Develop a NativeScript plugin

This repo is heavily based on @NathanWalker's Plugin Seed. Thanks, Nathan!

TL;DR
Long Description

TL;DR

The NativeScript plugin seed is built to be used as a starting point by NativeScript plugin developers. To bootstrap your plugin development execute the following:

git clone https://github.com/NativeScript/nativescript-plugin-seed nativescript-yourplugin where nativescript--yourplugin is the name of your plugin.
cd nativescript-yourplugin/src
npm run postclone
npm run demo.ios or npm run demo.android to run the demo.
In another command prompt/terminal npm run plugin.tscwatch to watch typescript changes in the plugin and to automatically apply them in the demo.

Long Description

What is NativeScript plugin seed?

The NativeScript plugin seed is built to be used as a starting point by NativeScript plugin developers. It expands on several things presented here. What does the seed give you out of the box?

the plugin structure with option for easy development and debugging (see Development setup section below)
a simple working plugin
a demo project working with the plugin. It is useful during development and for running tests via Travis CI
plugin tests
a guideline how to structure your plugin README file that will be published to NPM
a shell script to create your plugin package
a proper .gitignore to keep GitHub tidy
a proper .npmignore to ensure everyone is happy when you publish your plugin to NPM.

Plugin folder structure

Folder/File name	Description
demo	The plugin demo source code
demo/tests	The tests for your plugin
src	The plugin source code
src/platform/android	Plugin Android specific configuration
src/platform/ios	Plugin ios specific configuration
src/README	Your plugin README stub explaining how other developers can use your plugin in their applications. Used when you publish your plugin to NPM. On postclone step, the README in the root is replaced with this one.
src/scripts	The postclone script run when you execute `npm run postclone`. Feel free to delete it after you have executed the postclone step from the Getting started section
publish	Contains a shell script to create and publish your package. Read more on creating a package and publishing in the Publish to NPM section

Getting started

Open a command prompt/terminal and execute git clone https://github.com/NativeScript/nativescript-plugin-seed nativescript-yourplugin to clone the plugin seed repository into the nativescript-yourplugin folder where nativescript--yourplugin is the name of your plugin..
Open a command prompt/terminal and navigate to nativescript-yourplugin/src folder using cd nativescript-yourplugin/src
Execute npm run postclone to:
- configure your github username - it will be changed in the package.json for you
- configure your plugin name - all files and classes in the seed will be renamed for you
- stub your plugin README.md file
- create a new repository for your plugin
- npm link your plugin the demo app - this will install the plugin dependencies and will add a symbolic link to the plugin code in the demo project allowing you to do changes and review them in the demo without adding/removing the plugin every time you make a change. Read more about npm link. If you encounter an "EACCES" permission denied error, please fix you global npm permissions, which is perfectly explained here.

Now you can continue with the development of your plugin by using the Development setup described below.

Development setup

For easier development and debugging purposes continue with the following steps:

Open a command prompt/terminal, navigate to src folder and run npm run demo.ios or npm run demo.android to run the demo.
Open another command prompt/terminal, navigate to src folder and run npm run plugin.tscwatch to watch for file changes in your plugin.

Now go and make a change to your plugin. It will be automatically applied to the demo project.

NOTE: If you need to use a native library in your plugin or do some changes in Info.plist/AndroidManifest.xml, these cannot be applied to the demo project only by npm link. In such scenario, you need to use tns plugin add ../src from the demo so that the native libraries and changes in the above-mentioned files are applied in the demo. Then you can link again the code of your plugin in the demo by using npm run plugin.link from the src.

Linking to CocoaPod or Android Arsenal plugins

You will want to create these folders and files in the src folder in order to use native APIs:

platforms --
  ios --
    Podfile
  android --
    include.gradle

Doing so will open up those native apis to your plugin :)

Take a look at these existing plugins for how that can be done very simply:

Clean plugin and demo files

Sometimes you may need to wipe away the node_modules and demo/platforms folders to reinstall them fresh.

Run npm run clean to wipe those clean then you can can run npm i to install fresh dependencies.

Sometimes you just need to wipe out the demo's platforms directory only:

Run npm run demo.reset to delete the demo's platforms directory only.

Sometimes you may need to ensure plugin files are updated in the demo:

Run npm run plugin.prepare will do a fresh build of the plugin then remove itself from the demo and add it back for assurance.

Unittesting

The plugin seed automatically adds Jasmine-based unittest support to your plugin. Open demo/app/tests/tests.js and adjust its contents so the tests become meaningful in the context of your plugin and its features.

You can read more about this topic here.

Once you're ready to test your plugin's API go to src folder and execute one of these commands:

npm run test.ios
npm run test.android

Publish to NPM

When you have everything ready to publish:

Bump the version number in src/package.json
Go to publish and execute publish.sh (run chmod +x *.sh if the file isn't executable)

If you just want to create a package, go to publish folder and execute pack.sh. The package will be created in publish/package folder.

NOTE: To run bash script on Windows you can install GIT SCM and use Git Bash.

TravisCI

The plugin structure comes with a fully functional .travis.yml file that deploys the testing app on Android emulator and iOS simulator and as a subsequent step runs the tests from UnitTesting section. All you have to do, after cloning the repo and implementing your plugin and tests, is to sign up at https://travis-ci.org/. Then enable your plugin's repo on "https://travis-ci.org/profile/<your github user>" and that's it. Next time a PR is opened or change is committed to a branch TravisCI will trigger a build testing the code.

To properly show current build status you will have to edit the badge at the start of the README.md file so it matches your repo, user and branch.

Referring tns-core-modules in the Plugin

We recommend to use full imports of tns-core-modules due to an issue in Angular CLI. Read more detailed explanation in this discussion.

Ultimately after the issue in Angular CLI is fixed this would not be a restriction, but till then the recommended approach is to import from tns-core-modules using full path. Here is an example:

WRONG

tsconfig.json

...

"paths": {
  "*": [
    "./node_modules/*",
    "./node_modules/tns-core-modules/*"
  ]
}
...

yourplugin.common.ts

import * as app from 'application';

RIGHT