Open Radar

 
Summary:
It says:
"If your block returns true, Photos provides the original asset data for editing."

That's incorrect. For example:
1. I edited the original image(i0) using App A, get result image i1.
2. I then edited the image using another App B. Suppose App B doesn't support App A's PHAdjustmentData. What App B get as input is i1. No problem, since canHandleAdjustmentData returns false so it should get i1. The editing result is i2.
3. I then open the image again in App B. This time canHandleAdjustmentData returns true, so according to the doc it should get i0 with PHAdjustmentData based on i1. This mixture doesn't make sense. Luckily, that's not what really happens. What really happens is it gets i1 with PHAdjustmentData based on i1. Great. So the mistake is in the doc.

In contrast, the doc of PHContentEditingController.canHandle(_: PHAdjustmentData) says:
"If you return true from this method, Photos provides the previous asset version for editing."
which is correct.