Autogen: Skip generated files for compatibility with CMake 3.8

The change in commit v3.9.0-rc1~464^2~8 (Autogen: Add AUTOMOC/UIC
support for generated source files, 2017-03-02) changes behavior of
existing projects that may not expect `AUTOGEN` on generated files and
do not yet set `SKIP_AUTOGEN` on them.  Disable the behavior change for
now to fix the regression for CMake 3.9.  We can restore it later with a
policy.

In order to keep the implementation and tests working, add an
undocumented property we can use in the tests to enable the behavior
before the policy is introduced.

Fixes: #17031
Issue: #16186

1 files changed, 7 insertions, 0 deletions

diff --git a/Source/cmQtAutoGeneratorInitializer.cxx b/Source/cmQtAutoGeneratorInitializer.cxx
index 6924ba2..cecf165 100644
--- a/Source/cmQtAutoGeneratorInitializer.cxx
+++ b/Source/cmQtAutoGeneratorInitializer.cxx
@@ -303,6 +303,13 @@ static void AcquireScanFiles(cmGeneratorTarget const* target,
         !(fileType == cmSystemTools::HEADER_FILE_FORMAT)) {
       continue;
     }
+    if (PropertyEnabled(sf, "GENERATED") &&
+        !target->GetPropertyAsBool("__UNDOCUMENTED_AUTOGEN_GENERATED_FILES")) {
+      // FIXME: Add a policy whose NEW behavior allows generated files.
+      // The implementation already works.  We disable it here to avoid
+      // changing behavior for existing projects that do not expect it.
+      continue;
+    }
     const std::string absFile =
       cmsys::SystemTools::GetRealPath(sf->GetFullPath());
     // Skip flags