Fix uid duplication during paste

[bkrmendy]

Problem

Pasting into slots might introduce duplicate uids into projects

Root cause

When an element is pasted, we first look for a target parent, and then "fix" the uids of the pasted elements (to avoid duplicate uids). However, if an element is pasted into a slot, we need to pre-generate a uid for the fragment the pasted element might be wrapped into. The uid of this fragment wrapper might clash with one of the new uids generated during the fixing process.

The reason this only came out now is that

• pasting into a slot with a fragment wrapper is an edge case in itself (since it only happens when the content of a slot goes from a single child to multiple children)
• the fragment uid is generated from a UUID() call, while the new uids of the pasted elements are deterministically generated based on the uids already present in the project, and the test project is very small, so it's very unlikely that an already-existing uid would be generated

Fix

When initializing the mapping for new uids (fixedUIDMappingNewUIDS), consider the uid of the fragment wrapper (if one is used).

[github-actions]

Try me

[relativeci]

Job #10219: Bundle Size — 62.35MiB (~+0.01%).

a33dfdf(current) vs 794431b master#10213(baseline)

Warning

Bundle contains 66 duplicate packages – View duplicate packages

Bundle metrics   1 change 1 regression

	Current Job #10219	Baseline Job #10213
Initial JS	35.39MiB(~+0.01%)	35.38MiB
Initial CSS	0B	0B
Cache Invalidation	21.79%	21.79%
Chunks	28	28
Assets	32	32
Modules	4407	4407
Duplicate Modules	490	490
Duplicate Code	30.7%	30.7%
Packages	462	462
Duplicate Packages	65	65

Bundle size by type   2 changes 1 regression 1 improvement

	Current Job #10219	Baseline Job #10213
JS	62.34MiB (~+0.01%)	62.33MiB
HTML	11.37KiB (-0.32%)	11.41KiB

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View job #10219 report View fix/static-reparent-wrapper-uid-... branch activity View project dashboard

[github-actions]

Performance test results: