Change:
<ins> { stdenv , lib , fetchFromGitHub , cmake , ninja , python , withGodef ? true , godef , withGotools ? true , gotools , withTypescript ? true , typescript , abseil-cpp , boost , llvmPackages , fixDarwinDylibNames , Cocoa }: stdenv.mkDerivation { pname = "ycmd"; version = "unstable-2023-11-06"; disabled = !python.isPy3k; # required for third_party directory creation src = fetchFromGitHub { owner = "ycm-core"; repo = "ycmd"; rev = "0607eed2bc211f88f82657b7781f4fe66579855b"; hash = "sha256-SzEcMQ4lX7NL2/g9tuhA6CaZ8pX/DGs7Fla/gr+RcOU="; fetchSubmodules = true; }; nativeBuildInputs = [ cmake ninja ] ++ lib.optional stdenv.hostPlatform.isDarwin fixDarwinDylibNames; buildInputs = with python.pkgs; with llvmPackages; [ abseil-cpp boost libllvm.all libclang.all ] ++ [ jedi jedi-language-server pybind11 ] ++ lib.optional stdenv.isDarwin Cocoa; buildPhase = '' export EXTRA_CMAKE_ARGS="-DPATH_TO_LLVM_ROOT=${llvmPackages.libllvm} -DUSE_SYSTEM_ABSEIL=true" ${python.pythonOnBuildForHost.interpreter} build.py --system-libclang --clang-completer --ninja ''; dontConfigure = true; # remove the tests # # make __main__.py executable and add shebang # # copy over third-party libs # note: if we switch to using our packaged libs, we'll need to symlink them # into the same spots, as YouCompleteMe (the vim plugin) expects those paths # to be available # # symlink completion backends where ycmd expects them installPhase = '' rm -rf ycmd/tests find third_party -type d -name "test" -exec rm -rf {} + chmod +x ycmd/__main__.py sed -i "1i #!${python.interpreter} " ycmd/__main__.py mkdir -p $out/lib/ycmd cp -r ycmd/ CORE_VERSION *.so* *.dylib* $out/lib/ycmd/ mkdir -p $out/bin ln -s $out/lib/ycmd/ycmd/__main__.py $out/bin/ycmd # Copy everything: the structure of third_party has been known to change. # When linking our own libraries below, do so with '-f' # to clobber anything we may have copied here. mkdir -p $out/lib/ycmd/third_party cp -r third_party/* $out/lib/ycmd/third_party/ '' + lib.optionalString withGodef '' TARGET=$out/lib/ycmd/third_party/godef mkdir -p $TARGET ln -sf ${godef}/bin/godef $TARGET '' + lib.optionalString withGotools '' TARGET=$out/lib/ycmd/third_party/go/src/golang.org/x/tools/cmd/gopls mkdir -p $TARGET ln -sf ${gotools}/bin/gopls $TARGET '' + lib.optionalString withTypescript '' TARGET=$out/lib/ycmd/third_party/tsserver ln -sf ${typescript} $TARGET ''; # fixup the argv[0] and replace __file__ with the corresponding path so # python won't be thrown off by argv[0] postFixup = '' substituteInPlace $out/lib/ycmd/ycmd/__main__.py  --replace __file__ "'$out/lib/ycmd/ycmd/__main__.py'" ''; meta = with lib; { description = "A code-completion and comprehension server"; mainProgram = "ycmd"; homepage = "https://github.com/ycm-core/ycmd"; license = licenses.gpl3; maintainers = with maintainers; [ rasendubi lnl7 siriobalmelli ]; platforms = platforms.all; }; } </ins>

Discussion:
Steps to reproduce the behavior: Running in a development shell yields a better error message: I will submit a PR to fix this myself. Will do on the PR. Please run and paste the result. Add a :+1: [reaction] to [issues you find important]. [reaction]: [issues you find important]: