[hl662]

TL;DR

MapLayerManagerDragDrop.test.tsx fails intermittently in CI under load. The cause is in the test's mock: React's dev build calls component functions with no props when it builds component stacks for warnings, and the DragDropProvider mock saved those undefined props over the real ones. The mock now ignores those calls, and the test skipped for #1796 is re-enabled.

Fixes #1796

Why

The setup helper renderMapLayerManager checks that the mocked DragDropProvider received its props (line 84). That check failed at random in CI: in both runs linked from #1796, and in four CI runs on #1826/#1828 this week. #1797 skipped the first test, but the failure just moved to whichever test ran first, because the problem was in the shared setup, not in the drag behavior.

The failure sequence:

1. render() mounts MapLayerManager, and the mock saves the provider's props.
2. During the one-tick flush that follows, an async state update in MapLayerManager lands outside act(), so React logs the "not wrapped in act(...)" warning. The package's vitest config hides that warning from the console.
3. To build the warning's component stack, React's dev build (describeNativeComponentFrame) calls each component in the tree with no arguments. The mock runs again and saves props === undefined.

Step 2 depends on timing, which is why the test failed under CI load but passed locally.

What

Change	Why
The DragDropProvider mock only saves props when it receives them	Calls React makes only to build component stacks no longer overwrite the saved props
Re-enable restores the drag-start layer order when the pointer leaves all droppables	It failed the same way at the same setup line, so this fix covers it too

Testing

Reproduction and validation

To make the flake show up reliably, I ran 30 copies of the test file in one vitest run with coverage, --maxWorkers=8, and every CPU core saturated by yes processes.

Scenario	Result
Before the fix	1–2 of 30 files failed per run, all at line 84
With temporary logging on the mock	Showed the third provider call coming from describeNativeComponentFrame, setting undefined
With the fix and the re-enabled test, 10 runs (300 files, 900 tests)	0 failures
Fix removed, re-enabled test kept, 4 runs	Failed again (2 of 120 files)
vitest --run --coverage for map-layers	11 files, 83 passed, 1 skipped (unrelated)
pnpm lint for map-layers	No problems

This is a test-only change, so there's no changeset.

Nambot 🤖 (powered by claude-opus-5.5)

[Copilot]

🟢 Approval recommended

The narrow, test-only fix addresses the reported failure with no unresolved findings.

0 open findings

What changed in this PR

Fixes the map-layers test setup flake behind #1796 without changing production behavior.

Changes:

• Preserves captured provider props during React’s diagnostic calls without props.
• Re-enables the skipped drag-order restoration test.

File	Description
packages/​map-layers/​src/​test/​MapLayerManagerDragDrop.test.tsx	Guards mock props capture and restores the skipped test.

🧠 Review effort: Balanced

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