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https://github.com/oven-sh/bun
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9c96937329
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
55 lines
1.9 KiB
TypeScript
55 lines
1.9 KiB
TypeScript
import { expect, test } from "bun:test";
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import { bunEnv, bunExe, tempDir } from "harness";
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// https://github.com/oven-sh/bun/issues/25398
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// Bug: Object spread with nullish coalescing to empty object literal
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// in unused expression statements was incorrectly simplified,
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// resulting in invalid JavaScript output like `k?.x ?? ` (missing {})
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test("object spread with nullish coalescing to empty object in arrow function body", async () => {
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// This pattern is common in Webpack-style CommonJS chunks
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using dir = tempDir("issue-25398", {
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"test.js": `exports.id=1,exports.ids=[1],exports.modules={1:(a,b,c)=>{let k={};({...k,a:k?.x??{}})}};`,
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});
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await using proc = Bun.spawn({
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cmd: [bunExe(), "run", "test.js"],
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cwd: String(dir),
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env: bunEnv,
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stdout: "pipe",
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stderr: "pipe",
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});
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const [stdout, stderr, exitCode] = await Promise.all([proc.stdout.text(), proc.stderr.text(), proc.exited]);
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// Should not throw "Expected CommonJS module to have a function wrapper"
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expect(stderr).not.toContain("Expected CommonJS module to have a function wrapper");
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expect(exitCode).toBe(0);
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});
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test("object spread with nullish coalescing preserves value in simplification", async () => {
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// This specifically tests that the value after ?? is preserved when used
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using dir = tempDir("issue-25398-preserve", {
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"test.js": `
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let result;
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const f = () => { let k = {x: null}; result = {...k, a: k?.x ?? {default: true}}; };
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f();
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console.log(JSON.stringify(result));
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`,
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});
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await using proc = Bun.spawn({
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cmd: [bunExe(), "run", "test.js"],
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cwd: String(dir),
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env: bunEnv,
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stdout: "pipe",
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stderr: "pipe",
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});
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const [stdout, stderr, exitCode] = await Promise.all([proc.stdout.text(), proc.stderr.text(), proc.exited]);
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expect(stderr).toBe("");
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expect(JSON.parse(stdout.trim())).toEqual({ x: null, a: { default: true } });
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expect(exitCode).toBe(0);
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});
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