Use namespaced absl::abseil_dll imported target instead of abseil_dll…

… to correctly propagate CMake usage requirements defined in abseil build on Windows (#162)

automerged PR by conda-forge/automerge-action

recipe/cmake_test/CMakeLists.txt

@@ -1,6 +1,26 @@
 project(cf_dummy LANGUAGES C CXX)
 cmake_minimum_required(VERSION 3.12)
-# CMake seems to prefer its own FindProtobuf to the
-# protobuf-config.cmake being distributed by this
-# feedstock; make sure things work
-find_package(Protobuf REQUIRED)
+# We need to specify CONFIG to make sure that CMake
+# uses protobuf-config.cmake instead of relying on its
+# own FindProtobuf.cmake that does not know about
+# abseil transitive depedendency and about C++ version
+# required, see https://github.com/conda-forge/conda-forge-pinning-feedstock/issues/4075#issuecomment-1569242816
+find_package(Protobuf CONFIG REQUIRED)
+
+file(WRITE ${CMAKE_CURRENT_BINARY_DIR}/struct_example.cc
+"
+
+#include <iostream>
+
+#include <google/protobuf/struct.pb.h>
+
+int main()
+{
+    google::protobuf::Struct myStruct;
+}
+
+"
+)
+
+add_executable(struct_example ${CMAKE_CURRENT_BINARY_DIR}/struct_example.cc)
+target_link_libraries(struct_example PRIVATE protobuf::libprotobuf)

recipe/meta.yaml

@@ -21,9 +21,11 @@ source:
       - patches/0004-always-look-for-shared-abseil-builds.patch
       - patches/0005-be-more-lenient-with-abseil-version.patch
       - patches/0006-add-PROTOBUF_EXPORT-for-google-protobuf-io-SafeDoubl.patch
+      # backport https://github.com/protocolbuffers/protobuf/pull/12978
+      - patches/0007-use-namespaced-abseil-dll-imported-target-backport-12978.patch
 
 build:
-  number: 2
+  number: 3
 
 outputs:
   - name: libprotobuf
@@ -87,10 +89,11 @@ outputs:
         # binary
         - protoc --help
 
-        # more CMake integration (CMake uses its own FindProtobuf)
+        # more CMake integration
         - cd cmake_test
         - cmake -GNinja $CMAKE_ARGS .   # [unix]
         - cmake -GNinja %CMAKE_ARGS% .  # [win]
+        - cmake --build .
 
   - name: libprotobuf-static
     script: build-lib.sh   # [unix]
@@ -129,10 +132,11 @@ outputs:
         - if not exist %LIBRARY_LIB%\{{ each_lib }}-static.lib exit 1  # [win]
         {% endfor %}
 
-        # more CMake integration (CMake uses its own FindProtobuf)
+        # more CMake integration
         - cd cmake_test
         - cmake -GNinja $CMAKE_ARGS .   # [unix]
         - cmake -GNinja %CMAKE_ARGS% .  # [win]
+        - cmake --build .
 
 about:
   home: https://developers.google.com/protocol-buffers/

recipe/patches/0007-use-namespaced-abseil-dll-imported-target-backport-12978.patch

@@ -0,0 +1,26 @@
+diff --git a/cmake/abseil-cpp.cmake b/cmake/abseil-cpp.cmake
+index e7bfb2b15f8..c668f4d9b01 100644
+--- a/cmake/abseil-cpp.cmake
++++ b/cmake/abseil-cpp.cmake
+@@ -39,8 +39,19 @@ set(_protobuf_FIND_ABSL "if(NOT TARGET absl::strings)\n  find_package(absl CONFI
+
+ if (BUILD_SHARED_LIBS AND MSVC)
+   # On MSVC Abseil is bundled into a single DLL.
+-  set(protobuf_ABSL_USED_TARGETS abseil_dll)
+-
++  # This condition is necessary as of abseil 20230125.3 when abseil is consumed via add_subdirectory,
++  # the abseil_dll target  is named abseil_dll, while if abseil is consumed via find_package, the target
++  # is called absl::abseil_dll
++  # Once https://github.com/abseil/abseil-cpp/pull/1466 is merged and released in the minimum version of 
++  # abseil required by protobuf, it is possible to always link absl::abseil_dll and absl::abseil_test_dll
++  # and remove the if
++  if(protobuf_ABSL_PROVIDER STREQUAL "package")
++    set(protobuf_ABSL_USED_TARGETS absl::abseil_dll)
++  else()
++    set(protobuf_ABSL_USED_TARGETS abseil_dll)
++  endif()
++  # Not all build of abseil found by find_package provide the absl::abseil_test_dll target, so for 
++  # it we stick to the non-namespaced definition
+   set(protobuf_ABSL_USED_TEST_TARGETS abseil_test_dll)
+ else()
+   set(protobuf_ABSL_USED_TARGETS