Hamidreza Hanafi 9c96937329 fix(transpiler): preserve simplified property values in object spread expressions (#25401) ...

Fixes #25398

### What does this PR do?

Fixes a bug where object expressions with spread properties and nullish
coalescing to empty objects (e.g., `k?.x ?? {}`) would produce invalid
JavaScript output like `k?.x ?? ` (missing `{}`).

### Root Cause

In `src/ast/SideEffects.zig`, the `simplifyUnusedExpr` function handles
unused object expressions with spread properties. When simplifying
property values:

1. The code creates a mutable copy `prop` from the original `prop_`
2. When a property value is simplified (e.g., `k?.x ?? {}` → `k?.x`), it
updates `prop.value`
3. **Bug:** The code then wrote back `prop_` (the original) instead of
`prop` (the modified copy)

Because `simplifyUnusedExpr` mutates the AST in place when handling
nullish coalescing (setting `bin.right` to empty), the original `prop_`
now contained an expression with `bin.right` as an empty/missing
expression, resulting in invalid output.

### How did you verify your code works?
- Added regression test in `test/regression/issue/25398.test.ts`
- Verified the original reproduction case passes
- Verified existing CommonJS tests continue to pass
- Verified test fails with system bun and passes with the fix

2025-12-07 16:33:37 -08:00

1.9 KiB

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