FindProtobuf: Add PROTOC_EXE option to protobuf_generate

This option was added to protobuf's upstream cmake package.

Help/release/dev/FindProtobuf-protoc-exe-option.rst

@@ -0,0 +1,5 @@
+FindProtobuf-protoc-exe-option
+------------------------------
+
+* The :module:`FindProtobuf` module :command:`protobuf_generate` command
+  gained a ``PROTOC_EXE`` option to specify a custom ``protoc`` executable.

Modules/FindProtobuf.cmake

@@ -164,6 +164,7 @@ Example:
         [IMPORT_DIRS <dir>...]
         [GENERATE_EXTENSIONS <extension>...]
         [PROTOC_OPTIONS <option>...]
+        [PROTOC_EXE <executable>]
         [APPEND_PATH])
 
   ``APPEND_PATH``
@@ -223,6 +224,12 @@ Example:
 
     Additional arguments that are forwarded to protoc.
 
+  ``PROTOC_EXE <executable>``
+    .. versionadded:: 3.32
+
+    Command name, path, or CMake executable used to generate protobuf bindings.
+    If omitted, ``protobuf::protoc`` is used.
+
   Example::
 
     find_package(gRPC CONFIG REQUIRED)
@@ -243,7 +250,7 @@ cmake_policy(SET CMP0159 NEW) # file(STRINGS) with REGEX updates CMAKE_MATCH_<n>
 
 function(protobuf_generate)
   set(_options APPEND_PATH DESCRIPTORS)
-  set(_singleargs LANGUAGE OUT_VAR EXPORT_MACRO PROTOC_OUT_DIR PLUGIN PLUGIN_OPTIONS DEPENDENCIES)
+  set(_singleargs LANGUAGE OUT_VAR EXPORT_MACRO PROTOC_OUT_DIR PLUGIN PLUGIN_OPTIONS DEPENDENCIES PROTOC_EXE)
   if(COMMAND target_sources)
     list(APPEND _singleargs TARGET)
   endif()
@@ -312,10 +319,14 @@ function(protobuf_generate)
     return()
   endif()
 
-  if(NOT TARGET protobuf::protoc)
-    message(SEND_ERROR "protoc executable not found. "
-            "Please define the Protobuf_PROTOC_EXECUTABLE variable or ensure that protoc is in CMake's search path.")
-    return()
+  if(NOT protobuf_generate_PROTOC_EXE)
+    if(NOT TARGET protobuf::protoc)
+      message(SEND_ERROR "protoc executable not found. "
+        "Please define the Protobuf_PROTOC_EXECUTABLE variable, or pass PROTOC_EXE to protobuf_generate, or ensure that protoc is in CMake's search path.")
+      return()
+    endif()
+    # Default to using the CMake executable
+    set(protobuf_generate_PROTOC_EXE protobuf::protoc)
   endif()
 
   if(protobuf_generate_APPEND_PATH)
@@ -388,7 +399,7 @@ function(protobuf_generate)
 
     add_custom_command(
       OUTPUT ${_generated_srcs}
-      COMMAND protobuf::protoc
+      COMMAND ${protobuf_generate_PROTOC_EXE}
       ARGS ${protobuf_generate_PROTOC_OPTIONS} --${protobuf_generate_LANGUAGE}_out ${_plugin_options}:${protobuf_generate_PROTOC_OUT_DIR} ${_plugin} ${_dll_desc_out} ${_protobuf_include_path} ${_abs_file}
       DEPENDS ${_abs_file} protobuf::protoc ${protobuf_generate_DEPENDENCIES}
       COMMENT ${_comment}

Tests/FindProtobuf/CMakeLists.txt

@@ -9,3 +9,4 @@ add_test(NAME FindProtobuf.Test COMMAND
   "-DCMake_TEST_FindProtobuf_gRPC=${CMake_TEST_FindProtobuf_gRPC}"
   --test-command ${CMAKE_CTEST_COMMAND} -V -C $<CONFIGURATION>
   )
+set_property(TEST FindProtobuf.Test PROPERTY FAIL_REGULAR_EXPRESSION PROTOC_EXE)

Tests/FindProtobuf/Test/CMakeLists.txt

@@ -70,7 +70,7 @@ if(CMake_TEST_FindProtobuf_gRPC)
   # NOTE: with IMPORT_DIRS msgs/, generated files will be placed under ${CMAKE_CURRENT_BINARY_DIR}/grpc/
   target_include_directories(msgs_grpc_IMPORT_DIRS PUBLIC ${CMAKE_CURRENT_BINARY_DIR} ${CMAKE_CURRENT_BINARY_DIR}/grpc/)
   target_link_libraries(msgs_grpc_IMPORT_DIRS PUBLIC ${Protobuf_LIBRARIES})
-  protobuf_generate(TARGET msgs_grpc_IMPORT_DIRS LANGUAGE cpp IMPORT_DIRS msgs/)
+  protobuf_generate(TARGET msgs_grpc_IMPORT_DIRS LANGUAGE cpp IMPORT_DIRS msgs/ PROTOC_EXE ${Protobuf_PROTOC_EXECUTABLE})
   protobuf_generate(TARGET msgs_grpc_IMPORT_DIRS LANGUAGE grpc IMPORT_DIRS msgs/ GENERATE_EXTENSIONS .grpc.pb.h .grpc.pb.cc PLUGIN "protoc-gen-grpc=${gRPC_CPP_PLUGIN}")
   add_executable(test_generate_grpc_IMPORT_DIRS main-generate-grpc.cxx)
   target_link_libraries(test_generate_grpc_IMPORT_DIRS PRIVATE msgs_grpc_IMPORT_DIRS)