bug: indentify the bug with XMLDocument comparison

[volodya-lombrozo]

I have faced with the problem of XMLDocument comparison. If there are two similar documents, but with different formatting, they aren't equal to each other. For example:

<program>
  <indentation/>
</program>

and

<program>
    <indentation/>
</program>

aren't equal XMLDocuments.

In this PR I added:

1. The unit test that reveals the problem with XMLDocument comparison
2. The integration test that uses XMLDocument in a Groovy script (the place where I originally have found the bug).

[volodya-lombrozo]

@yegor256 Could you take a look, please?

[yegor256]

@volodya-lombrozo well, technically, these are two different documents. In XML, spaces are not ignored - they are part of the syntax. The following document:

<a> <b/>  </a>

Is parsed into:

Element("a", [Text(" "), Element("b", []), Text("  ")])`

I'm not sure jcabi-xml should ignore all spaces (which are Text elements and may be important).

[volodya-lombrozo]

@yegor256 , what if we add one more document type, XmlDocumentTrimmed? There is definitely a request from the community:

• https://stackoverflow.com/q/13727876/10423604
• https://stackoverflow.com/q/141993/10423604
• https://stackoverflow.com/q/12351512/10423604

Moreover, I've faced with the same problem myself. I want to compare two XMLs indecently on their formatting.

[volodya-lombrozo]

@yegor256 what do you think?

[yegor256]

@volodya-lombrozo I tried to reproduce the bug in 818f3ea, but failed. Can you suggest a unit test that will show the problem?

[volodya-lombrozo]

@yegor256 Yes, you are right. My unit test doesn't reproduce the error. However, the integration test does. You can run it using the following command:

mvn clean integration-test invoker:run -Dinvoker.test=groovy -DskipTests

Does this test causes error in your environment?

[volodya-lombrozo]

@yegor256 I tried to mimic the same code in Java:

final File first = Paths.get("/absolute-path-to/first.xmir").toFile();
final File same = Paths.get("/absolute-path-to/same.xmir").toFile();
MatcherAssert.assertThat(
     new XMLDocument(first),
     Matchers.equalTo(new XMLDocument(same))
);

And it passes successfully. Most probably, this problem is groovy - specific.

[volodya-lombrozo]

@yegor256, I have finally identified the problem. In the unit tests, we use net.sf.saxon.jaxp.IdentityTransformer to convert XMLDocument into a String. In the integration tests, we use com.sun.org.apache.xalan.internal.xsltc.trax.TransformerFactoryImpl to convert XMLDocument into a String. XMLDocument uses strings to compare itself with another XMLDocument.

I have demonstrated this case in the unit test. Could you please take a look one more time?

[volodya-lombrozo]

@yegor256 What do you think?

[yegor256]

@rultor merge

[rultor]

@rultor merge

@yegor256 OK, I'll try to merge now. You can check the progress of the merge here

[rultor]

@rultor merge

@yegor256 Done! FYI, the full log is here (took me 12min)