1604308 - Figure out what the right behaviour is for a forced download and a 404.

Status: NEW

(Core :: DOM: Core & HTML, task)

Description

[Matt Woodrow (:mattwoodrow)]

Attachment: download-404.py

We can have a download forced (either by a 'download' attribute on a link, or the Content-Disposition header), and still get a 404 response.

The current behaviour, here, is that we return NS_ERROR_FILE_NOT_FOUND from nsDocumentOpenInfo, and then the docshell displays a 'file not found' neterror page.

Bug 1574372 is changing behaviour so that the content process takes this path, returns NS_ERROR_WONT_HANDLE_CONTENT, and is handled silently.

html/semantics/text-level-semantics/the-a-element/a-download-click-404.html is a web-platform-test that requires the silent no-load behaviour, at least for the link attribute variation. We previously failed this, and will now pass after bug 1574372.

Other browser behaviour (for top-level loads and the Content-Disposition header, testing script attached):

• Chrome - Displays a net error page
• Safari - Displays the 404 content
• Edge - Displays a net error page

Comment 1

[Boris Zbarsky [:bzbarsky]]

Hmm. So in the other browsers @download is not equivalent to a server-sent Content-Disposition header, right?

Comment 2

[Matt Woodrow (:mattwoodrow)]

Attachment: links.html

That's correct.

Added a second part of the testcase that shows behaviour of various links:

Edge:

• Download attribute + 404 (regardless of Content-Disposition) - Couldn't download dialog at bottom
• Normal 404 link - Loads 404 content page
• 404 link + Content-Disposition:attachment - Silently ignored.

Chrome:

• Download attribute + 404 (regardless of Content-Disposition) - Couldn't download dialog at bottom
• Normal 404 link - Loads 404 content page
• 404 link + Content-Disposition:attachment - Loads net error page.

Firefox (right now):

• Download attribute + 404 (regardless of Content-Disposition) - Loads net error page.
• Normal 404 link - Loads 404 content page
• 404 link + Content-Disposition:attachment - Loads net error page.

Firefox (post-bug 1574372)

• Download attribute + 404 (regardless of Content-Disposition) - Silent.
• Normal 404 link - Loads 404 content page
• 404 link + Content-Disposition:attachment - Silent.

Comment 4

[Marco Bonardo [:mak]]

Matt, based on Bug 1744220 other browsers like Edge and Chrome are indeed showing a download error when there's a download attribute.
This is marked as a Task but we may actually consider it a defect, based on users expectations.
Do we have a plan for it?

Comment 5

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

Clear a needinfo that is pending on an inactive user.

Inactive users most likely will not respond; if the missing information is essential and cannot be collected another way, the bug maybe should be closed as INCOMPLETE.

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