1381031 - downloadItem.exists does not change from true to false when a file is removed

Status: NEW

(WebExtensions :: General, defect, P5)

Description

[Rob Wu [:robwu]]

Attachment: dowloads-exists.zip

STR:
1. Download attached extension.
2. Visit about:debugging, load extension.
3. Click on extension button.
4. Open the global console (or inspect the devtools of the extension's background page).

Expected:
- The extension downloads a file from example.com, waits until the download finishes and removes the file. Then it queries the DownloadItem information, and shows whether the API claims that the file exists.
- The console should show (the following expectation is from Chrome 59):
downloads.download callback with ID: 1
Download finished, going to remove downloaded file with ID 1
downloads.onChanged delta.exists = Object {current: false, previous: true}
downloads.removeFile done undefined
PASS: Downloaded file exists=false


Actual (Firefox Developer edition v55.0b8, but same behavior is also seen in Firefox Nightly):
downloads.download callback with ID: 1
downloads.onChanged delta.exists = Object { previous: false, current: true }
Download finished, going to remove downloaded file with ID 1
downloads.removeFile done null
FAIL: Downloaded file exists=true

Notes:
- The relevant part of the test is after the "Download finished, going to remove" message.
- Firefox fires downloads.onChanged with a delta for "exists" from "false" to "true" when the download is created. Chrome does not. Either behavior is acceptable and NOT THE SUBJECT OF THIS BUG REPORT.
- Firefox does NOT fire the downloads.onChanged event when the file is removed.
- When downloads.search is used, the returned DownloadItem always has exists=true, even when the actual file has been removed.

Comment 1

[Oleksandr]

My few cents about: downloads.DownloadItem - does not update the "exists" property
--------------
A boolean indicating whether a downloaded file still exists (true) or not (false). This information might be out-of-date, as browsers do not automatically watch for file removal — to check whether a file exists, call the downloads.search() method, filtering for the file in question.
https://developer.mozilla.org/en-US/Add-ons/WebExtensions/API/downloads/DownloadItem

--------------
1. download file
2. remove file from system
3. call "chrome.downloads.search" or "chrome.downloads.open"
4. DownloadItem.exists = true!