areSimilar() function support in Java8+

[JuanMorenoDeveloper]

Hi Guys

BTW Thank you for this project, It's very good and time saver.

I was using it for testing and I was an issue with the areSimilar() function when I use in Java 11+ (In Java 8 works great).

I isolated the sample code here https://github.com/earth001/jaxp-example. I configure a Travis pipeline where you can find the logs https://travis-ci.org/earth001/jaxp-example/builds/556292262 (Only pass in Java 8).

This is the log (It looks like a problem with newlines):

[INFO] Running com.proitc.JaxpProcessorUnitTest
[ERROR] Tests run: 2, Failures: 1, Errors: 0, Skipped: 0, Time elapsed: 0.602 s <<< FAILURE! - in com.proitc.JaxpProcessorUnitTest
[ERROR] givenTwoXml_whenModifyAttribute_thenGetSimilarXml  Time elapsed: 0.13 s  <<< FAILURE!
java.lang.AssertionError: 
Expecting:
 <<notification id="5">
        
    <to customer="false">jhon@email.com</to>
        
    <from>mary@email.com</from>
    
</notification>>
to be equal to:
 <<notification id="5">
    <to customer="false">jhon@email.com</to>
    <from>mary@email.com</from>
</notification>>
but was not.
	at com.proitc.JaxpProcessorUnitTest.givenTwoXml_whenModifyAttribute_thenGetSimilarXml(JaxpProcessorUnitTest.java:54)
[INFO] 
[INFO] Results:
[INFO] 
[ERROR] Failures: 
[ERROR]   JaxpProcessorUnitTest.givenTwoXml_whenModifyAttribute_thenGetSimilarXml:54 
Expecting:
 <<notification id="5">
        
    <to customer="false">jhon@email.com</to>
        
    <from>mary@email.com</from>
    
</notification>>
to be equal to:
 <<notification id="5">
    <to customer="false">jhon@email.com</to>
    <from>mary@email.com</from>
</notification>>
but was not.

Have you experienced something like this before?

Please let me know if this info is enough or if I could bring something additional.

[JuanMorenoDeveloper]

I'm not sure but it could be related to https://bugs.openjdk.java.net/browse/JDK-8215543

[bodewig]

Yes, it looks quite a bit like the test failure I've fixed with 23336de - it seems to affect any version of Java post Java8.

Back then I didn't find the time to investigate the root cause. but the issue you link is a likely candidate (DefaultComparisonFormatter uses XSLT for an "identity transformation" from DOM to String).

[JuanMorenoDeveloper]

Here http://java9.wtf/xml-transformer/ I found more info about the issue.

[bodewig]

Interesting.

Unfortunately it only confirms the behavior has changed but I still don't see what XMLUnit could do to make Java9+ behave the way we'd want it to.

[JuanMorenoDeveloper]

Yes, It's true. In order to use the similar() function, I processed the transformer output with a regex to delete the extra lines, like replaceAll("(?m)^[ \t]*\r?\n", "")

In StackOverflow mentions a similar workaround for the CDATA tags, related to another bug with the JDK (It solved in JDK 14). https://stackoverflow.com/questions/55853220/handling-change-in-newlines-by-xml-transformation-for-cdata-from-java-8-to-java
https://bugs.java.com/bugdatabase/view_bug.do?bug_id=JDK-8223291

[bodewig]

It may be a good idea to collect issues like this in the Wiki. Do you think you could add a blurb on some new kind of "know issues" page or something like that?

[JuanMorenoDeveloper]

Sure, I like the idea.

[JuanMorenoDeveloper]

I create here https://github.com/xmlunit/xmlunit/wiki/XMLUnit-with-Java-9-and-above. I hope it helps

[bodewig]

Many thanks!

When I said "the wiki" I meant the "user guide", sorry for not being clear about it. I've copied your page to https://github.com/xmlunit/user-guide/wiki/XMLUnit-with-Java-9-and-above