Multiple small changes

[kduske-n4]

Sorry to submit multiple changes in one pull request (and not using branches), but I had to make these changes in quick succession and could not isolate them. They are independent of each other, however. There are three changes:

Convert nested Java maps to Ruby hashes in RubyHashUtil#toRubyObject
This prevents a ClassCastException when, after creating a new block in a block processor, you attempt to access the attributes of that block later in a tree processor. When asking the block for its attributes, AsciidoctorJ assumes that what it gets from the asciidoctor AST is an instance of RubyHash, when in this case what it really gets is an instance of MapJavaProxy that was injected by JRuby into the asciidoctor AST when the block was created originally.

I'm not sure about this change, since I had to choose one of several different methods to convert Java maps to Ruby hashes in RubyHashUtil.

Return null if the inner document of a table cell is nil
This prevents a NullPointerException when attempting to access the inner document of a table cell in a processor when that cell doesn't have an inner document in the asciidoctor AST.

Add getter for @content_model
This adds a getter for the @content_model attribute of an asciidoctor AbstractBlock to StructuralNode.

I hope these changes are useful for you and that you can apply them. I have run the tests in the asciidoctorj-asciidoctorj and asciidoctorj-distribution projects and there were no failures.

[robertpanzer]

I haven't tested it, but I don't think this will compile.

[kduske-n4]

It does, though. Why shouldn't it?

[robertpanzer]

Gotcha! :-)
Could you please add braces around the return null?

I probably automatically put them in there mentally around both returns that have the same indentation.

[kduske-n4]

Done.

[robertpanzer]

Thanks a lot for your great contribution, Kristian!

Would you mind adding tests for the three problems you fixed?
That should be

• a test that simply invokes getContentModel (Maybe like here:

  asciidoctorj/asciidoctorj-core/src/test/java/org/asciidoctor/WhenAsciiDocIsRenderedToDocument.java

  Line 149 in 07fed40

  Document document = asciidoctor.load(ROLE, new HashMap<String, Object>());

  )
• a test that uses two extensions, where one creates a node and another that tries to access the attributes? (Maybe copy this test and accommodate to the needs:

  asciidoctorj/asciidoctorj-core/src/test/groovy/org/asciidoctor/extension/WhenABlockMacroProcessorCreatesATable.groovy

  Line 51 in 07fed40

  def "the table should be rendered to html"() {

  )
• A test that tries to access the inner document of a table cell when it doesn't have the Asciidoctor style. That should fit in here: https://github.com/asciidoctor/asciidoctorj/blob/asciidoctorj-1.6.0/asciidoctorj-core/src/test/groovy/org/asciidoctor/WhenATableIsLoaded.groovy

That would help us a lot and would avoid that we later stumble over these problems again.

[kduske-n4]

Added test cases as requested.

[robertpanzer]

Thanks a lot! Such tests really help us.
Executed them locally and they look good, if I revert the main code, I can also see the errors that you fixed.

There are a couple of code style problems that codenarc complains.
Would you mind fixing them?
While it might seem pedantic it helps us to keep a common code style across the groovy code.
When doing a ./gradlew clean build codenarc will create a report that shows you what it doesn't like.

Thanks a lot!

Cheers
Robert

[kduske-n4]

Sure, will do!

[kduske-n4]

Done ;-)

[kduske-n4]

Some things still seem broken in your CI. I have run the tests locally and it was fine. Any hints?

[robertpanzer]

Yes, there are some problems with Asciidoctor PDF and JRuby on Windows.
That's why this test is in. :-)
Will upgrade the JRuby version soon and look if it works better now (even though I don't have much hope)
Unix build is green, so I'm fine to merge.

Thanks!