Feat: forbid tasks on WebGL

[NickKhalow]

Context / Problem
DOTween exposes async/Task-based instructions when targeting .NET 4.6+ / .NET Standard 2.0.
On WebGL, Task-based async APIs are not supported in a meaningful or safe way due to the single-threaded execution model and lack of real threading. This leads to silent hangs or undefined behavior rather than explicit failures.

What was changed

• Excluded DOTween async instructions from compilation on UNITY_WEBGL.

• Added !UNITY_WEBGL to the existing preprocessor guards for async-related code paths.

• Applied consistently across:

  • UnityExamples
  • UnityTests (multiple Unity versions)
  • Prebuilt DOTween assembly sources

Why this approach

• Enforces correctness at compile time, not runtime.
• Prevents accidental usage of unsupported async APIs on WebGL.
• Aligns with WebGL platform constraints and avoids silent runtime failures.

Impact

• No behavior change for non-WebGL platforms.
• On WebGL, async/Task-based DOTween APIs are no longer available, making platform limitations explicit.

Risk
Low. Change is limited to conditional compilation and does not affect runtime logic on supported platforms.

[Demigiant]

Ahoy Nick,

Apologies if it took me a while to get back to you, but I was both finishing some other DOTween stuff and unsure if this merge made sense. As far as I know, and can see in the documentation, only Task.Delay doesn't work in WebGL, and DOTween doesn't use it. To be on the safe side I made a test, which you can see here, and DOTween's AsyncWaitForCompletion (which works like DOTween's other async methods via Task.Yield) works correctly.

Let me know if I missed something, and cheers,
Daniele

[NickKhalow]

Hey, Daniele

The concern isn’t whether Task.Yield works today.
The concern is that allowing Task-based async in WebGL expands the semantic surface to constructs that WebGL cannot guarantee (blocking, timers, threading assumptions).
Even if DOTween currently uses only Yield, keeping Tasks namespace out of WebGL builds preserves a stricter invariant and reduces future misuse risk.

Best, Nick