## Summary
Implements the `typeof undefined === 'u'` minification optimization from
esbuild in Bun's minifier, and fixes dead code elimination (DCE) for
typeof comparisons with string literals.
### Part 1: Minification Optimization
This optimization transforms:
- `typeof x === "undefined"` → `typeof x > "u"`
- `typeof x !== "undefined"` → `typeof x < "u"`
- `typeof x == "undefined"` → `typeof x > "u"`
- `typeof x != "undefined"` → `typeof x < "u"`
Also handles flipped operands (`"undefined" === typeof x`).
### Part 2: DCE Fix for Typeof Comparisons
Fixed dead code elimination to properly handle typeof comparisons with
strings (e.g., `typeof x <= 'u'`). These patterns can now be correctly
eliminated when they reference unbound identifiers that would throw
ReferenceErrors.
## Before/After
### Minification
Before:
```javascript
console.log(typeof x === "undefined");
```
After:
```javascript
console.log(typeof x > "u");
```
### Dead Code Elimination
Before (incorrectly kept):
```javascript
var REMOVE_1 = typeof x <= 'u' ? x : null;
```
After (correctly eliminated):
```javascript
// removed
```
## Implementation
### Minification
- Added `tryOptimizeTypeofUndefined` function in
`src/ast/visitBinaryExpression.zig`
- Handles all 4 equality operators and both operand orders
- Only optimizes when both sides match the expected pattern (typeof
expression + "undefined" string)
- Replaces "undefined" with "u" and changes operators to `>` (for
equality) or `<` (for inequality)
### DCE Improvements
- Extended `isSideEffectFreeUnboundIdentifierRef` in `src/ast/P.zig` to
handle comparison operators (`<`, `>`, `<=`, `>=`)
- Added comparison operators to `simplifyUnusedExpr` in
`src/ast/SideEffects.zig`
- Now correctly identifies when typeof comparisons guard against
undefined references
## Test Plan
✅ Added comprehensive test in `test/bundler/bundler_minify.test.ts` that
verifies:
- All 8 variations work correctly (4 operators × 2 operand orders)
- Cases that shouldn't be optimized are left unchanged
- Matches esbuild's behavior exactly using inline snapshots
✅ DCE test `dce/DCETypeOfCompareStringGuardCondition` now passes:
- Correctly eliminates dead code with typeof comparison patterns
- Maintains compatibility with esbuild's DCE behavior
🤖 Generated with [Claude Code](https://claude.ai/code)
Co-Authored-By: Claude <noreply@anthropic.com>
---------
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>
Co-authored-by: Jarred Sumner <jarred@jarredsumner.com>
Co-authored-by: Dylan Conway <dylan.conway567@gmail.com>
in JS, `new TextDecoder("latin1").decode(...)` uses cp1252. In python,
latin1 is half-width utf-16. In our code, latin1 typically refers to
half-width utf-16 because JavaScriptCore uses that for most strings, but
sometimes it refers to cp1252. Rename the cp1252 functions to be called
cp1252
Also fixes an issue where Buffer.from with utf-16le would sometimes
output the wrong value:
```js
$> bun -p "Buffer.from('\x80', 'utf-16le')"
<Buffer ac 20>
$> node -p "Buffer.from('\x80', 'utf-16le')"
<Buffer 80 00>
$> bun-debug -p "Buffer.from('\x80', 'utf-16le')"
<Buffer 80 00>
```
Replace `catch bun.outOfMemory()`, which can accidentally catch
non-OOM-related errors, with either `bun.handleOom` or a manual `catch
|err| switch (err)`.
(For internal tracking: fixes STAB-1070)
---------
Co-authored-by: Dylan Conway <dylan.conway567@gmail.com>
### What does this PR do?
This PR adds builtin YAML parsing with `Bun.YAML.parse`
```js
import { YAML } from "bun";
const items = YAML.parse("- item1");
console.log(items); // [ "item1" ]
```
Also YAML imports work just like JSON and TOML imports
```js
import pkg from "./package.yaml"
console.log({ pkg }); // { pkg: { name: "pkg", version: "1.1.1" } }
```
### How did you verify your code works?
Added some tests for YAML imports and parsed values.
---------
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>
Co-authored-by: Jarred Sumner <jarred@jarredsumner.com>
* `IncrementalGraph(.client).File` packs its fields in a specific way to
save space, but it makes the struct hard to use and error-prone (e.g.,
untagged unions with tags stored in a separate `flags` struct). This PR
changes `File` to have a human-readable layout, but adds methods to
convert it to and from `File.Packed`, a packed version with the same
space efficiency as before.
* Reduce the need to pass the dev allocator to functions (e.g.,
`deinit`) by storing it as a struct field via the new `DevAllocator`
type. This type has no overhead in release builds, or when
`AllocationScope` is disabled.
* Use owned pointers in `PackedMap`.
* Use `bun.ptr.Shared` for `PackedMap` instead of the old
`bun.ptr.RefPtr`.
* Add `bun.ptr.ScopedOwned`, which is like `bun.ptr.Owned`, but can
store an `AllocationScope`. No overhead in release builds or when
`AllocationScope` is disabled.
* Reduce redundant allocators in `BundleV2`.
* Add owned pointer conversions to `MutableString`.
* Make `AllocationScope` behave like a pointer, so it can be moved
without invalidating allocations. This eliminates the need for
self-references.
* Change memory cost algorithm so it doesn't rely on “dedupe bits”.
These bits used to take advantage of padding but there is now no padding
in `PackedMap`.
* Replace `VoidFieldTypes` with `useAllFields`; this eliminates the need
for `voidFieldTypesDiscardHelper`.
(For internal tracking: fixes STAB-1035, STAB-1036, STAB-1037,
STAB-1038, STAB-1039, STAB-1040, STAB-1041, STAB-1042, STAB-1043,
STAB-1044, STAB-1045)
---------
Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
Co-authored-by: Jarred Sumner <jarred@jarredsumner.com>
Co-authored-by: Claude Bot <claude-bot@bun.sh>
Co-authored-by: Claude <noreply@anthropic.com>
