a QUIC bug in background sessions, and improved error formatting
+  for `NSPOSIXErrorDomain` errors. (#16351)
 - [fixed] Fixed a race condition in Storage task cancellation and improved Swift 6 strict
   concurrency compliance for `StorageTask`. (#16353)
 - [fixed] Fixed a crash that could occur when parsing malformed `gs://` URLs, and improved

FirebaseStorage/Sources/Internal/StorageFetcherService.swift

@@ -63,6 +63,11 @@ actor StorageFetcherService {
     if let _fetcherService {
       _fetcherService.testBlock = testBlock
     }
+    for (_, bucketMap) in fetcherServiceMap {
+      for (_, fetcherService) in bucketMap {
+        fetcherService.testBlock = testBlock
+      }
+    }
   }
 
   private var testBlock: GTMSessionFetcherTestBlock?

FirebaseStorage/Sources/StorageError.swift

@@ -77,9 +77,17 @@ public let StorageErrorDomain: String = "FIRStorageErrorDomain"
     case 404: StorageError.objectNotFound(
         object: ref.path.object ?? "<object-entity-internal-error>", serverError: errorDictionary
       )
-    default: StorageError.unknown(
-        message: "Unexpected \(serverError.code) code from backend", serverError: errorDictionary
-      )
+    default:
+      if serverError.domain == NSPOSIXErrorDomain {
+        StorageError.unknown(
+          message: "POSIX errno \(serverError.code) (\(String(cString: strerror(Int32(truncatingIfNeeded: serverError.code)))))",
+          serverError: errorDictionary
+        )
+      } else {
+        StorageError.unknown(
+          message: "Unexpected \(serverError.code) code from backend", serverError: errorDictionary
+        )
+      }
     }
     return storageError as NSError
   }

FirebaseStorage/Sources/StorageUploadTask.swift

@@ -112,7 +112,12 @@ import Foundation
           uploadFetcher.uploadFileURL = fileURL
           uploadFetcher.comment = "File UploadTask"
 
-          if !GULAppEnvironmentUtil.supportsBackgroundURLSessionUploads() {
+          #if targetEnvironment(simulator)
+            let supportsBackground = false
+          #else
+            let supportsBackground = GULAppEnvironmentUtil.supportsBackgroundURLSessionUploads()
+          #endif
+          if !supportsBackground {
             uploadFetcher.useBackgroundSession = false
           }
         }

FirebaseStorage/Tests/Integration/StoragePOSIXErrorTest.swift

@@ -0,0 +1,44 @@
+// Copyright 2026 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+@testable import FirebaseStorage
+import Foundation
+#if COCOAPODS
+  import GTMSessionFetcher
+#else
+  import GTMSessionFetcherCore
+#endif
+import XCTest
+
+@available(iOS 13.0, macOS 10.15, macCatalyst 13.0, tvOS 13.0, watchOS 6.0, *)
+class StoragePOSIXErrorTest: StorageIntegrationCommon {
+  func testPutFileWithPOSIXError40() async throws {
+    let ref = storage.reference(withPath: "ios/public/testPOSIX40")
+
+    let data = try XCTUnwrap("Hello".data(using: .utf8))
+    let tmpDirURL = URL(fileURLWithPath: NSTemporaryDirectory())
+    let fileURL = tmpDirURL.appendingPathComponent(#function + "hello.txt")
+    try data.write(to: fileURL, options: .atomicWrite)
+    defer {
+      try? FileManager.default.removeItem(at: fileURL)
+    }
+
+    do {
+      let metadata = try await ref.putFileAsync(from: fileURL)
+      XCTAssertEqual(metadata.size, Int64(data.count))
+    } catch {
+      XCTFail("Unexpected failure: \(error)")
+    }
+  }
+}