[507077] Do not emit empty concatenation

[rovarga]

Java code generated from Xtend routinely contains output
like:

public CharSequence packageDefinition() {
StringConcatenation _builder = new StringConcatenation();
_builder.append("package ");
String _packageName = this.type.getPackageName();
_builder.append(_packageName, "");
_builder.append(";");
return _builder;
}

While StringConcatenation will detect the fact the indentation
string is empty, it is at the cost of runtime performance.

Before emitting the call to StringConcatenation, check if our
literal would end up being an empty string and if it would,
call the no-indentation append() variant instead.

Signed-off-by: Robert Varga nite@hq.sk

[eclipsewebmaster]

Issue tracker reference:
https://bugs.eclipse.org/bugs/show_bug.cgi?id=507077

[svenefftinge]

Have you executed the tests? I would assume that some test expectations would need to be updated for this, too.

[rovarga]

Unfortunately I was unable to do so -- gradle built only part of the project and maven build failed on what I assume is wrong settings.xml. Can you point me at a howto?

[spoenemann]

You can see in Jenkinsfile what Maven arguments are used by the server to build and test.

I pushed your branch to this repo so the tests are run automatically:
http://services.typefox.io/open-source/jenkins/job/xtext-xtend/job/rovarga_emptyIndent/

[spoenemann]

The commit needs to be rebased onto master so the build works properly.

Here are the test results:
http://services.typefox.io/open-source/jenkins/job/xtext-xtend/job/rovarga_emptyIndent/lastCompletedBuild/testReport/

[rovarga]

@spoenemann Thanks, I have rebased the patch for now. That Jenkinsfile helped, I am running the tests now and will post a fixed up version later today,

[rovarga]

Should be ready to go, as far as I can tell (later tests seem to have massive memory requirements, hence failed on OOM for me).

[spoenemann]

Thanks!