Upgrading from Gulp 3 to Gulp 4 in Ionic project

Due to the WKWebView change I’ve need to upgrade certain dependencies in my Ionic project, which in turn lead to other dependencies needing to be upgraded.
The latest upgrade is moving from Gulp 3 to 4 which leads to the following error;

throw err;

AssertionError [ERR_ASSERTION]: Task function must be specified
at Gulp.set [as _setTask] (/Users/ucdsbdev/Mobile.iOS/UCDSB.Mobile/node_modules/undertaker/lib/set-task.js:10:3)
at Gulp.task (/Users/ucdsbdev/Mobile.iOS/UCDSB.Mobile/node_modules/undertaker/lib/task.js:13:8)
at Object. (/Users/ucdsbdev/Mobile.iOS/UCDSB.Mobile/gulp/build.js:9:6)
at Module._compile (internal/modules/cjs/loader.js:1138:30)
at Object.Module._extensions…js (internal/modules/cjs/loader.js:1158:10)
at Module.load (internal/modules/cjs/loader.js:986:32)
at Function.Module._load (internal/modules/cjs/loader.js:879:14)
at Module.require (internal/modules/cjs/loader.js:1026:19)
at require (internal/modules/cjs/helpers.js:72:18)
at requireDir (/Users/ucdsbdev/Mobile.iOS/UCDSB.Mobile/node_modules/require-dir/index.js:123:33) {
generatedMessage: false,
actual: false,
expected: true,
operator: ‘==’

Does anyone have experience moving from Gulp 3 to 4 and/or can you identify which file(s) in the above statement actually needs the code to be upgraded?

You really should take this time to ugprade to the latest v5 releases. These include better tooling and so many bug fixes .