This will create all deliverables from the NativeScript repo in the bin/dist/*.tgz folder:

npm install
grunt

This will register the location of the tns-core-modules sources as symlink in your npm:

cd tns-core-modules
npm link

To rebuild the JavaScript of the tns-core-modules, in the root of the NativeScript repo:

# this will update tns-core-modules.d.ts references with new .d.ts files
grunt generate-tns-core-modules-dev-dts
# this will rebuild the TS to JS
tsc

Then you can navigate to any NativeScript App and add the tns-core-modules from the NativeScript repo to the node_modules/tns-core-modules in the app with:

npm link tns-core-modules

You should be able to debug the App in VSCode, breakpoints in the node_modules/tns-core-modules TypeScript files should work. Changes in the App's node_modules/tns-core-modules will edit the files in the NativeScript repo so you should be able to easily add changes to git.

There is tests folder with regular NativeScript application that runs tests on the tns-core-modules. To run them (see Using tns-core-modules from source in app):

npm install
grunt generate-tns-core-modules-dev-dts
tsc

cd tns-core-modules
npm link
cd ..

cd tests
npm link tns-core-modules
cd ..

tns run [ios|android] --path tests

You can rapidly apply canges to the tns-core-modules and tests, and to run the tests, at the root of the NativeScript repo, execute:

# optionally, if you have added new .d.ts files
grunt generate-tns-core-modules-dev-dts

tsc
tns run [ios|android] --path tests