Updating the engine.json.in template for the cmake INSTALL target to add the list of external subdirectories to allow the installed layout to access the subdirectories via it's engine.json file

cmake/EngineJson.cmake

@@ -13,6 +13,8 @@
 
 include_guard()
 
+set(LY_EXTERNAL_SUBDIRS "" CACHE STRING "List of subdirectories to recurse into when running cmake against the engine's CMakeLists.txt")
+
 #! read_engine_external_subdirs
 # Read the external subdirectories from the engine.json file
 # External subdirectories are any folders with CMakeLists.txt in them

cmake/Platform/Common/Install_common.cmake

@@ -224,6 +224,16 @@ function(ly_setup_cmake_install)
         REGEX "Platform\/.*\/BuiltInPackages_.*\.cmake" EXCLUDE
     )
 
+    # Transform the LY_EXTERNAL_SUBDIRS list into a json array
+    set(LY_INSTALL_EXTERNAL_SUBDIRS "[]")
+    set(external_subdir_index "0")
+    foreach(external_subdir ${LY_EXTERNAL_SUBDIRS})
+        math(EXPR external_subdir_index "${external_subdir_index} + 1")
+        file(RELATIVE_PATH engine_rel_external_subdir ${LY_ROOT_FOLDER} ${external_subdir})
+        string(JSON LY_INSTALL_EXTERNAL_SUBDIRS ERROR_VARIABLE external_subdir_error SET ${LY_INSTALL_EXTERNAL_SUBDIRS}
+        ${external_subdir_index} "\"${engine_rel_external_subdir}\"")
+    endforeach()
+
     configure_file(${LY_ROOT_FOLDER}/cmake/install/engine.json.in ${CMAKE_CURRENT_BINARY_DIR}/cmake/engine.json @ONLY)
 
     install(

cmake/install/engine.json.in

@@ -1,8 +1,11 @@
 {
     "engine_name": "@LY_VERSION_ENGINE_NAME@",
-    "restricted": "o3de",
+    "restricted_name": "o3de",
     "FileVersion": 1,
     "O3DEVersion": "@LY_VERSION_STRING@",
     "O3DECopyrightYear": @LY_VERSION_COPYRIGHT_YEAR@,
-    "O3DEBuildNumber": @LY_VERSION_BUILD_NUMBER@
+    "O3DEBuildNumber": @LY_VERSION_BUILD_NUMBER@,
+    "external_subdirectories": @LY_INSTALL_EXTERNAL_SUBDIRS@,
+    "projects": [@LY_INSTALL_PROJECTS@],
+    "templates": [@LY_INSTALL_TEMPLATES@]
 }