How does Project Explorer finds the root project

[jdneo]

Apologies if this is a basic question, but I’m curious—

Given a set of IProjects imported from a multi-module project, how does the Project Explorer determine which one is the root project? Does it rely on the path structure or something else?

[mickaelistria]

Does it rely on the path structure

Yes, it does.

[jdneo]

So it iterates over the path of the projects and find the shortest common path, is it correct?

[mickaelistria]

Yes. see the various bits of logic in https://github.com/eclipse-platform/eclipse.platform.ui/tree/master/bundles/org.eclipse.ui.navigator.resources/src/org/eclipse/ui/internal/navigator/resources/nested .
Trying to imagine the reason why you're asking, here is an interesting thing to note: the code here uses the Common Navigator Framework, and those bits (filters, providers...) are declared as extensions to the CNF and easily reusable by any CommonViewer; so if you're trying to build a similar tree, a good approach can be to make you tree be a CommonViewer and attach in plugin.xml the various extensions/bits of behavior you'd like it to include.

[jdneo]

Thank you @mickaelistria.

Trying to imagine the reason why you're asking

In github copilot, user can put .github/copilot-instructions.md file at the project root as a part of the prompt. details

So I'm finding some official way to find the roots.

BTW, maybe a little bit off-topic:

In lsp4e, it will threat every IProject as a workspace folder: https://github.com/eclipse-lsp4e/lsp4e/blob/main/org.eclipse.lsp4e/src/org/eclipse/lsp4e/LSPEclipseUtils.java#L1311

I was trying to understand why it's not the root project as workspace folder.

[mickaelistria]

I was trying to understand why it's not the root project as workspace folder.

There is no such thing as a root project in the Eclipse workspace model; projects are independent enough, it's just that some include some others. The root project is a presentation thing only.
And even in general, a random complex polyglot multi-modular project, there is hardly a root: each subfolder could be a distinct root opened and managed separately, even with different language servers playing parts in it.

[jdneo]

Ok, I think I can just directly search for that relative path for each IProject, which is simple and straightforward.

[merks]

I think what your looking for is the root of the git repository, i.e., the root of the clone that contains the project and you are assuming the project comes from a git repo which these days is probably typically the case but not actually generally the case.

You should definitely not assume that the root of a repository will necessarily also be a IProject in the workspace.

Here is rather an ugly hacky solution we implemented in Oomph for such a purpose (find repository root of an IProject) which also supports SVN (via horrible reflection):

https://github.com/eclipse-oomph/oomph/blob/0179847a8a8460487312c3ca83ec3f144cf2d5ce/plugins/org.eclipse.oomph.predicates/src/org/eclipse/oomph/predicates/impl/RepositoryPredicateImpl.java#L251

I'm not saying this is beautiful or ideal, but I think it's solving the same general problem as you are trying to solve...