facebookarchive/prepack

Prepack emits code containing invalid global.TypedArray access

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#2,292 opened on Jul 18, 2018

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Description

TypedArray is a global not exposed to the user JavaScript runtime. Try global.TypedArray in your JavaScript environment of choice. We must emit Object.getPrototypeOf(Int8Array) or similar instead of TypedArray.

Input

var TypedArray = Object.getPrototypeOf(Int8Array);
console.log(TypedArray.from.name === "from");

Output

var TypedArray;
(function() {
  var _$0 = this;

  var _$1 = _$0.TypedArray; // <-------------------- `TypedArray` is not exposed on the global object!
  _$0.TypedArray = _$1;
  console.log(true);
}.call(this));

Contributor guide

Research direction
Inspect how Prepack's resolver handles global property accesses like `global.TypedArray` and how it resolves `Object.getPrototypeOf(Int8Array)`. Trace the code path that leads to emitting the invalid `TypedArray` access.
Tech stack
javascript
Domain
build systemdeveloper experience
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
JavaScriptPrototypes
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
60