`expose-gc` not working after upgrading from mocha 8.x to mocha 9.1.2

Prerequisites

test.js with:

console.log(global.gc)

Description

After upgrading from mocha 8.x to mocha 9.1.2 the old --expose-gc option (or expose-gc config item) is not functional anymore.

It seems that at some point along the way that option got renamed to --gc-global. However the Node.js option is still called --expose-gc. Passing --gc-global to mocha results in Node.js being launched with --gc-global which has no effect.

Steps to Reproduce

mocha --expose-gc ./test.js   # absolutely no effect, this option is not recognized anymore
mocha --gc-global ./test.js     # launches node with --gc-global which has no effect either

Expected behavior:

node --expose-gc node_modules/mocha/lib/cli/cli.js  ./test.js # functional

Versions

mocha 9.1.2 node 14.18.2 Ubuntu 20.04 ts-node 9.1.1

[juergba]

Does mocha -n expose-gc work? Does mocha --v8-expose-gc work?

Node accepts both --gc_global and --gc-global, at least with my Node v16.12.0.

[Patrik-Stas]

I have run into this just now as well. I was running mocha like this

TS_NODE_PROJECT=./test/tsconfig.json NODE_ENV=test RUST_BACKTRACE=full ./node_modules/.bin/mocha --timeout 10000 --expose-gc --recursive --use_strict --require ts-node/register ./mytest.test.ts

and global.gc is undefined on mocha 9.1.x but I found the latest version it works at is mocha 9.0.3