Ninja not working with CMake

[ghost]

Reproduce

$ mkdir build
$ cd build
$ cmake -GNinja ..
$ nina
ninja: error: 'src/rhea-prefix/lib/librhea-s.a', needed by 'output/libAqtCassowaryPlugin.so', missing and no known rule to make it

Default GNU make generator works fine though.

[ghost]

@ske-ableton do you have an idea of why this might be? I guess it's because the way we include third party dependencies?

[ske-ableton]

Yes, building rhea in the aqt-cassowary build is a hack. It should be a superbuild instead, so that rhea is built with externalproject, and then aqt-cassowary is built as an external project.

Is the bundling of rhea temporary?

Here's an extension of the hack for making it work with Ninja:

diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 429c7ba..8e19ae8 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -46,7 +46,10 @@ else()
     set(rhea_lib_location "${CMAKE_CURRENT_BINARY_DIR}/rhea-prefix/lib/librhea-s.a")
   endif()
   set_property(TARGET Rhea::Rhea PROPERTY IMPORTED_LOCATION "${rhea_lib_location}")
-  add_dependencies(Rhea::Rhea RheaBuild)
+  add_custom_command(OUTPUT "${rhea_lib_location}"
+    COMMAND ${CMAKE_COMMAND} -E echo
+    COMMENT "")
+  add_custom_target(RheaHack SOURCES "${rhea_lib_location}")
+  add_dependencies(Rhea::Rhea RheaBuild RheaHack)
   set(Rhea_INCLUDE_DIR "${CMAKE_CURRENT_BINARY_DIR}/rhea-prefix/include")
 endif()
 if(WIN32)

[ghost]

What is a superbuild? I think submoduling Rhea is desirable because it's a moving target and it's a small dependency anyways. What would be a solution that allows submoduling it but not relying on hacks? My knowledge of CMake is not big enough to distinguish a hack from a non-hack though 😄

[ske-ableton]

Currently the CMakeLists for the top-level of aqt-cassowary uses externalproject to build rhea and then builds aqt-cassowary directly.

Superbuild would mean that the top level CMakeLists of aqt-cassowary would contain something like (if you excuse some pseudo-code):

ExternalProject(Rhea)
ExternalProject(aqt-cassowary 
    DEPENDS Rhea
)