Merge branch 'backport-3.17-automoc_timestamp_deps'

Source/cmQtAutoGenInitializer.cxx

@@ -1182,11 +1182,54 @@ bool cmQtAutoGenInitializer::InitAutogenTarget()
     if (useNinjaDepfile) {
       // Create a custom command that generates a timestamp file and
       // has a depfile assigned. The depfile is created by JobDepFilesMergeT.
+      //
+      // Also create an additional '_autogen_timestamp_deps' that the custom
+      // command will depend on. It will have no sources or commands to
+      // execute, but it will have dependencies that would originally be
+      // assigned to the pre-Qt 5.15 'autogen' target. These dependencies will
+      // serve as a list of order-only dependencies for the custom command,
+      // without forcing the custom command to re-execute.
+      //
+      // The dependency tree would then look like
+      // '_autogen_timestamp_deps (order-only)' <- '/timestamp' file <-
+      // '_autogen' target.
+      const auto timestampTargetName =
+        cmStrCat(this->GenTarget->GetName(), "_autogen_timestamp_deps");
+      std::vector<std::string> timestampTargetProvides;
+      cmCustomCommandLines timestampTargetCommandLines;
 
-      // Add additional autogen target dependencies
+      // Add additional autogen target dependencies to
+      // '_autogen_timestamp_deps'.
       for (const cmTarget* t : this->AutogenTarget.DependTargets) {
         dependencies.push_back(t->GetName());
       }
+
+      cmTarget* timestampTarget = this->LocalGen->AddUtilityCommand(
+        timestampTargetName, true, this->Dir.Work.c_str(),
+        /*byproducts=*/timestampTargetProvides,
+        /*depends=*/dependencies, timestampTargetCommandLines, false, nullptr);
+      this->LocalGen->AddGeneratorTarget(
+        cm::make_unique<cmGeneratorTarget>(timestampTarget, this->LocalGen));
+
+      // Set FOLDER property on the timestamp target, so it appears in the
+      // appropriate folder in an IDE or in the file api.
+      if (!this->TargetsFolder.empty()) {
+        timestampTarget->SetProperty("FOLDER", this->TargetsFolder);
+      }
+
+      // Make '/timestamp' file depend on '_autogen_timestamp_deps' and on the
+      // moc and uic executables (whichever are enabled).
+      dependencies.clear();
+      dependencies.push_back(timestampTargetName);
+
+      if (this->Moc.ExecutableTarget != nullptr) {
+        dependencies.push_back(this->Moc.ExecutableTarget->Target->GetName());
+      }
+      if (this->Uic.ExecutableTarget != nullptr) {
+        dependencies.push_back(this->Uic.ExecutableTarget->Target->GetName());
+      }
+
+      // Create the custom command that outputs the timestamp file.
       const char timestampFileName[] = "timestamp";
       const std::string outputFile =
         cmStrCat(this->Dir.Build, "/", timestampFileName);

Source/cmQtAutoMocUic.cxx

@@ -2163,7 +2163,9 @@ std::string escapeDependencyPath(cm::string_view path)
 void cmQtAutoMocUicT::JobDepFilesMergeT::Process()
 {
   if (Log().Verbose()) {
-    Log().Info(GenT::MOC, "Merging MOC dependencies");
+    Log().Info(GenT::MOC,
+               cmStrCat("Merging MOC dependencies into ",
+                        MessagePath(BaseConst().DepFile.c_str())));
   }
   auto processDepFile =
     [](const std::string& mocOutputFile) -> std::vector<std::string> {

Tests/RunCMake/CMakeLists.txt

@@ -142,6 +142,9 @@ if(CMAKE_GENERATOR MATCHES "Ninja")
   if(CMAKE_Fortran_COMPILER)
     list(APPEND Ninja_ARGS -DTEST_Fortran=1)
   endif()
+  if(CMake_TEST_Qt5 AND Qt5Core_FOUND)
+    list(APPEND Ninja_ARGS -DCMake_TEST_Qt5=1 -DCMAKE_TEST_Qt5Core_Version=${Qt5Core_VERSION})
+  endif()
   add_RunCMake_test(Ninja)
   set(NinjaMultiConfig_ARGS
     -DCYGWIN=${CYGWIN}

Tests/RunCMake/Ninja/Qt5AutoMocDeps.cmake

@@ -0,0 +1,9 @@
+enable_language(CXX)
+
+find_package(Qt5Core REQUIRED)
+
+set(CMAKE_AUTOMOC ON)
+
+add_library(simple_lib SHARED simple_lib.cpp)
+add_executable(app_with_qt app.cpp app_qt.cpp)
+target_link_libraries(app_with_qt PRIVATE simple_lib Qt5::Core)

Tests/RunCMake/Ninja/RunCMakeTest.cmake

@@ -138,6 +138,7 @@ ${ninja_stderr}
     message(FATAL_ERROR
       "top ninja build failed exited with status ${ninja_result}")
   endif()
+  set(ninja_stdout "${ninja_stdout}" PARENT_SCOPE)
 endfunction(run_ninja)
 
 function (run_LooseObjectDepends)
@@ -322,3 +323,23 @@ function (run_ChangeBuildType)
   run_ninja("${RunCMake_TEST_BINARY_DIR}" -w dupbuild=err)
 endfunction()
 run_ChangeBuildType()
+
+function(run_Qt5AutoMocDeps)
+  if(CMake_TEST_Qt5 AND CMAKE_TEST_Qt5Core_Version VERSION_GREATER_EQUAL 5.15.0)
+    set(RunCMake_TEST_BINARY_DIR ${RunCMake_BINARY_DIR}/Qt5AutoMocDeps-build)
+    run_cmake(Qt5AutoMocDeps)
+    unset(RunCMake_TEST_OPTIONS)
+    # Build the project.
+    run_ninja("${RunCMake_TEST_BINARY_DIR}")
+    # Touch just the library source file, which shouldn't cause a rerun of AUTOMOC
+    # for app_with_qt target.
+    touch("${RunCMake_SOURCE_DIR}/simple_lib.cpp")
+    # Build and assert that AUTOMOC was not run for app_with_qt.
+    run_ninja("${RunCMake_TEST_BINARY_DIR}")
+    if(ninja_stdout MATCHES "Automatic MOC for target app_with_qt")
+        message(FATAL_ERROR
+               "AUTOMOC should not have executed for 'app_with_qt' target:\nstdout:\n${ninja_stdout}")
+    endif()
+  endif()
+endfunction()
+run_Qt5AutoMocDeps()

Tests/RunCMake/Ninja/app.cpp

@@ -0,0 +1,6 @@
+int main(int argc, char* argv[])
+{
+  (void)argc;
+  (void)argv;
+  return 0;
+}

Tests/RunCMake/Ninja/app_qt.cpp

@@ -0,0 +1,11 @@
+#include <QObject>
+
+class Mango : public QObject
+{
+  Q_OBJECT
+public:
+Q_SIGNALS:
+  void eatFruit();
+};
+
+#include "app_qt.moc"

Tests/RunCMake/Ninja/simple_lib.cpp

@@ -0,0 +1,6 @@
+#ifdef _WIN32
+__declspec(dllexport)
+#endif
+  void dummy_symbol()
+{
+}