PrettyPrinter adds empty attribute with xmlns

[ashawley]

An element with an xmlns attribute gets converted to a string correctly, but using the pretty printer to convert the XML to a string adds an extra, empty attribute. I have no insight on how to fix the pretty printer.

There is a failing unit test provided by this pull request that can reproduce this issue:

[error] Test scala.xml.XMLTest.issue28 failed: expected:<...x:foo xmlns:x="gaga"[]/>> but was:<...x:foo xmlns:x="gaga"[ xmlns=""]/>>
:9:19: '/' expected instead of ''                  ^
:9:19: name expected, but char '' cannot start a name                  ^

[adriaanm]

Thanks for the test case! Even better than a bug report :-) I hope a fix will come forth! (I don't have any insights here either, unfortunately.)

[ashawley]

@adriaanm Looks like it might be an improper use of null as a default argument. Should it be TopScope instead? I'm not familiar with the code base to know for sure, nor whether other references to null in the formatter should be fixed as well.

[adriaanm]

We're about to find out thanks to Travis :-)

[adriaanm]

Cool! Could you ping one of the other recent PR submitters to get a second opinion? I really have no clue about namespacing in xml.

[ashawley]

@bartschuller, Any interest in reviewing a fix for the defect where the PrettyPrinter makes an empty namespace attribute? @adriaanm wants a second opinion

<x:foo xmlns:x="bar" xmlns="" />

[bartschuller]

I agree, In XML with namespaces you sometimes need to invent xmlns attributes, but this is not such a case. Expected behavior here is that what you put in is what you get out.

[adriaanm]

Thank you both! Very happy to see such quick turnaround (sorry I was the blocking factor here -- happy to take myself out of the loop if someone would like to step up and manage pull requests).