Improve the errors in EngineFinder.cmake (#4713)

* Improve the errors in EngineFinder.cmake

Added additional info on one of the errors to help users resolve the
issue (engine registration).
Improved readability of the errors.

Signed-off-by: amzn-phist <52085794+amzn-phist@users.noreply.github.com>

* Adds another error message to EngineFinder.cmake

An error message where the user's manifest is present and valid
but no matching engine name was found has been added.

Signed-off-by: amzn-phist <52085794+amzn-phist@users.noreply.github.com>

Templates/DefaultProject/Template/EngineFinder.cmake

@@ -18,7 +18,7 @@ set_property(DIRECTORY APPEND PROPERTY CMAKE_CONFIGURE_DEPENDS ${CMAKE_CURRENT_L
 
 string(JSON LY_ENGINE_NAME_TO_USE ERROR_VARIABLE json_error GET ${project_json} engine)
 if(json_error)
-    message(FATAL_ERROR "Unable to read key 'engine' from 'project.json', error: ${json_error}")
+    message(FATAL_ERROR "Unable to read key 'engine' from 'project.json'\nError: ${json_error}")
 endif()
 
 if(CMAKE_MODULE_PATH)
@@ -27,7 +27,7 @@ if(CMAKE_MODULE_PATH)
             file(READ ${module_path}/../engine.json engine_json)
             string(JSON engine_name ERROR_VARIABLE json_error GET ${engine_json} engine_name)
             if(json_error)
-                message(FATAL_ERROR "Unable to read key 'engine_name' from 'engine.json', error: ${json_error}")
+                message(FATAL_ERROR "Unable to read key 'engine_name' from 'engine.json'\nError: ${json_error}")
             endif()
             if(LY_ENGINE_NAME_TO_USE STREQUAL engine_name)
                 return() # Engine being forced through CMAKE_MODULE_PATH
@@ -42,6 +42,11 @@ else()
     set(manifest_path $ENV{HOME}/.o3de/o3de_manifest.json) # Unix
 endif()
 
+set(registration_error [=[
+Engine registration is required before configuring a project.
+Run 'scripts/o3de register --this-engine' from the engine root.
+]=])
+
 # Read the ~/.o3de/o3de_manifest.json file and look through the 'engines_path' object.
 # Find a key that matches LY_ENGINE_NAME_TO_USE and use that as the engine path.
 if(EXISTS ${manifest_path})
@@ -50,36 +55,38 @@ if(EXISTS ${manifest_path})
 
     string(JSON engines_path_count ERROR_VARIABLE json_error LENGTH ${manifest_json} engines_path)
     if(json_error)
-        message(FATAL_ERROR "Unable to read key 'engines_path' from '${manifest_path}', error: ${json_error}")
+        message(FATAL_ERROR "Unable to read key 'engines_path' from '${manifest_path}'\nError: ${json_error}\n${registration_error}")
     endif()
 
     string(JSON engines_path_type ERROR_VARIABLE json_error TYPE ${manifest_json} engines_path)
     if(json_error OR NOT ${engines_path_type} STREQUAL "OBJECT")
-        message(FATAL_ERROR "Type of 'engines_path' in '${manifest_path}' is not a JSON Object, error: ${json_error}")
+        message(FATAL_ERROR "Type of 'engines_path' in '${manifest_path}' is not a JSON Object\nError: ${json_error}")
     endif()
 
     math(EXPR engines_path_count "${engines_path_count}-1")
     foreach(engine_path_index RANGE ${engines_path_count})
         string(JSON engine_name ERROR_VARIABLE json_error MEMBER ${manifest_json} engines_path ${engine_path_index})
         if(json_error)
-            message(FATAL_ERROR "Unable to read 'engines_path/${engine_path_index}' from '${manifest_path}', error: ${json_error}")
+            message(FATAL_ERROR "Unable to read 'engines_path/${engine_path_index}' from '${manifest_path}'\nError: ${json_error}")
         endif()
 
         if(LY_ENGINE_NAME_TO_USE STREQUAL engine_name)
             string(JSON engine_path ERROR_VARIABLE json_error GET ${manifest_json} engines_path ${engine_name})
             if(json_error)
-                message(FATAL_ERROR "Unable to read value from 'engines_path/${engine_name}', error: ${json_error}")
+                message(FATAL_ERROR "Unable to read value from 'engines_path/${engine_name}'\nError: ${json_error}")
             endif()
 
             if(engine_path)
                 list(APPEND CMAKE_MODULE_PATH "${engine_path}/cmake")
-                break()
+                return()
             endif()
         endif()
     endforeach()
+    
+    message(FATAL_ERROR "The project.json uses engine name '${LY_ENGINE_NAME_TO_USE}' but no engine with that name has been registered.\n${registration_error}")
 else()
     # If the user is passing CMAKE_MODULE_PATH we assume thats where we will find the engine
     if(NOT CMAKE_MODULE_PATH)
-        message(FATAL_ERROR "Engine registration is required before configuring a project.  Please register an engine by running 'scripts/o3de register --this-engine'")
+        message(FATAL_ERROR "O3DE Manifest file not found.\n${registration_error}")
     endif()
 endif()

Templates/MinimalProject/Template/EngineFinder.cmake

@@ -18,7 +18,7 @@ set_property(DIRECTORY APPEND PROPERTY CMAKE_CONFIGURE_DEPENDS ${CMAKE_CURRENT_L
 
 string(JSON LY_ENGINE_NAME_TO_USE ERROR_VARIABLE json_error GET ${project_json} engine)
 if(json_error)
-    message(FATAL_ERROR "Unable to read key 'engine' from 'project.json', error: ${json_error}")
+    message(FATAL_ERROR "Unable to read key 'engine' from 'project.json'\nError: ${json_error}")
 endif()
 
 if(CMAKE_MODULE_PATH)
@@ -27,7 +27,7 @@ if(CMAKE_MODULE_PATH)
             file(READ ${module_path}/../engine.json engine_json)
             string(JSON engine_name ERROR_VARIABLE json_error GET ${engine_json} engine_name)
             if(json_error)
-                message(FATAL_ERROR "Unable to read key 'engine_name' from 'engine.json', error: ${json_error}")
+                message(FATAL_ERROR "Unable to read key 'engine_name' from 'engine.json'\nError: ${json_error}")
             endif()
             if(LY_ENGINE_NAME_TO_USE STREQUAL engine_name)
                 return() # Engine being forced through CMAKE_MODULE_PATH
@@ -42,6 +42,11 @@ else()
     set(manifest_path $ENV{HOME}/.o3de/o3de_manifest.json) # Unix
 endif()
 
+set(registration_error [=[
+Engine registration is required before configuring a project.
+Run 'scripts/o3de register --this-engine' from the engine root.
+]=])
+
 # Read the ~/.o3de/o3de_manifest.json file and look through the 'engines_path' object.
 # Find a key that matches LY_ENGINE_NAME_TO_USE and use that as the engine path.
 if(EXISTS ${manifest_path})
@@ -50,36 +55,38 @@ if(EXISTS ${manifest_path})
 
     string(JSON engines_path_count ERROR_VARIABLE json_error LENGTH ${manifest_json} engines_path)
     if(json_error)
-        message(FATAL_ERROR "Unable to read key 'engines_path' from '${manifest_path}', error: ${json_error}")
+        message(FATAL_ERROR "Unable to read key 'engines_path' from '${manifest_path}'\nError: ${json_error}\n${registration_error}")
     endif()
 
     string(JSON engines_path_type ERROR_VARIABLE json_error TYPE ${manifest_json} engines_path)
     if(json_error OR NOT ${engines_path_type} STREQUAL "OBJECT")
-        message(FATAL_ERROR "Type of 'engines_path' in '${manifest_path}' is not a JSON Object, error: ${json_error}")
+        message(FATAL_ERROR "Type of 'engines_path' in '${manifest_path}' is not a JSON Object\nError: ${json_error}")
     endif()
 
     math(EXPR engines_path_count "${engines_path_count}-1")
     foreach(engine_path_index RANGE ${engines_path_count})
         string(JSON engine_name ERROR_VARIABLE json_error MEMBER ${manifest_json} engines_path ${engine_path_index})
         if(json_error)
-            message(FATAL_ERROR "Unable to read 'engines_path/${engine_path_index}' from '${manifest_path}', error: ${json_error}")
+            message(FATAL_ERROR "Unable to read 'engines_path/${engine_path_index}' from '${manifest_path}'\nError: ${json_error}")
         endif()
 
         if(LY_ENGINE_NAME_TO_USE STREQUAL engine_name)
             string(JSON engine_path ERROR_VARIABLE json_error GET ${manifest_json} engines_path ${engine_name})
             if(json_error)
-                message(FATAL_ERROR "Unable to read value from 'engines_path/${engine_name}', error: ${json_error}")
+                message(FATAL_ERROR "Unable to read value from 'engines_path/${engine_name}'\nError: ${json_error}")
             endif()
 
             if(engine_path)
                 list(APPEND CMAKE_MODULE_PATH "${engine_path}/cmake")
-                break()
+                return()
             endif()
         endif()
     endforeach()
+    
+    message(FATAL_ERROR "The project.json uses engine name '${LY_ENGINE_NAME_TO_USE}' but no engine with that name has been registered.\n${registration_error}")
 else()
     # If the user is passing CMAKE_MODULE_PATH we assume thats where we will find the engine
     if(NOT CMAKE_MODULE_PATH)
-        message(FATAL_ERROR "Engine registration is required before configuring a project.  Please register an engine by running 'scripts/o3de register --this-engine'")
+        message(FATAL_ERROR "O3DE Manifest file not found.\n${registration_error}")
     endif()
 endif()