'fileSystem' is only allowed for packaged apps, and this is a legacy packaged app

Question

I need to use the fileSystem permission in the manifest.js, so I can read/write files from my Chrome extension.

When I load my extension with the "Load unpacked extension" button, Chrome displays:

'fileSystem' is only allowed for packaged apps, and this is a legacy packaged app.

So for Chrome my extension is a legacy packaged app.

My question is how to technically convert a "legacy packaged app" into a "packaged apps" so I can test the fileSystem API ?

Here is my manifest:

{
 "name": "MyApp",
 "version": "1.0",
 "manifest_version": 2,
  "app": {
  "launch": {
  "local_path": "index.html"
  }
 },
 "icons": {
 "128": "favicon.ico"
 },
  "permissions" : [
    "fileSystem"
  ]
}

Indeed I'm already using "manifest_version": 2.

Answer 1

Packaged apps have a different structure in the "app" section of the manifest. Your manifest.json would be something like:

{
  "name": "MyApp",
  "version": "1.0",
  "manifest_version": 2,
  "app": {
    "background": {
      "scripts": [
        "main.js"
      ]
    }
  },
  "icons": {
    "128": "favicon.ico"
  },
  "permissions": [
    "fileSystem"
  ]
}

and you would also need a background script ("main.js" in this sample) that opens your index.html when the user clicks on the app icon:

chrome.app.runtime.onLaunched.addListener(function() {
  chrome.app.window.create('index.html', {
    bounds: {
      width: 500,
      height: 300
    }
  });
});