1286744 - [XHR2] GetAllResponseHeaders() should return an empty string if the XHR failed.

Status: RESOLVED FIXED

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

Description

[Thomas Wisniewski]

The XHR spec states that GetAllResponseHeaders() should return the empty string on errors (we're in a "network error" response state, and those are stated to not have any headers). Chrome already passes the relevant web platform test:

http://w3c-test.org/XMLHttpRequest/xmlhttprequest-network-error.htm

Comment 1

[Thomas Wisniewski]

Attachment: 1286744-return_empty_string_for_getAllResponseHeaders_if_errors.diff

Here's a patch which passes the test.

Try run: https://treeherder.mozilla.org/#/jobs?repo=try&revision=dfbd3de4a26d

Comment 2

[Olli Pettay [:smaug][[e-mail]]]

Comment on attachment 8770984 [details] [diff] [review]
1286744-return_empty_string_for_getAllResponseHeaders_if_errors.diff

Where does the spec actually say that. fetch is so unreadable spec that finding anything there is rather hard.

Comment 3

[Olli Pettay [:smaug][[e-mail]]]

Ah, this "A network error is a response whose status is always 0, status message is always the empty byte sequence, header list is always empty, body is always null, and cache state is always "none". "

Comment 4

[Thomas Wisniewski]

Thanks, I'll try to be extra-clear with my wording next time to spare the extra reading exercise.

Requesting checkin.

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/54af298e7b99
Return the empty string from GetAllResponseHeaders() if the XHR failed. r=smaug

Comment 6

[Carsten Book [:Tomcat]]

https://hg.mozilla.org/mozilla-central/rev/54af298e7b99

Comment 7

[Kohei Yoshino]

Posted the site compatibility doc: https://www.fxsitecompat.com/en-CA/docs/2016/network-error-for-async-xhr-now-fires-error-event-instead-of-throwing-getallresponseheaders-will-be-empty/

Comment 8

[Jean-Yves Perrier [:teoli]]

I have precised the return value of 
https://developer.mozilla.org/en-US/docs/Web/API/XMLHttpRequest/getAllResponseHeaders
and a mention in
https://developer.mozilla.org/en-US/Firefox/Releases/50#DOM_and_HTML_DOM