Support of Clipboard API without `--allow-run`

[rsp]

Summary

Deno could implement operations for getting and setting the system clipboard (copy/paste).

I wrote a library for Deno that does that but it needs the all-powerful --allow-run that ruins the permission system.

The browsers implement it with a standard API that could be used.

We would need new permissions like --allow-copy and --allow-paste because this would be a security risk to give access to the clipboard with no restrictions (people often copy/paste personal data, passwords, API keys and other credentials). In the browsers there are separate permissions "clipboard-read" and "clipboard-write" in the standard Permissions API.

document.execCommand

The older API to use the clipboard in the browsers was document.execCommand("copy"),
document.execCommand("cut") and document.execCommand("paste"), see:

• https://developer.mozilla.org/en-US/docs/Web/API/Document/execCommand

navigator.clipboard

The newer API to use the clipboard in the browsers is via the global navigator.clipboard object:

• https://developer.mozilla.org/en-US/docs/Web/API/Navigator/clipboard

From MDN on Clipboard:

The Clipboard API adds to the Navigator interface the read-only clipboard property, which returns the Clipboard object used to read and write the clipboard's contents. The Clipboard API can be used to implement cut, copy, and paste features within a web application.

Use of the asynchronous clipboard read and write methods requires that the user grant the web site or app permission to access the clipboard. This permission must be obtained from the Permissions API using the "clipboard-read" and/or "clipboard-write" permissions.

The clipboard object has 4 methods:

read() Requests arbitrary data (such as images) from the clipboard, returning a Promise. When the data has been retrieved, the promise is resolved with a DataTransfer object that provides the data.

readText() Requests text from the system clipboard; returns a Promise which is resolved with a DOMString containing the clipboard's text once it's available.

write() Writes arbitrary data to the system clipboard. This asynchronous operation signals that it's finished by resolving the returned Promise.

writeText() Writes text to the system clipboard, returning a Promise which is resolved once the text is fully copied into the clipboard.

deno.land/x/clipboard

I wrote a library for Deno that implements readText() and writeText() on Linux, Mac and Windows:

• https://github.com/rsp/deno-clipboard

The navigator.clipboard also implements the EventTarget interface which my library doesn't.

navigator.clipboard in Deno?

This seems like something that would be ideally exposed by Deno itself:

• so the libraries don't spawn external processes just to use the clipboard
• so that the permissions can be controlled
• so that it is maximally familiar to how the browsers work

It would be most optimal to use the standard window.navigator:

• https://developer.mozilla.org/en-US/docs/Web/API/Navigator

Or should it be exposed in some other non-standard place like Deno.clipboard?

References

• https://github.com/rsp/deno-clipboard
• Add clipboard module for copy/paste dotland#132
• https://developer.mozilla.org/en-US/docs/Web/API/Clipboard
• https://developer.mozilla.org/en-US/docs/Web/API/Clipboard_API
• https://developer.mozilla.org/en-US/docs/Web/API/Permissions_API
• https://developer.mozilla.org/en-US/docs/Web/API/Navigator/clipboard
• https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/Interact_with_the_clipboard

[timreichen]

I would be in favor of having navigator.clipboard according to the clipboard API specs.

[ry]

I'm also in favor of having navigator.clipboard. Tho we need to consider the security carefully.

[crowlKats]

after finishing localStorage, i was thinking of working on this. what about --allow-clipboard-write & --allow-clipboard-read for perms?

[nayeemrmn]

Also note that the runtime permissions API for this should be at navigator.permissions.

[crowlKats]

So a bit ago i tried working on this, but there is a major problem: there is no cross platform crate to do what we need. i am not knowledgeable enough to make one myself either, so not sure what we can do but wait for one to emerge

Still waiting for this to be implemented.
I write system commands in JavaScript and run them through deno.

One use case I have:

urldecode -clip <someurl>
which copies the URL to the clipboard instead of printing to the console.

This is currently not possible through native functions.

[aiotter]

So a bit ago i tried working on this, but there is a major problem: there is no cross platform crate to do what we need. i am not knowledgeable enough to make one myself either, so not sure what we can do but wait for one to emerge

How about this one?
https://github.com/ArturKovacs/arboard

It seems being deprecated on README, but actually it is just processing the ownership transfer now (https://github.com/ArturKovacs/arboard/issues/26).

It seems the required work for navigator.clipboard is not yet finished (see their any-format branch), but it's worth checking this repo for possibility to be used as a means of implementing the API.

[crowlKats]

We have discussed this, and we will not implement this, as it ties us to windowing systems (same reasoning as the Notification API), which we do not want as we want to keep deno headless.

[aiotter]

I'm sorry to hear that, but it's reasonable.
How about GUI interfaces (#3234)? Won't implement either?