From 09a3fdec9b0a51a985f74c7dcab5a0f993019859 Mon Sep 17 00:00:00 2001
From: Craig Scott <craig.scott@crascit.com>
Date: Mon, 5 May 2025 20:28:03 +1000
Subject: [PATCH] Add CODEGEN keyword to add_custom_command() if supported

If using CMake 3.31 or later, add_custom_command() supports a CODEGEN
keyword. It requires policy CMP0171 to be set to NEW to be recognized.
Add the CODEGEN keyword to these calls if we can so that consumers can
build the `codegen` CMake target to ensure code generation has been
performed without having to actually compile the generated code. This is
useful for linting CI jobs like clang-tidy.
---
 CMakeRC.cmake | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/CMakeRC.cmake b/CMakeRC.cmake
index 6a5147a..1167281 100644
--- a/CMakeRC.cmake
+++ b/CMakeRC.cmake
@@ -37,6 +37,11 @@ set(_version 2.0.0)
 cmake_minimum_required(VERSION 3.12)
 include(CMakeParseArguments)
 
+# Enable use of CODEGEN keyword in add_custom_command() calls if available
+if(POLICY CMP0171)
+    cmake_policy(SET CMP0171 NEW)
+endif()
+
 if(COMMAND cmrc_add_resource_library)
     if(NOT DEFINED _CMRC_VERSION OR NOT (_version STREQUAL _CMRC_VERSION))
         message(WARNING "More than one CMakeRC version has been included in this project.")
@@ -487,10 +492,16 @@ function(cmrc_add_resource_library name)
     string(REPLACE "\n        " "\n" cpp_content "${cpp_content}")
     file(GENERATE OUTPUT "${lib_tmp_cpp}" CONTENT "${cpp_content}")
     get_filename_component(libcpp "${libdir}/lib.cpp" ABSOLUTE)
+    if(POLICY CMP0171)
+        set(maybe_CODEGEN CODEGEN)
+    else()
+        set(maybe_CODEGEN "")
+    endif()
     add_custom_command(OUTPUT "${libcpp}"
         DEPENDS "${lib_tmp_cpp}" "${cmrc_hpp}"
         COMMAND ${CMAKE_COMMAND} -E copy_if_different "${lib_tmp_cpp}" "${libcpp}"
         COMMENT "Generating ${name} resource loader"
+        ${maybe_CODEGEN}
         )
     # Generate the actual static library. Each source file is just a single file
     # with a character array compiled in containing the contents of the
@@ -619,6 +630,11 @@ function(cmrc_add_resources name)
 endfunction()
 
 function(_cmrc_generate_intermediate_cpp lib_ns symbol outfile infile)
+    if(POLICY CMP0171)
+        set(maybe_CODEGEN CODEGEN)
+    else()
+        set(maybe_CODEGEN "")
+    endif()
     add_custom_command(
         # This is the file we will generate
         OUTPUT "${outfile}"
@@ -633,6 +649,7 @@ function(_cmrc_generate_intermediate_cpp lib_ns symbol outfile infile)
                 "-DOUTPUT_FILE=${outfile}"
                 -P "${_CMRC_SCRIPT}"
         COMMENT "Generating intermediate file for ${infile}"
+        ${maybe_CODEGEN}
     )
 endfunction()