iOS: reject instead of crashing when an upload's file is missing

CHANGELOG.md

@@ -1,3 +1,12 @@
+## 9.0.1
+
+Fixed:
+- **iOS no longer crashes when an upload's file is missing.** A background
+  session raises an Objective-C exception, not an error, when it cannot read
+  the file, and Swift cannot catch it. A file deleted after the caller checked
+  it ended the app. `startUpload` now rejects instead, and a chunked part that
+  cannot be enqueued journals an `error` with `errorKind: 'file'`.
+
 ## 9.0.0
 
 Chunked uploads move into the library: one file, many part requests, one upload

ios/ChunkedCoordinator.swift

@@ -498,7 +498,15 @@ final class ChunkedCoordinator {
       request.setValue(value, forHTTPHeaderField: key)
     }
     let session = uploader.session(wifiOnly: manifest.wifiOnly)
-    let task = session.uploadTask(with: request, fromFile: partFile)
+    let task: URLSessionUploadTask
+    do {
+      task = try RNBackgroundUpload.uploadTask(session, request, fromFile: partFile)
+    } catch {
+      stall(id, entry: errorEntry(
+        id: id, error: "cannot enqueue part \(index): \(error.localizedDescription)",
+        errorKind: "file", partIndex: index))
+      return false
+    }
     task.taskDescription = ChunkedEngine.taskDescription(
       id: id, part: index, incarnation: manifest.incarnation)
     let key = TaskMap.key(session, task)

ios/RNBGUCatchException.h

@@ -0,0 +1,15 @@
+#import <Foundation/Foundation.h>
+
+// Swift cannot catch an Objective-C exception. One that unwinds through a Swift
+// frame ends the process. This runs `block` in an Objective-C @try and hands the
+// exception back to Swift as a value.
+//
+// Keep this header Foundation-only. It is public, so it is part of the module
+// umbrella that this module's Swift and plain Obj-C consumers both import.
+
+NS_ASSUME_NONNULL_BEGIN
+
+/// Runs `block`. Returns the exception it raised, or nil when it returned.
+FOUNDATION_EXPORT NSException *_Nullable RNBGUCatchException(NS_NOESCAPE void (^block)(void));
+
+NS_ASSUME_NONNULL_END

ios/RNBGUCatchException.m

@@ -0,0 +1,11 @@
+#import "RNBGUCatchException.h"
+
+NSException *_Nullable RNBGUCatchException(NS_NOESCAPE void (^block)(void))
+{
+  @try {
+    block();
+    return nil;
+  } @catch (NSException *exception) {
+    return exception;
+  }
+}

ios/RNBackgroundUpload.swift

@@ -50,13 +50,14 @@ public class RNBackgroundUpload: NSObject, URLSessionDataDelegate {
   // removeUpload cancels work with no user-cancel mark.
   private static var removedIds = Set<String>()
   // The consumer-supplied ids whose check-and-create is in flight, mapped to
-  // the resolves of the concurrent same-id calls. The existence check
+  // the promises of the concurrent same-id calls. The existence check
   // enumerates the session tasks asynchronously. Without this claim, two
   // concurrent calls could both see "no task" and enqueue duplicates. The id
   // is claimed synchronously, under `lock`, BEFORE the enumeration is
   // dispatched. The map entry drains when the first caller's create-or-find
-  // lands.
-  private static var creationsInFlight: [String: [RCTPromiseResolveBlock]] = [:]
+  // lands, and every parked call gets that caller's outcome.
+  private static var creationsInFlight:
+    [String: [(resolve: RCTPromiseResolveBlock, reject: RCTPromiseRejectBlock)]] = [:]
 
   private static var backgroundSession: URLSession?
   private static var wifiOnlySession: URLSession?
@@ -249,8 +250,8 @@ public class RNBackgroundUpload: NSObject, URLSessionDataDelegate {
     let fileURL = URL(string: path) ?? URL(fileURLWithPath: path)
 
     let session = self.session(wifiOnly: wifiOnly)
-    let startNew = {
-      let task = session.uploadTask(with: request, fromFile: fileURL)
+    let startNew: () throws -> Void = {
+      let task = try RNBackgroundUpload.uploadTask(session, request, fromFile: fileURL)
       task.taskDescription = uploadId
       TaskMap.set(TaskMap.Meta(id: uploadId, accept: accept, partIndex: nil),
                   forKey: self.taskMapKey(session, task))
@@ -265,30 +266,39 @@ public class RNBackgroundUpload: NSObject, URLSessionDataDelegate {
     // session. A generated id cannot collide, so that path does not do the
     // (asynchronous) task enumeration.
     guard options["id"] != nil else {
-      startNew()
-      resolve(uploadId)
+      do {
+        try startNew()
+        resolve(uploadId)
+      } catch {
+        reject("RN Uploader", error.localizedDescription, error)
+      }
       return
     }
 
     // Serialize the check-and-create for each id: claim the id synchronously,
     // before we dispatch the enumeration. The first caller runs the check and
-    // creates the task. A concurrent same-id caller parks its resolve here.
-    // When the task lands, we answer the parked calls with the id. There is no
-    // second task, and there is no polling.
+    // creates the task. A concurrent same-id caller parks its promise here.
+    // When the task lands, we answer the parked calls with the same outcome.
+    // There is no second task, and there is no polling.
     RNBackgroundUpload.lock.lock()
     if RNBackgroundUpload.creationsInFlight[uploadId] != nil {
-      RNBackgroundUpload.creationsInFlight[uploadId]?.append(resolve)
+      RNBackgroundUpload.creationsInFlight[uploadId]?.append((resolve: resolve, reject: reject))
       RNBackgroundUpload.lock.unlock()
       return
     }
     RNBackgroundUpload.creationsInFlight[uploadId] = []
     RNBackgroundUpload.lock.unlock()
-    let settle = {
+    let settle = { (failure: Error?) in
       RNBackgroundUpload.lock.lock()
       let waiters = RNBackgroundUpload.creationsInFlight.removeValue(forKey: uploadId) ?? []
       RNBackgroundUpload.lock.unlock()
-      resolve(uploadId)
-      for waiter in waiters { waiter(uploadId) }
+      for call in [(resolve: resolve, reject: reject)] + waiters {
+        if let failure {
+          call.reject("RN Uploader", failure.localizedDescription, failure)
+        } else {
+          call.resolve(uploadId)
+        }
+      }
     }
 
     let group = DispatchGroup()
@@ -308,8 +318,12 @@ public class RNBackgroundUpload: NSObject, URLSessionDataDelegate {
       }
     }
     group.notify(queue: .main) {
-      if !exists { startNew() }
-      settle()
+      do {
+        if !exists { try startNew() }
+        settle(nil)
+      } catch {
+        settle(error)
+      }
     }
   }
 
@@ -696,6 +710,23 @@ public class RNBackgroundUpload: NSObject, URLSessionDataDelegate {
     if let handler { DispatchQueue.main.async { handler() } }
   }
 
+  // A background session raises an NSException, not an error, when the file
+  // cannot be read: for example, when the file was deleted after the caller
+  // checked it. Uncaught, the exception ends the process. This throws a
+  // URL-domain error instead, which errorKind(for:) classifies as 'file'.
+  static func uploadTask(_ session: URLSession, _ request: URLRequest,
+                         fromFile file: URL) throws -> URLSessionUploadTask {
+    var task: URLSessionUploadTask?
+    if let exception = RNBGUCatchException({
+      task = session.uploadTask(with: request, fromFile: file)
+    }) {
+      throw NSError(domain: NSURLErrorDomain, code: NSURLErrorCannotOpenFile, userInfo: [
+        NSLocalizedDescriptionKey: exception.reason ?? "Cannot read file at \(file.absoluteString)",
+      ])
+    }
+    return task!
+  }
+
   // Classify a transport error to match Android's errorKind taxonomy: a missing or
   // unreadable source file -> 'file'; other URL-domain errors -> 'network'; anything
   // else -> 'unknown'. It is internal because the chunked coordinator also

package.json

@@ -1,6 +1,6 @@
 {
   "name": "react-native-background-upload",
-  "version": "9.0.0",
+  "version": "9.0.1",
   "description": "Cross platform http post file uploader with android and iOS background support",
   "main": "src/index",
   "typings": "src/index.ts",

react-native-background-upload.podspec

@@ -16,10 +16,12 @@ Pod::Spec.new do |s|
 
   s.source_files = "ios/**/*.{h,m,mm,swift}"
   # RNFileUploader.h imports the codegen spec header, which is Obj-C++ only. Keep
-  # every header out of the public umbrella so a consumer's plain Obj-C
+  # it out of the public umbrella so a consumer's plain Obj-C
   # `@import react_native_background_upload;` still compiles — that import is how
   # the AppDelegate reaches RNBackgroundUpload's background-session handler.
-  s.private_header_files = "ios/**/*.h"
+  s.private_header_files = "ios/RNFileUploader.h"
+  # Foundation-only, and public so that the Swift half of the module can see it.
+  s.public_header_files = "ios/RNBGUCatchException.h"
 
   s.platform = :ios, "15.1"
   s.swift_version = "5.0"