Endless loop when computing symbols for toolchain header file

[jld01]

Steps to reproduce under PDE using latest cdt-lsp sources from HEAD of main branch:

1. Create a trivial CMake Core Build hello world project
2. Build the project
3. In the Project Explorer view, expand the resource tree under the generated application binary file to view the symbols in one of the toolchain header files (external to the workspace)
4. Observe the "Computing symbols..." message in the tree:
   
5. Observe high CPU load and an endless stream of messages logged:

!ENTRY org.eclipse.cdt.lsp 4 0 2025-02-27 17:20:03.654
!MESSAGE Cannot fetch elements of translation unit file:/C:/msys64/ucrt64/include/c++/14.2.0/bits/alloc_traits.h

Other information:

$ C:/msys64/ucrt64/bin/clangd  --version
clangd version 19.1.7
Features: windows
Platform: x86_64-w64-windows-gnu

[jonahgraham]

Confirmed on my Linux machine too. I didn't look as to why it tries repeatedly after initially failing. The error message comes from

cdt-lsp/bundles/org.eclipse.cdt.lsp/src/org/eclipse/cdt/lsp/internal/ui/navigator/SymbolsManager.java

Lines 215 to 219 in c23789c

	if (unit.getFile() != null) {
	compileUnit = getCompileUnit(unit.getFile().getLocationURI(), unit.getFile());
	} else {
	Platform.getLog(getClass()).error("Cannot fetch elements of translation unit " + unit.getElementName()); //$NON-NLS-1$
	}

[jonahgraham]

PS Collapsing the node does stop the background processing AFAICT.

[jld01]

The method org.eclipse.cdt.lsp.internal.ui.navigator.SymbolsManager.getCompileUnitElements(Object) needs enhancing to support ExternalTranslationUnit objects. These objects have a location URI but no IFile.