[Bug]: transformFromAstSync leaks memory #13970

💻

• Would you like to work on a fix?

How are you using Babel?

Programmatic API (babel.transform, babel.parse)

Input code

for (let i = 0; i < 1e7; i++) {
    ast = babel.transformFromAstSync(ast, src, {
      configFile: false,
      ast: true,
    }).ast;
  }

For a complete reproduction, see https://github.com/JLHwung/babel-transform-from-ast-leak

Configuration file name

No response

Configuration

N.A.

Current and expected behavior

Current: The memory usage rises beyond 2GB

Expected: The memory usage should be stable during repetitive transformFromAstSync calls.

Environment

System:
OS: macOS 12.0.1
Binaries:
Node: 17.0.1 - /opt/homebrew/bin/node
Yarn: 1.22.17 - /opt/homebrew/bin/yarn
npm: 8.1.0 - /opt/homebrew/bin/npm
npmPackages:
@babel/core: ^7.16.0 => 7.16.0

Possible solution

No response

Additional context

Found this issue when running jest --detect-leaks in the Babel codebase.

transformFromAstAsync and transformFromAst are also affected.

When switching transformFromAstSync to transformSync, the memory leakage can not be reproduced.