I've got a problem working on a source tree with about 10000 source files. Because for some projects only part of the tree is needed, I've divided it into several projects (so the projects are "views" on the source tree). The source files I need to update in these projects belong only to one of these, while others (needed only for building the project) may or may not be shared by multiple projects.

What's important here:
The files I need to edit and search in the projects are uniquely related to exactly one project. This is done by excluding the other files in the source tree from the project's sources.

While this all generally works well, there's a problem with finding the projects.

If I open two or more "view" projects (for working on different tasks), then searching the source in its project often results in nothing found, because a project is accidentally used, where the source is excluded.

Another problem is, the wrong project is assigned and so most needed classes are masked by Excludes, which result in error badges, though the correct project contains the needed sources.

This problem remains even after closing the "wrong" project, only restart of NB after clothing all projects with the exception of one solves the problems.

Seems, the source root is first detected, then the first project containing this root is assigned - which is often erreounous. If multiple projects are using this source root, an additional test is necessary, if the edited file isn't excluded.

I've noticed this line in org.netbeans.api.java.project.classpath.ProjectClassPathModifier:

final Project project = FileOwnerQuery.getOwner(projectArtifact);

So it's probably not java-specific.