LSP4E does not seem to support multiple editors for the same file, and multiple projects for the same file

The issue exhibited here only happens when the eclipse workspace contains a file accessible from more than one project which is a common case when working on maven multi modules projects (i think gradle multi modules projects are also impacted but i did not check)

Eclipse workspace with 2 projects : parent_project, nested_project
Where nested_project is contained in parent_project

parent_project
|
-- nested_project
    |
    -- file.ext

nested_project
|
-- file.ext   

With this kind of workspace, we have two cases:

• When the projects presentation is "Hierarchical", the file edited is the most nested and the method LSPEclipseUtils.findResourceFor(uri) will return the correct IResource (provided the function LSPEclipseUtils.findMostNested works properly)
• When the projects presentation is "Flat", the method is totaly unreliable because more than one valid value can be returned and the most nested is not necessarily the one edited or the only one edited. (the test LSPEclipseUtilsTest.testURIToResourceMappingWithNestedProject provided in pull request #259 to see the issue)

So when using the "Flat" project presentation the side effects can affect the following methods:

Do you agree with my assumptions ?

Start with LSPEclipseUtils.findResourceFor(uri) and LSPEclipseUtils.findMostNested, then run LSPEclipseUtilsTest.testURIToResourceMappingWithNestedProject from pull request #259 against a workspace containing nested projects. Trace the affected methods shown in the issue and determine how flat project presentation should select the edited resource; done when the mapping is reliable and the regression test passes.