[no-empty-group] [no-empty-capturing-group] detect inplace manipulation of arrays

[danielrentz]

Description

The rules [no-empty-group] and [no-empty-capturing-group] trigger when the group has been filled from a joined array that has been filled dynamically using push.

const arr = [];
arr.push("a", "b"); // simplified; original code processes some other data
const rex = new RegExp("(" + arr.join("|") + ")");

This (simplified) example triggers because the rules seem to see only the initialization to an empty array. The rule could be improved by detecting inplace manipulations with push, unshift etc.

[ota-meshi]

Thank you for posting this issue!

After investigating the cause, I found that it was a problem with a library we was using, so I made a PR to eslint-utils.

eslint-community/eslint-utils#257