fix(nix): propagate nlohmann_json, and stop pointing at a deleted file

Two small follow-ups to the shared-runtime migration.

PROPAGATE nlohmann_json. This repo re-exports the Qt host runtime headers, and
two of them -- logos_provider_object.h and logos_qt_arg_decode.h -- include
<nlohmann/json.hpp>. Anything compiling against these includes therefore needs
nlohmann on its include path whether or not it has ever heard of nlohmann.

Consumers going through find_package(logos-qt-host) already get it: that package
find_dependency's logos-protocol, which PUBLIC-links nlohmann_json. Consumers
taking the include directory directly do not, and they exist.

Set in TWO places, which is not redundant: symlinkJoin builds a NEW derivation
and does not carry the propagation of the paths it joins. Consumers take the
join, not the headers output, so setting it only on the latter reaches nobody --
measured, a consumer still failed until the join carried it too.

WHAT THIS DOES NOT FIX, measured rather than assumed: a consumer that takes
liblogos as a bare attribute and interpolates ''${logosLiblogos}/include has no
dependency edge for propagation to travel along, so it still needs nlohmann in
its own buildInputs. logos-module-viewer is that shape.

DANGLING POINTER. The comment in src/CMakeLists.txt sent readers to
logos-basecamp/cmake/LogosSharedFromDll.cmake, deleted in logos-basecamp#348 and
logos-logoscore-cli#98. Now says where it went and why.

nix build .#default PASS.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

flake.nix

@@ -192,15 +192,31 @@
           includePortable = import ./nix/include.nix { inherit pkgs src logosSdk; inherit logosProtocolPkg logosQtSdk logosQtHost; common = commonPortable; };
 
           # Combined package (dev)
+          #
+          # propagatedBuildInputs is set HERE as well as on the headers output,
+          # and that is not redundant: symlinkJoin builds a NEW derivation and
+          # does not carry the propagation of the paths it joins. Consumers take
+          # this join, not the headers output, so setting it only there reaches
+          # nobody -- measured, logos-module-viewer still failed with
+          #     fatal error: nlohmann/json.hpp: No such file or directory
+          # until it was set on the join too.
+          #
+          # nlohmann is needed because this output re-exports the Qt host runtime
+          # headers, two of which (logos_provider_object.h, logos_qt_arg_decode.h)
+          # include <nlohmann/json.hpp>. Consumers going through
+          # find_package(logos-qt-host) get it transitively; consumers taking the
+          # include directory directly do not.
           liblogos = pkgs.symlinkJoin {
             name = "logos-liblogos";
             paths = [ bin lib include ];
+            propagatedBuildInputs = [ pkgs.nlohmann_json ];
           };
 
           # Combined package (portable)
           liblogosPortable = pkgs.symlinkJoin {
             name = "logos-liblogos-portable";
             paths = [ binPortable libPortable includePortable ];
+            propagatedBuildInputs = [ pkgs.nlohmann_json ];
           };
         in
         {

nix/include.nix

@@ -8,6 +8,24 @@ pkgs.stdenv.mkDerivation {
   
   inherit src;
   inherit (common) meta;
+
+  # This output RE-EXPORTS the Qt host runtime headers, and two of them --
+  # logos_provider_object.h and logos_qt_arg_decode.h -- include
+  # <nlohmann/json.hpp>. So anything compiling against these includes needs
+  # nlohmann on its include path, whether or not it has ever heard of nlohmann.
+  #
+  # Consumers that go through find_package(logos-qt-host) already get it: that
+  # package find_dependency's logos-protocol, which PUBLIC-links nlohmann_json.
+  # Consumers that take the include directory DIRECTLY -- logos-module-viewer
+  # uses find_library + raw -I, and it is not alone in that -- bypass CMake's
+  # propagation entirely and fail with
+  #
+  #     fatal error: nlohmann/json.hpp: No such file or directory
+  #
+  # in a repo that never mentions nlohmann. Propagating it here fixes both
+  # shapes at the source rather than adding a dependency to each consumer that
+  # trips over it, which is a list that only grows.
+  propagatedBuildInputs = [ pkgs.nlohmann_json ];
   
   # No build phase needed, just install headers
   dontBuild = true;

src/CMakeLists.txt

@@ -239,7 +239,9 @@ target_compile_definitions(logos_core PRIVATE LOGOS_CORE_LIBRARY)
 # WHAT DID NOT CHANGE is the invariant. The runtime must still exist exactly
 # once per process; it is now enforced by there being one shared library per
 # type rather than by one image absorbing everything. Consumers still empty
-# their static archives (logos-basecamp/cmake/LogosSharedFromDll.cmake) so ld
+# their static archives (that was logos-basecamp/cmake/LogosSharedFromDll.cmake,
+# deleted in logos-basecamp#348 and logos-logoscore-cli#98 once they linked the
+# shared libraries directly and had no second static copy left to suppress) so ld
 # cannot pull an archive member that would redefine an imported symbol, and
 # logos-basecamp/nix/symbol-gate.nix still asserts the result.
 #