c1584b8a35
## Summary - Fixes #20321 - spawnSync crashes with RangeError when stdio is set to process.stderr - Handles file descriptors in stdio array correctly by treating them as non-captured output ## Problem When `spawnSync` is called with `process.stderr` or `process.stdout` in the stdio array, Bun.spawnSync returns the file descriptor number (e.g., 2 for stderr) instead of a buffer or null. This causes a RangeError when the code tries to call `toString(encoding)` on the number, since `Number.prototype.toString()` expects a radix between 2 and 36, not an encoding string. This was blocking AWS CDK usage with Bun, as CDK internally uses `spawnSync` with `stdio: ['ignore', process.stderr, 'inherit']`. ## Solution Check if stdout/stderr from Bun.spawnSync are numbers (file descriptors) and treat them as null (no captured output) instead of trying to convert them to strings. This aligns with Node.js's behavior where in `lib/internal/child_process.js` (lines 1051-1055), when a stdio option is a number or has an `fd` property, it's treated as a file descriptor: ```javascript } else if (typeof stdio === 'number' || typeof stdio.fd === 'number') { ArrayPrototypePush(acc, { type: 'fd', fd: typeof stdio === 'number' ? stdio : stdio.fd, }); ``` And when stdio is a stream object (like process.stderr), Node.js extracts the fd from it (lines 1056-1067) and uses it as a file descriptor, which means the output isn't captured in the result. ## Test plan Added comprehensive regression tests in `test/regression/issue/20321.test.ts` that cover: - process.stderr as stdout - process.stdout as stderr - All process streams in stdio array - Mixed stdio options - Direct file descriptor numbers - The exact AWS CDK use case All tests pass with the fix. 🤖 Generated with [Claude Code](https://claude.ai/code) --------- Co-authored-by: Claude Bot <claude-bot@bun.sh> Co-authored-by: Claude <noreply@anthropic.com> Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
Tests
Finding tests
Tests are located in the test/ directory and are organized using the following structure:
test/js/- tests for JavaScript APIs.cli/- tests for commands, configs, and stdout.bundler/- tests for the transpiler/bundler.regression/- tests that reproduce a specific issue.harness.ts- utility functions that can be imported from any test.
The tests in test/js/ directory are further categorized by the type of API.
test/js/bun/- tests forBun-specific APIs.node/- tests for Node.js APIs.web/- tests for Web APIs, likefetch().first_party/- tests for npm packages that are built-in, likeundici.third_party/- tests for npm packages that are not built-in, but are popular, likeesbuild.
Running tests
To run a test, use Bun's built-in test command: bun test.
bun test # Run all tests
bun test js/bun # Only run tests in a directory
bun test sqlite.test.ts # Only run a specific test
If you encounter lots of errors, try running bun install, then trying again.
Writing tests
Tests are written in TypeScript (preferred) or JavaScript using Jest's describe(), test(), and expect() APIs.
import { describe, test, expect } from "bun:test";
import { gcTick } from "harness";
describe("TextEncoder", () => {
test("can encode a string", async () => {
const encoder = new TextEncoder();
const actual = encoder.encode("bun");
await gcTick();
expect(actual).toBe(new Uint8Array([0x62, 0x75, 0x6E]));
});
});
If you are fixing a bug that was reported from a GitHub issue, remember to add a test in the test/regression/ directory.
// test/regression/issue/02005.test.ts
import { it, expect } from "bun:test";
it("regex literal should work with non-latin1", () => {
const text = "这是一段要替换的文字";
expect(text.replace(new RegExp("要替换"), "")).toBe("这是一段的文字");
expect(text.replace(/要替换/, "")).toBe("这是一段的文字");
});
In the future, a bot will automatically close or re-open issues when a regression is detected or resolved.
Zig tests
These tests live in various .zig files throughout Bun's codebase, leveraging Zig's builtin test keyword.
Currently, they're not run automatically nor is there a simple way to run all of them. We will make this better soon.
TypeScript
Test files should be written in TypeScript. The types in packages/bun-types should be updated to support all new APIs. Changes to the .d.ts files in packages/bun-types will be immediately reflected in test files; no build step is necessary.
Writing a test will often require using invalid syntax, e.g. when checking for errors when an invalid input is passed to a function. TypeScript provides a number of escape hatches here.
// @ts-expect-error- This should be your first choice. It tells TypeScript that the next line should fail typechecking.// @ts-ignore- Ignore the next line entirely.// @ts-nocheck- Put this at the top of the file to disable typechecking on the entire file. Useful for autogenerated test files, or when ignoring/disabling type checks an a per-line basis is too onerous.