Message passing: can't pass file handle or other objects that aren't JSON-serializable

[NV]

Currently, it isn't possible to pass the file handler object using browser.runtime.sendMessage, yet it works fine with window.postMessage.

• browser.runtime.sendMessage requires the message to be JSON-serializable.
• postMessage serializes data using the structured clone algorithm, which allows passing many Web API objects.

I propose to make message-passing object serialization logic work the same as for postMessage.

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In my particular case, I want an extension to back up data to a file periodically. Currently, I have to use IndexedDB to pass the file handler to the service worker. (There are more hurdles to overcome before I could write to a file periodically, but those are out of the scope of this proposal.)

[tophf]

It's already summarized by Rob--W in #293 (comment).

P.S. For chrome-extension:// scripts (i.e. not content scripts) there's a faster workaround: serviceWorker messaging (the example calls register() but you won't need to).

[NV]

Good to know. I'll close it then.

Thanks for the workaround!