Description of the change

This PR replaces the abandoned istanbul-instrumenter-loader with coverage-istanbul-loader.

Both are webpack loaders that use istanbul to instrument js files with istanbul-lib-instrument.

This fixes npm install which was failing with this error:

❯ npm install
npm ERR! code ERESOLVE
npm ERR! ERESOLVE could not resolve
npm ERR!
npm ERR! While resolving: [email protected]
npm ERR! Found: [email protected]
npm ERR! node_modules/webpack
npm ERR!   dev webpack@"^5.88.2" from the root project
npm ERR!   peer webpack@">=2" from [email protected]
npm ERR!   node_modules/babel-loader
npm ERR!     dev babel-loader@"^8.0.4" from the root project
npm ERR!   4 more (eslint-loader, grunt-webpack, karma-webpack, terser-webpack-plugin)
npm ERR!
npm ERR! Could not resolve dependency:
npm ERR! peer webpack@"^2.0.0 || ^3.0.0 || ^4.0.0" from [email protected]
npm ERR! node_modules/istanbul-instrumenter-loader
npm ERR!   dev istanbul-instrumenter-loader@"^3.0.1" from the root project
npm ERR!
npm ERR! Conflicting peer dependency: [email protected]
npm ERR! node_modules/webpack
npm ERR!   peer webpack@"^2.0.0 || ^3.0.0 || ^4.0.0" from [email protected]
npm ERR!   node_modules/istanbul-instrumenter-loader
npm ERR!     dev istanbul-instrumenter-loader@"^3.0.1" from the root project

Background

istanbul-instrumenter-loader is incompatible with webpack versions above 4.x, and since it's been abandoned, it lacks support for webpack 5.x.

Other options considered

babel-plugin-istanbul was considered as a modern alternative but since it works at a Babel-level and is not a webpack loader, it was dropped in favor of a webpack-loader solution to keep changes to a minimum ensuring same behavior.

Note on insertions/deletions

Main changes are 2 lines, the rest is package-lock.json.

Type of change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Maintenance
• New release

Checklists

Development

• Lint rules pass locally
• The code changed/added as part of this pull request has been covered with tests
• All tests related to the changed code pass in development

Code review

• This pull request has a descriptive title and information useful to a reviewer. There may be a screenshot or screencast attached
• "Ready for review" label attached to the PR and reviewers assigned
• Issue from task tracker has a link to this pull request
• Changes have been reviewed by at least one other engineer