From 066e8a4557e7cbe98403bbf97b957f5f993f89c3 Mon Sep 17 00:00:00 2001
From: Alexandru Croitor <alexandru.croitor@qt.io>
Date: Thu, 9 Apr 2020 09:59:35 +0200
Subject: [PATCH] CMake: Handle missing packages in project compile tests

If a find_package() in a try_compile project doesn't find a package,
and we then link against a non-existent target, the configuration
failure of the compile test also fails the configuration of the
project.

To avoid that, separate library targets from non-targets, and make sure
to only link against the targets if they exist.

pro2cmake now outputs modified compile test project code which iterates
over targets and non-target libraries, and links against them when
needed.

Change-Id: Ib0f4b5f07af13929c42d01a661df2cabdf9b926b
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>
---
 cmake/QtFeature.cmake   | 20 +++++++++++++++++++-
 util/cmake/pro2cmake.py |  8 +++++++-
 2 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/cmake/QtFeature.cmake b/cmake/QtFeature.cmake
index b2d993647f3..4cf7c0f9466 100644
--- a/cmake/QtFeature.cmake
+++ b/cmake/QtFeature.cmake
@@ -699,7 +699,25 @@ function(qt_config_compile_test name)
 
         # Pass which libraries need to be linked against.
         if(arg_LIBRARIES)
-            list(APPEND flags "-DQT_CONFIG_COMPILE_TEST_LIBRARIES:STRING=${arg_LIBRARIES}")
+            set(link_flags "")
+            set(library_targets "")
+            # Separate targets from link flags or paths. This is to prevent configuration failures
+            # when the targets are not found due to missing packages.
+            foreach(lib ${arg_LIBRARIES})
+                string(FIND "${lib}" "::" is_library_target)
+                if(is_library_target EQUAL -1)
+                    list(APPEND link_flags "${lib}")
+                else()
+                    list(APPEND library_targets "${lib}")
+                endif()
+            endforeach()
+            if(link_flags)
+                list(APPEND flags "-DQT_CONFIG_COMPILE_TEST_LIBRARIES:STRING=${link_flags}")
+            endif()
+            if(library_targets)
+                list(APPEND flags
+                     "-DQT_CONFIG_COMPILE_TEST_LIBRARY_TARGETS:STRING=${library_targets}")
+            endif()
         endif()
 
         try_compile(HAVE_${name} "${CMAKE_BINARY_DIR}/config.tests/${name}" "${arg_PROJECT_PATH}"
diff --git a/util/cmake/pro2cmake.py b/util/cmake/pro2cmake.py
index 87e2593d00e..92b7597dcd7 100755
--- a/util/cmake/pro2cmake.py
+++ b/util/cmake/pro2cmake.py
@@ -3948,7 +3948,13 @@ endforeach()
 if(QT_CONFIG_COMPILE_TEST_LIBRARIES)
     link_libraries(${QT_CONFIG_COMPILE_TEST_LIBRARIES})
 endif()
-
+if(QT_CONFIG_COMPILE_TEST_LIBRARY_TARGETS)
+    foreach(lib ${QT_CONFIG_COMPILE_TEST_LIBRARY_TARGETS})
+        if(TARGET ${lib})
+            link_libraries(${lib})
+        endif()
+    endforeach()
+endif()
 """
     )
     cm_fh.write(f"{content}\n")