1293761 - contentScriptWhen not working properly in e10s

Status: RESOLVED WONTFIX

(Add-on SDK Graveyard :: General, defect, P3)

Description

[Siavash]

I created a small script with the issue:
https://gist.github.com/CIAvash/6a95931b4d43abeb7ae5d05719ed335f

I show the problem with an example, when I open a png image in non-e10s window contentType is "image/png"

but when I open it in an e10s window, contentType is "text/html"(and url of the tab is about:blank), when I refresh the page, contentType shows "image/png". Also it correctly shows "image/png" when I change contentScriptWhen to "end".

from #addons IRC channel:
<John-Galt> I'm guessing the problem is that we replace the first about:blank
            document with the image document after the about:blank document
            has partially loaded. And then the SDK code ignores it, because it
            checks whether it's seen that document already.

Comment 1

[:shell escalante]

triage in Monday meeting

Comment 2

[:shell escalante]

luca is looking at alternatives in webextensinos on content scripts and will write up ideas/ new bugs

Comment 3

[Luca Greco [:rpl] [:luca] [:lgreco]]

Follows a workaround, that use the same Addon SDK PageMod API used in the example linked in the Comment 0 but with a slightly different approach, which works on both non-e10s and e10s modes:

    const { PageMod } = require('sdk/page-mod');
    let pm = PageMod({
      include: /.*/,
      contentScriptWhen: 'start',
      contentScript: `
        self.port.emit("attachedDocumentInfo", {
          contentType: document.contentType,
          url: document.documentURI,
        });
      `,
      onAttach: function onAttach(worker) {
        worker.port.on("attachedDocumentInfo", (args) => {
          const {contentType, url} = args;
          console.log(`Attached document "${url}"`, 
                      `with contentType "${contentType}"`);
        });
      }
    });

The above code snippet simply sends the document contentType from the content script code (where the value of `document.contentType` is directly accessible and always updated) to the Addon SDK code running in the main process (instead of using tab.contentType, which is actually retrieved from a value that is cached in the main process).

Comment 4

[:shell escalante]

does the work-around work for you in comment 3?  Looking at fixing the core issue of timing is likely to break other items - so if work around can fix it - that would best.

Comment 5

[Siavash]

Yes, the workaround works. Thanks :)

Comment 6

[:shell escalante]

sounds great Siavash - going to close as won't fix - since there's a work-around and any fix is likely to break other timing