Edge: browserAction.setIcon not working when using a default icon with multiple sizes

Question

I can't get browser.browserAction.setIcon to work in Microsoft Edge when manifest.json is specifying a default icon in multiple sizes:

manifest.json

{
  "manifest_version": 2,
  "name": "test",
  "version": "0.0.1",
  "author": "John Doe",
  "background": {
    "scripts": ["background.js"],
    "persistent": false
  },
  "browser_action": {
    "default_icon": {
      "19": "icon.png",
      "38": "icon2.png"
    }
  }
}

background.js

setInterval(function() {
  browser.browserAction.setIcon({
      path: "testimage.png"
  });
}, 2000);

No error logged, the code is executed but the icon doesn't change. The same code works fine in Chrome.

Changing the manifest.json to

"browser_action": {
  "default_icon": "icon.png"
}

Fixes the issue, but what if I need to use multiple default icons?

EDIT:

Unfortunately not even "default_icon": "icon.png" is usable, even though Edge happily loads the extension, when submitting it to the store, the validation fails with

Validation failed: Invalid type: string (expected object) Schema location: /properties/browser_action/allOf/0/properties/default_icon/type Manifest location: /browser_action/default_icon Validation failed for extension manifest: Extension\manifest.json

Which is indeed what MDN says: https://developer.mozilla.org/en-US/Add-ons/WebExtensions/manifest.json/browser_action#Browser_compatibility

'default_icon' must be an object, with explicit sizes.

Answer 1

In the end I came to the conclusion that Edge doesn't like string values for the browser action icon path, neither in manifest.json nor in browserAction.setIcon, it fails silently without producing any error.

A way to make it work is to always set explicit sizes in both manifest.json and in every browserAction.setIcon call, even if the different sizes all point to the same image.

manifest.json

{
  "manifest_version": 2,
  "name": "test",
  "version": "0.0.1",
  "author": "John Doe",
  "background": {
    "scripts": ["background.js"],
    "persistent": false
  },
  "browser_action": {
    "default_icon": {
      "19": "icon.png",
      "38": "icon2.png"
    }
  }
}

background.js

browser.browserAction.setIcon({
    path: {
      "19": "testimage.png",
      "38": "testimage.png"
});