Check required dependencies for gRPC before adding WrapgRPC library

Check required dependencies for gRPC, which are linked as
INTERFACE_LINK_LIBRARIES which results in error when trying to use
gRPC library.

Fixes: QTBUG-109372
Pick-to: 6.5
Change-Id: Ib1adb7f9aff3041c50fabaa47bf269081342a639
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>

cmake/FindWrapgRPC.cmake

@@ -17,11 +17,13 @@ if(TARGET Threads::Threads)
     qt_internal_disable_find_package_global_promotion(Threads::Threads)
 endif()
 
-set(__WrapgRPC_CMAKE_FIND_PACKAGE_PREFER_CONFIG_save ${CMAKE_FIND_PACKAGE_PREFER_CONFIG})
-set(CMAKE_FIND_PACKAGE_PREFER_CONFIG TRUE)
-find_package(gRPC ${__WrapgRPC_find_package_args})
-set(CMAKE_FIND_PACKAGE_PREFER_CONFIG ${__WrapgRPC_CMAKE_FIND_PACKAGE_PREFER_CONFIG_save})
-unset(__WrapgRPC_CMAKE_FIND_PACKAGE_PREFER_CONFIG_save)
+if(NOT TARGET gRPC::grpc++)
+    set(__WrapgRPC_CMAKE_FIND_PACKAGE_PREFER_CONFIG_save ${CMAKE_FIND_PACKAGE_PREFER_CONFIG})
+    set(CMAKE_FIND_PACKAGE_PREFER_CONFIG TRUE)
+    find_package(gRPC ${__WrapgRPC_find_package_args})
+    set(CMAKE_FIND_PACKAGE_PREFER_CONFIG ${__WrapgRPC_CMAKE_FIND_PACKAGE_PREFER_CONFIG_save})
+    unset(__WrapgRPC_CMAKE_FIND_PACKAGE_PREFER_CONFIG_save)
+endif()
 
 if(TARGET gRPC::grpc_cpp_plugin)
     qt_internal_disable_find_package_global_promotion(gRPC::grpc_cpp_plugin)
@@ -58,20 +60,38 @@ function(WrapgRPC_ensure_grpc_lib libname)
 endfunction()
 
 
-if(NOT TARGET gRPC::grpc OR NOT TARGET gRPC::grpc++)
+if(NOT TARGET gRPC::grpc++)
     find_package(PkgConfig QUIET)
     if(PkgConfig_FOUND)
-        WrapgRPC_ensure_grpc_lib(grpc)
         WrapgRPC_ensure_grpc_lib(grpc++)
     endif()
 endif()
 
 unset(WrapgRPC_ensure_grpc_lib)
 
-if(TARGET gRPC::grpc
-    AND TARGET gRPC::grpc++)
+if(TARGET gRPC::grpc++ AND TARGET gRPC::grpc)
+    ## Check all required target dependencies for gRPC
+    ## the gRPCConfig.cmake assumes that they are available in the system
+    ## and links them as INTERFACE_LINK_LIBRARIES,
+    ## which can result in error:
+    ## The link interface of target "gRPC::grpc" contains: <missing library>
+    set(__all_dependencies_found TRUE)
+    get_target_property(__all_dependencies_required gRPC::grpc INTERFACE_LINK_LIBRARIES)
+    foreach(__grpc_dep ${__all_dependencies_required})
+        if(NOT ${__grpc_dep} MATCHES ".*::.*")
+            continue()
+        endif()
+        if(NOT TARGET ${__grpc_dep})
+            message(WARNING "gRPC was found, but the ${__grpc_dep} dependency is missing.")
+            set(__all_dependencies_found FALSE)
+        endif()
+    endforeach()
+    if(NOT __all_dependencies_found)
+        return()
+    endif()
+
     add_library(WrapgRPC::WrapLibgRPC INTERFACE IMPORTED)
-    target_link_libraries(WrapgRPC::WrapLibgRPC INTERFACE gRPC::grpc gRPC::grpc++)
+    target_link_libraries(WrapgRPC::WrapLibgRPC INTERFACE gRPC::grpc++)
     get_target_property(Grpc_INCLUDE_PATH gRPC::grpc++ INTERFACE_INCLUDE_DIRECTORIES)
     set_property(GLOBAL PROPERTY WrapgRPC_INCLUDE_PATH "${Grpc_INCLUDE_PATH}")
 

tests/auto/grpc/client/CMakeLists.txt

@@ -1,6 +1,10 @@
 # Copyright (C) 2022 The Qt Company Ltd.
 # SPDX-License-Identifier: BSD-3-Clause
 
+if(NOT TARGET testserver)
+    return()
+endif()
+
 qt6_add_protobuf(tst_grpc_client_qtgrpc_gen
     OUTPUT_DIRECTORY
         "${CMAKE_CURRENT_BINARY_DIR}/qt_grpc_generated"

tests/auto/grpc/shared/test_server/CMakeLists.txt

@@ -1,9 +1,13 @@
 # Copyright (C) 2022 The Qt Company Ltd.
 # SPDX-License-Identifier: BSD-3-Clause
 
-find_package(WrapgRPCPlugin REQUIRED)
-find_package(WrapProtobuf REQUIRED)
-find_package(WrapgRPC REQUIRED)
+find_package(WrapgRPCPlugin)
+find_package(WrapProtobuf)
+find_package(WrapgRPC)
+
+if(NOT WrapgRPCPlugin_Found OR NOT WrapProtobuf_Found OR NOT WrapgRPC_Found)
+    return()
+endif()
 
 set(proto_files "${CMAKE_CURRENT_LIST_DIR}/../proto/testservice.proto")
 set(out_dir ${CMAKE_CURRENT_BINARY_DIR})

tests/auto/grpc/ssl_client/CMakeLists.txt

@@ -1,6 +1,10 @@
 # Copyright (C) 2022 The Qt Company Ltd.
 # SPDX-License-Identifier: BSD-3-Clause
 
+if(NOT TARGET securetestserver)
+    return()
+endif()
+
 qt6_add_protobuf(tst_grpc_ssl_client_qtgrpc_gen
     OUTPUT_DIRECTORY
         "${CMAKE_CURRENT_BINARY_DIR}/qt_grpc_generated"