Support Platform Specific Extensions

[windyGex]

I can't find answer from stack overflow, so I open a issue.

[auchenberg]

In your extension activation callback, you are free to check and download extensions as soon as the extension get's activated. This is how Live Share is downloading their dependencies after installation

export async function activate(context: vscode.ExtensionContext) {
  /// 1 Check if deps are installed
 await downloadDependencies()
 // Update status bar or output channel to give an indicator of status
}

[windyGex]

If install dependencies when extension activate, I think it' too later and it maybe cost a long time.

[sandy081]

Idea is to provide a post install hook similar to uninstall hook. This will be executed after an extension is installed or updated.

"scripts": {
    "vscode:prepublish": "tsc -p ./",
	"vscode:install": "node ./out/src/extensionInstall"
    "vscode:uninstall": "node ./out/src/extensionUninstall"
},

An extension can install necessary libraries and stuff using this post install script. An unique location per extension is provided through an env variable for the extension to maintain any state. The same location will also be passed with post uninstall script.

[DonJayamanne]

Idea is to provide a post install hook similar to uninstall hook. This will be executed after an extension is installed or updated.

I would prefer a better name. Today vscode:prepublish applies to developer of the extension, i.e. to extension authors. Having vscode: install would indicate it's related to extension authors again and not in end user machines.