Feed Syndication no longer working in J! 3.6.x

[dautrich]

Steps to reproduce the issue and ### Actual result

Since I updated to J! 3.6.0, the module Syndication Feeds does no longer work correctly.
Can be seen on www.neudorf-mkk.de under navigation item "Aktuelle Informationen" (s. Syndication_1.jpg). This menu item is a category blog for category "Aktuelle Informationen".
I added a module of type "Syndication Feeds" in the left sidebar further down the page (s. Syndication_2.jpg, watch the link in the browser status line).
Opening this link (s. Syndication_3.jpg and Syndication_4.jpg), we end up on the same page as before.

Expected result

The link produced by the Syndication Feeds module should represent an XML file in format RSS 2.0.
The expected result showed up till J! 3.5.x.

System information (as much as possible)

See systeminfo-2016-08-21T13_03_05+02_00.txt

[dautrich]

Sorry, forgot the attachmentssysteminfo-2016-08-21T13_03_05+02_00.txt

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[brianteeman]

1. CAn you please switch to one of the default templates (protostar or beez) and see if you still have the problem
2. Can you disable sef in global configuration and see if you still have the problem

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[dautrich]

I disabled SEF in global configuration. The problem disappears!
screen shot 2016-08-21 at 06 29 36

I cannot easily switch to a default template, because I deleted them. But the issue seems to be related to SEF.

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[brianteeman]

It could also be your template.

[dautrich]

I don't believe that the issue is related to my template (Contryside3R from A4Joomla). With this template, the feed syndication worked fine until J! 3.5.x.

But I will try with Protostar.

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[dautrich]

Protostar shows exactly the same behaviour as Countryside3R: Issue with SEF=on, no issue with SEF=off.

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[brianteeman]

I cant replicate this problem on a clean install of joomla where the syndicate link is NOT the same as you have
?format=feed&type=rss

testing that on your site works correctly.

Do you have a third party sef extension installed

[dautrich]

There are a lot of extensions installed, but I don't think there is a SEF related one.

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[dautrich]

Works fine with SEF=on:
http://www.neudorf-mkk.de/aktuelle-informationen.feed?format=feed&type=rss

Works fine with SEF=off:
http://www.neudorf-mkk.de/index.php?option=com_content&view=category&layout=blog&id=24&Itemid=478&format=feed&type=rss

When SEF=on, the following link is generated:
http://www.neudorf-mkk.de/aktuelle-informationen.feed?type=rss
This doesn't work. Obviously, the parameter "format=feed" is missing.

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[dautrich]

Until July 15, 2016, the feed syndication worked fine.
Since then, I installed two new extensions und updated Joomla core and a number of extensions. Here is my installation and update activity log:

July 15, 2016:

• Advanced Module Manager 6.1.4FREE
• Joomla 3.6.0
• German Language Package 3.6.0.1

July 21, 2016:

• Advanced Module Manager 6.1.5FREE
• jEvents 3.4.14

July 28, 2016:

• jEvents 3.4.16
• JooAg Shariff 3.2.11 (new extension)

August 1-4, 2016

• Akeeba Backup 5.1.3
• JCE 2.5.20
• Add to Menu 5.0.3FREE
• Advanced Module Manager 6.2.0FREE
• Joomla! Update Component Update 3.6.1
• Joomla 3.6.1

August 5, 2016

• Akeeba Backup 5.1.4
• Joomla 3.6.2

August 6-9, 2016

• Add to Menu 5.0.4FREE
• jEvents 3.4.17
• German Language Package 3.6.2.1
• SimpleFacebookMeta 1.1 (new extension)

August 5, 2016

• JCE 2.5.24
• OSMap 4.1.4
• Advanced Module Manager 6.2.2FREE

Do you think that one of the extensions causes the issue?

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[mbabker]

This doesn't work. Obviously, the parameter "format=feed" is missing.

If you're using file suffixes in your SEF config (looks like you are), you shouldn't need to explicitly declare the format as it should be inferred from the .feed suffix before the query string starts.

[ggppdk]

Yes it must be the issue:
#7459

If you have any 3rd party plugin or core joomla plugin code that calls any method inside onAfterInitialise event that leads to JDocument creation,

will breaks URLs created via parameter "Add suffix to URL" by creating wrong JDocument type

[dautrich]

How can I find out whether I have a plugin like this installed?

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[ggppdk]

1. Edit this file (go to this line in your website): https://github.com/joomla/joomla-cms/blob/staging/libraries/joomla/document/html.php#L113
2. Open in your browser, the feeds URL, that is shown wrongly as HTML in your site
3. Add temporarily:

echo "<pre>"; debug_print_backtrace(DEBUG_BACKTRACE_IGNORE_ARGS); echo "</pre>";

1. Refresh the page and you will get a printed trace that will show which code makes this effect
2. Go back to the file that you edited , undo and save to make it as it was before
3. Go to page with the printed trace and you will probably find /plugins/system/ somewhere in it