Fix Race conditions

[biovolt]

I believe this fixes https://github.com/SDWebImage/SDWebImageSwiftUI/issues/358

Summary by CodeRabbit

• Bug Fixes
  • Improves stability of image loading by ensuring progress and completion callbacks are invoked consistently under concurrent scenarios.
  • Delivers progress updates reliably on the main thread, reducing missed or duplicated notifications.
  • Reduces rare race-related crashes or hangs during rapid callback changes.
• Refactor
  • Internally synchronizes callback handling for more predictable behavior, with no changes to how you set or use callbacks.

[coderabbitai[bot]]

Walkthrough

Introduces thread-safe storage and invocation for image loading callbacks in ImageManager by adding a private callback queue and backing closures. Public callback properties become computed with synchronized get/set. Progress and completion now capture local callback references and dispatch to the main thread, minimizing race conditions. No functional flow changes.

Changes

Cohort / File(s)	Summary of Changes
Thread-safe callback handling SDWebImageSwiftUI/Classes/ImageManager.swift	- Added callbackQueue and private _successBlock, _failureBlock, _progressBlock. - Converted successBlock, failureBlock, progressBlock to computed properties synchronized via callbackQueue. - Captured local callback copies for progress/completion before invoking on main thread. - Maintains existing loading flow and API surface behavior.

Sequence Diagram(s)

sequenceDiagram
  autonumber
  participant View
  participant ImageManager
  participant SDWebImage
  participant CallbackQueue as Callback Queue
  participant MainThread

  View->>ImageManager: set success/failure/progress blocks
  ImageManager->>CallbackQueue: sync set _success/_failure/_progress

  View->>ImageManager: load(url)
  ImageManager->>SDWebImage: start request

  SDWebImage-->>ImageManager: progress(received,total)
  ImageManager->>CallbackQueue: sync get _progress
  CallbackQueue-->>ImageManager: progressCallback
  alt progressCallback exists
    ImageManager->>MainThread: invoke progressCallback(received,total)
  end

  SDWebImage-->>ImageManager: completion(image,data,cacheType or error)
  ImageManager->>CallbackQueue: sync get _success/_failure
  CallbackQueue-->>ImageManager: successCallback/failureCallback
  alt success
    ImageManager->>MainThread: invoke successCallback(image,data,cacheType)
  else failure
    ImageManager->>MainThread: invoke failureCallback(error)
  end

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Poem

In burrows of bytes, I twitch with delight,
Queued little callbacks, kept snug and tight.
No races to chase, no hare-brained despair—
Progress hops softly, completion with care.
On the main meadow, we nuzzle the view,
Thread-safe thumps: thump-thump—swift and true.

✨ Finishing Touches

• [ ] 📝 Generate Docstrings

🧪 Generate unit tests

• [ ] Create PR with unit tests
• [ ] Post copyable unit tests in a comment

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