1764677 - FormData.entries() iterator is not iterable in extension content script

Status: NEW

(WebExtensions :: Untriaged, defect, P3)

Description

[kevin.zun]

Steps to reproduce:

Created an extension with this content script:

let f = new FormData();
f.append('foo', 'bar');
try {
    console.log([...f.entries()]);
} catch (err) {
    console.error(err);
}

Actual results:

I got a type error

TypeError: f.entries() is not iterable
    <anonymous> moz-extension://1a7245f5-d90c-43b2-b806-bd9e6536d54d/content.js:4

Expected results:

Log [['foo', 'bar']] to the console, no error.

Comment 1

[BugBot [:suhaib / :marco/ :calixte]]

The Bugbug bot thinks this bug should belong to the 'WebExtensions::Untriaged' component, and is moving the bug to that component. Please correct in case you think the bot is wrong.

Comment 2

[Alex Cornestean]

Hello,

I reproduced the issue on the latest Nightly (101.0a1/20220417212536), Beta (100.0b7/20220417185951) and Release (99.0.1/20220411174855) under Windows 10 x64 and Ubuntu 16.04 LTS.

After loading the extension via about:debugging, accessing a page declared in the manifest.json file for the content script match, logged the error from comment 0 in the console.

For further details, see the attached screenshot.

Comment 3

[Alex Cornestean]

Attachment: 2022-04-18_10h33_35.png

Comment 4

[BugBot [:suhaib / :marco/ :calixte]]

The severity field is not set for this bug.
:mixedpuppy, could you have a look please?

For more information, please visit auto_nag documentation.

Comment 5

[Rob Wu [:robwu]]

This specific error happens because the Symbol.iterator property is apparently hidden when an object is wrapped by a XrayWrapper.

Run the following from a content script to see the difference:

{
  let entries = new FormData().entries();
  console.log(entries[Symbol.iterator]);
    // = undefined
  console.log(entries.wrappedJSObject[Symbol.iterator]);
    // = function Symbol.iterator()
}

FormData is an iterable according to FormData.webidl, so I would expect any generated standard methods to be defined.

I looked up a random other iterator, new Headers().entries()[Symbol.iterator] and was initially surprised that it did expose an iterator,
and then I recalled that it's because the content script sandbox includes its own Headers definition (the "fetch" export in the content script sandbox triggers the inclusion of Headers in Sandbox.cpp).

Comment 6

[Tom S [:evilpie]]

This is basically a dupe of bug 1023984.