Potential v7 breaking changes

This issue is to track potential improvements to Karma, which require breaking changes. It will be updated with more points as I discover them.

• Drop support for IE < 11 and other obsolete browsers to simplify Karma code and allow using more modern JS in the client code. I think it is reasonable to support same set as Angular does, but open for suggestions.
  • Use the Array.prototype.includes() method instead of a full-fledged for-loop in https://github.com/karma-runner/karma/blob/6b3bf3b295febc4a6b47bb284bbcae68d648ec72/client/karma.js#L242
  • Update mocha - it is currently used for cross-browser testing and hence blocked
  • Switch from socket.io to ws to simplify code and reduce amount of dependencies (WebSockets are supported in any reasonably alive browsers, so it may be a good point for a switch as we no longer need fallback mechanisms with only IE 11 supported) - may not do that given that not all proxies, e.g. BrowserStack Local support WebSockets
    • Remove buffering logic for test results (#3684)
• Remove deprecated customFileHandlers provider once ecosystem is ready
• Remove support for http2 module. It was implemented over a long deprecated https://yarnpkg.com/package/http2 package. WebSockets in general (https://github.com/websockets/ws/issues/1458) and socket.io, in particular, do not work over HTTP/2 (https://github.com/socketio/socket.io/issues/3564). Node’s http2 module is not compatible with http and https, so we’ll have to build some complex adapters. And on top of that, the current implementation does not seem to work at the moment (https://github.com/karma-runner/karma/issues/2761).
• Drop Node 10 support as it is reaching EOL (https://nodejs.org/en/about/releases/) and blocks dependency updates (https://github.com/karma-runner/karma/pull/3686)
  • Update “@commitlint/config-angular” as mentioned in https://github.com/karma-runner/karma/pull/3719#discussion_r740546736.
• Remove parseConfig() flags introduced in https://github.com/karma-runner/karma/pull/3660 and https://github.com/karma-runner/karma/pull/3635 and enable behavior by default
• Make parseConfig() resolve configFile path relative to the CWD instead of relative to the karma/lib/config.js to make programmatic API and CLI work the same (https://github.com/karma-runner/karma/issues/1636)
• Resolve relative plugin paths relative to the basePath or CWD for consistent resolution using both CLI and programmatic approaches
• Remove jsVersion configuration property support.
• Remove mkdirp dependency and use docs instead (See https://github.com/karma-runner/karma/pull/3750).
• Include https://github.com/karma-runner/karma/pull/3726.
• AI in https://github.com/karma-runner/karma/commit/d9dade2f004a340e49c9a633177576200c286404.
• Consider listening on IPv6 by default. See https://github.com/karma-runner/karma/issues/3730#issuecomment-1128501402.

[johnjbarton]

I think we should stick with the shorter list for v6, including the reconnect changes I am working on. We can then start v7 immediately focusing on the IE<11 code. Any v6 issues will be cleared up then.

[devoto13]

@XhmikosR Yes, I agree. See “Remove support for http2 module.”` checkbox in the issue.