JDT changes the project after calling codeSelect of CompilationUnit

[andxu]

JDTUtils.findElementAtSelection will call codeSelect which will lost the original project information for JDK classes like java.lang.String, sees it is related to the SelectionEngine in JDT(eclispse has the same issue too), because of this issue, the java dependency viewer will not link the tree node for SDK classes since the default project is not displayed in tree explorer(when opening a folder containing multiple projects)

[yaohaizh]

The same bug/issue is also reproed on eclipse UI.

[fbricon]

does it need to be fixed upstream (needs a bug report) or can it be done independently in jdt.ls?

[andxu]

opened: https://bugs.eclipse.org/bugs/show_bug.cgi?id=541573

[andxu]

Since from jdt side the project is set to the first one purposely, so we need to change the project from default project since default project is not aware by users.

parent IPackageFragment and IPackageFragmentRoot are reliable, just the parent IJavaProject is not

[fbricon]

Closed with #879