Fix: Filter synthetic identifiers from outer scope derives #1953
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This fixes a bug where synthetic identifiers created by ClosureTransformer were leaking into derive calls in outer scopes, causing ReferenceError at runtime. The fix adds heuristic filtering in filterRelevantDataFlows() to detect when synthetic identifiers (those without symbol information) are being incorrectly included in outer-scope expressions. The heuristic: - Identifies synthetic vs non-synthetic dataflows by checking for symbol info - When mixing both: if non-synthetic flows all have outer-scope symbols (2+), we're at outer scope → filter synthetic ones - Otherwise we're inside a callback with captures → keep everything This approach is robust as it relies on symbol presence rather than hardcoded identifier names, so it won't break if user code happens to use variables named "element", "index", etc. Also adds test case for nested map within conditional to prevent regression and updates expected output for map-nested-conditional to correctly derive element properties. 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude <noreply@anthropic.com>
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1 issue found across 3 files
Prompt for AI agents (all 1 issues)
Understand the root cause of the following 1 issues and fix them.
<file name="packages/ts-transformers/src/transformers/opaque-ref/helpers.ts">
<violation number="1" location="packages/ts-transformers/src/transformers/opaque-ref/helpers.ts:152">
This heuristic treats callbacks that capture multiple outer variables as outer-scope expressions, so it drops the synthetic map parameter data flows; when a callback references two captured identifiers plus the synthetic parameter, the synthetic flow is removed and the derive call breaks.</violation>
</file>
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…e captures
The heuristic for filtering synthetic dataflows was too aggressive. It
treated callbacks that capture 2+ outer variables as outer-scope
expressions, which caused it to drop synthetic map parameter dataflows.
This broke derive calls when a callback referenced multiple captured
identifiers plus the synthetic parameter.
Example that was breaking:
```tsx
items.map((item, index) => (
<div>
{item.name} - {cell1.value} - {cell2.value} - {index}
</div>
))
```
The heuristic saw 2 outer-scope symbols (cell1, cell2) and incorrectly
filtered out the synthetic parameters (item, index).
Fix:
- Check if dataflows belong to a map callback scope before applying
the "2+ outer captures" heuristic
- If in a map callback scope, keep all dataflows (synthetic and captures)
- Only filter out ignored parameters
- This allows callbacks to legitimately capture multiple outer variables
while still using synthetic map parameters
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>
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This fixes a bug where synthetic identifiers created by ClosureTransformer were leaking into derive calls in outer scopes, causing ReferenceError at runtime.
The fix adds heuristic filtering in filterRelevantDataFlows() to detect when synthetic identifiers (those without symbol information) are being incorrectly included in outer-scope expressions. The heuristic:
This approach is robust as it relies on symbol presence rather than hardcoded identifier names, so it won't break if user code happens to use variables named "element", "index", etc.
Also adds test case for nested map within conditional to prevent regression and updates expected output for map-nested-conditional to correctly derive element properties.
🤖 Generated with Claude Code
Summary by cubic
Fixes a runtime ReferenceError caused by synthetic identifiers leaking into outer-scope derive calls in nested map scenarios. Adds a heuristic to filter these synthetic params when analyzing outer scope.