**Steps to replicate the issue** (include links if applicable):
* Create a repo with a package.json file, a package-lock.json file, and a JS script file
* Add a "heroku-build" script inside, that executes the JS script
* In the JS script, import `{env}` from the "node:process" module, and print the environment variables : `console.error(JSON.stringify(env));` for instance ([[ https://codeberg.org/Gouvernathor/ParliamentDiagram-Toolforge-deployer/src/commit/76cd49202846ad5e5045049e4cb7a26b07bf0a9a/build.ts | example file ]] with some other stuff in it)
**What happens?**:
TOOL_DATA_DIR is not among the environment variables.
**What should have happened instead?**:
As it says [[ https://wikitech.wikimedia.org/wiki/Help:Toolforge/Envvars | here ]], under "Globally set environment variables", that variable should exist, and contain a path whose last component is the name of the tool.
**Other information** (browser name/version, screenshots, etc.):
Tested on the parliamentdiagram-beta tool.