Packaging multiple Typescript projects depending on the same common local module

I tried @matt-mccutchen's approach, but unfortunately, I couldn't get that to work with the VSTS build tasks due to the fact that these tasks require commonjs:

"compilerOptions": {
  "module": "commonjs",
  "target": "es6", 

But I did find a solution that works for me.

In the Tasks folder I've added a tsconfig.json which defines my default settings and includes the files from the Common library:

{
  "compileOnSave": true,
  "compilerOptions": {
    "module": "commonjs",
    "target": "es6",
    "sourceMap": true,
    "strict": false,
    "strictNullChecks": false,
    "removeComments": true
  },
  "files": [
    "./Common/uuidv5.d.ts",
    "./Common/Common.ts"
  ]
}

Then in each task I created a tsconfig.json which sets the output folder to the current folder for that project and which inherits from the tsconfig.json in the Tasks folder:

{
  "extends": "../tsconfig.json",
  "compilerOptions": {
      "outDir": "./", 
      "sourceRoot": "./"
  },
  "files": [
      "InstallExtension.ts"
  ]
}

This results in:

 - MyExtension
   - package.json // containing all dev-dependencies
   - tslint.json
   - Tasks
     - tsconfig.json   // Including Common by default
     - Common
       - common.ts     // containing functionality shared across tasks
       - package.json  // containing all runtime dependencies for Common
       - tsconfig.json // containing build configuration for just the common files, inherits from ..\Task\tsconfig.json
     - My1stTask
       - package.json  // containing all prod-dependencies for the task
       - task.ts       // containing task implementation
       - tsconfig.json // containing build configuration for the task, inherits from ..\Task\tsconfig.json
     - ...
     - ...
     - My6thTask
       - package.json // containing all prod-dependencies
       - task.ts      // containing task implementation
       - tsconfig.json // containing build configuration for the task, inherits from ..\Task\tsconfig.json

When compiling a task the following

     - My6thTask
       - Common
         - Common.js   // Compiled common
       - My6thTask
         - task.js     // Compiled task
       - package.json  // containing all prod-dependencies
       - task.ts       // containing task implementation
       - task.json     // defining the task UI
       - tsconfig.json // containing build configuration for the task

The only thing I had to add to task.ts is the following:

///<reference path="../Common/Common.ts"/>
import * as common from "../Common/Common";

And to change the execution handler in the task.json to point to the new location:

  "execution": {
    "Node": {
      "target": "InstallExtension/InstallExtension.js", // was: InstallExtension.js
      "argumentFormat": ""
    }
  }

And all seems fine :D. Combined with using glob-exec I've been able to reduce the build time to less than a minute when building clean:

"initdev:npm": "npm install & glob-exec --parallel --foreach \"Tasks/*/tsconfig.json\" -- \"cd {{file.dir}} && npm install\"",
"compile:tasks": "glob-exec \"Tasks/*/tsconfig.json\" -- \"tsc -b {{files.join(' ')}}\"",
"lint:tasks": "glob-exec --parallel --foreach \"Tasks/*/tsconfig.json\" -- \"tslint -p {{file}}\"",