It seems to affect pages URLs that contain a comma character (and maybe other characters are affected?)

There's also another issue - filter_limit being applied before label filter.

Here one example from demo.piwik.org:

http://demo.piwik.org/index.php?module=API&method=Actions.getPageTitles&format=XML&idSite=7&period=day&date=2014-06-03,2014-07-02&expanded=1&label=Daylight%2520saving%2B&token_auth=anonymous&filter_limit=30

That's the default one - row evolution report export.

And here with disabled filter_limit:

http://demo.piwik.org/index.php?module=API&method=Actions.getPageTitles&format=XML&idSite=7&period=day&date=2014-06-03,2014-07-02&expanded=1&label=Daylight%2520saving%2B&token_auth=anonymous&filter_limit=-1

@ kuba.cc suggestion seems to be the actual issue see ResponseBuilder. I'm gonna try to move the label filter upwards just to see which test fail afterwards...

In df3427b: refs #5397 wondering which tests will fail when applying the label filter before limit filter & co

Tests fail after moving the label filter, see https://travis-ci.org/piwik/piwik/jobs/29283168

I think one problem is that "SafeDecodeLabel" ( https://github.com/piwik/piwik/blob/master/core/API/ResponseBuilder.php#L319 ) is no longer executed before the LabelFilter meaning the tests should be updated meaning we would change the API.

We could recommend to always use filter_limit = -1 when a label filter is used but doesn't sound very intuitive. Especially our export links in the UI would have to take care of this as well :( A hack to always set the filter_limit to -1 when a label filter is used results in even more problems in the end.

So basically to keep the API the same we'd have to "undo" the SafeDecodeLabel of the label url parameter and then compare. This could work

Couldn't really fix it without breaking anything. Maybe someone else wants to have a look?

Changing title since the bug is only present when a filter_limit is present.