Just make a build script and then write a flatpak build file that’ll package it as a flatpak. Here’s an example.

I’ve worked it out, thanks for the responses, maybe I didn’t word the question properly or something, but here’s what I did for anyone interested in the future:

You only need to do this once for every machine you want to work on.

Add the llvm freedesktop sdk extensions to get a clangd executable to your flatpak manifest:

"sdk-extensions": [
        "org.freedesktop.Sdk.Extension.llvm18"
    ],

Install these extensions:

• Native Debug
• Flatpak
• Meson Build
• clangd (optional)

Run the Flatpak: Build command in the command palette (Ctrl+Shift+P) this might take a minute. Make sure you have the required sdks installed (see the manifest for details).

There should now be two folders: .flatpak and _build. There should also be a script generated at .flatpak/meson.sh. Run:

python gen-flatpak-scripts.py

This will generate .flatpak/gdb.sh and .flatpak/clangd.sh. If you want to use the clangd vscode extension extension add this to .vscode/settings.json:

"clangd.path": "./.flatpak/clangd.sh"

Now run the clangd: Restart language server command in the command palette (Ctrl+Shift+P) and you should be good to go!

gen-flatpak-scripts.py:

# Simple script to generate scripts to make life easy when using flatpak with vscode

import subprocess;

def gen_script(outfile, exec):
    with open(".flatpak/meson.sh", "rt") as fin:
        with open(outfile, "wt") as fout:
            for line in fin:
                fout.write(line.replace("/usr/bin/meson", exec))
    subprocess.run(["chmod", "+x", outfile])

# GDB for debugging
gen_script(".flatpak/gdb.sh", "/usr/bin/gdb")
# clangd for suggestions
gen_script(".flatpak/clangd.sh", "/usr/lib/sdk/llvm18/bin/clangd")

I’m not sure I understand what you’re asking. It seems like you’re asking why your clangd extension isn’t working? But then you say:

BTW I’m not talking about using clangd with the vscode flatpak package