build: add golang to cmake

Problem: the new cmake build system needs to compile go tests for bindings
Solution: use add_custom_command to do a build of the test.

CMakeLists.txt

@@ -174,6 +174,11 @@ if(ENABLE_COVERAGE)
   SET( CMAKE_EXE_LINKER_FLAGS  "${CMAKE_EXE_LINKER_FLAGS} ${COVERAGE_FLAGS}" )
 endif()
 
+if(DEFINED ENV{WITH_GO})
+  message(STATUS "WITH_GO detected in main CMakeLists.txt to build go bindings")
+  include(GolangSimple)
+endif()
+
 include_directories(.)
 add_subdirectory( etc )
 add_subdirectory( src )

README.md

@@ -111,6 +111,30 @@ make check
 make install
 ```
 
+To build go bindings, you will need go (tested with 1.19.10) available, and then:
+
+```bash
+export WITH_GO=yes
+./configure
+make
+```
+
+To run just one test, you can cd into t
+
+```bash
+$ ./t9001-golang-basic.t 
+ok 1 - match allocate 1 slot: 1 socket: 1 core (pol=default)
+ok 2 - match allocate 2 slots: 2 sockets: 5 cores 1 gpu 6 memory
+# passed all 2 test(s)
+1..2
+```
+
+To run full tests (more robust and mimics what happens in CI) you can do:
+
+```bash
+make check
+```
+
 ##### Flux Instance
 
 The examples below walk through exercising functioning flux-sched modules (i.e.,

cmake/GolangSimple.cmake

@@ -0,0 +1,30 @@
+set(CUSTOM_GO_PATH "${CMAKE_SOURCE_DIR}/resource/reapi/bindings/go")
+set(GOPATH "${CMAKE_CURRENT_BINARY_DIR}/go")
+
+# This probably isn't necessary, although if we could build fluxcli into it maybe
+file(MAKE_DIRECTORY ${GOPATH})
+
+# ADD_GO_INSTALLABLE_PROGRAM builds a custom go program (primarily for testing)
+function(BUILD_GO_PROGRAM NAME MAIN_SRC CGO_CFLAGS CGO_LIBRARY_FLAGS)
+  message(STATUS "GOPATH: ${GOPATH}")
+  message(STATUS "CGO_LDFLAGS: ${CGO_LIBRARY_FLAGS}")
+  get_filename_component(MAIN_SRC_ABS ${MAIN_SRC} ABSOLUTE)
+  add_custom_target(${NAME})
+
+  # IMPORTANT: the trick to getting *spaces* to render in COMMAND is to convert them to ";"
+  # string(REPLACE <match-string> <replace-string> <out-var> <input>...)
+  STRING(REPLACE " " ";" CGO_LIBRARY_FLAGS ${CGO_LIBRARY_FLAGS})  
+  add_custom_command(TARGET ${NAME}
+                    COMMAND GOPATH=${GOPATH}:${CUSTOM_GO_PATH} GOOS=linux G0111MODULE=off CGO_CFLAGS="${CGO_CFLAGS}" CGO_LDFLAGS='${CGO_LIBRARY_FLAGS}' go build -ldflags '-w'
+                    -o "${CMAKE_CURRENT_SOURCE_DIR}/${NAME}"
+                    ${CMAKE_GO_FLAGS} ${MAIN_SRC}
+                    WORKING_DIRECTORY ${CMAKE_CURRENT_LIST_DIR}
+                    DEPENDS ${MAIN_SRC_ABS}
+                    COMMENT "Building Go library")
+  foreach(DEP ${ARGN})
+    add_dependencies(${NAME} ${DEP})
+  endforeach()
+
+  add_custom_target(${NAME}_all ALL DEPENDS ${NAME})
+  install(PROGRAMS ${CMAKE_CURRENT_BINARY_DIR}/${NAME} DESTINATION bin)
+endfunction(BUILD_GO_PROGRAM)

resource/reapi/bindings/CMakeLists.txt

@@ -18,3 +18,8 @@ add_library ( reapi_module STATIC
 target_link_libraries(reapi_module PRIVATE
     flux::core
     )
+
+if(DEFINED ENV{WITH_GO})
+    message(STATUS "WITH_GO is set to build go bindings")
+    add_subdirectory( go )
+endif()

resource/reapi/bindings/go/CMakeLists.txt

@@ -0,0 +1 @@
+add_subdirectory( src )

resource/reapi/bindings/go/src/CMakeLists.txt

@@ -0,0 +1 @@
+add_subdirectory( test )

resource/reapi/bindings/go/src/test/CMakeLists.txt

@@ -0,0 +1,17 @@
+set(TARGET main)
+set(SRCS main.go)
+set(CGO_CFLAGS "-I${CMAKE_BINARY_DIR}/resource/reapi/bindings/c")
+
+# This is currently passed but not used because when passed into add_custom_command the spaces are escaped
+set(CGO_LIBRARY_FLAGS "-Wl,-R ${CMAKE_BINARY_DIR}/resource -L${CMAKE_BINARY_DIR}/resource/reapi/bindings -L${CMAKE_BINARY_DIR}/resource/libjobspec -ljobspec_conv -lreapi_cli -L${CMAKE_BINARY_DIR}/resource -lresource -lflux-idset -lstdc++ -lczmq -ljansson -lhwloc -lboost_system -lflux-hostlist -lboost_graph -lyaml-cpp")
+
+# This ensures the main binary is cleaned up
+set_directory_properties(
+    PROPERTIES
+      ADDITIONAL_CLEAN_FILES "${CMAKE_CURRENT_BINARY_DIR}/main"
+  )
+
+# GO_GET(go_redis github.com/hoisie/redis)
+#                          main      main.go  
+# We add the dependencies at the end so the build can run in parallel and we don't try to build this before they are ready!
+BUILD_GO_PROGRAM(${TARGET} ${SRCS} "${CGO_CFLAGS}" "${CGO_LIBRARY_FLAGS}" jobspec_conv reapi_module reapi_cli resource flux::core)