GENERATED prop: Check CMP0118 policy and warn in certain situations

* Adding tests for CMP0118 being unset (aka set to `WARN`).
* Adjusting the (unrelated) RunCMake.CMP0026 test to set CMP0118 to
  `NEW`,
* Adjusting the (unrelated) RunCMake.Ninja test to set CMP0118 to `OLD`.
* Adjusting the (unrelated) RunCMake.FileAPI test to set CMP0118 to
  `OLD`.

Note:
Setting CMP0118 to `NEW` and modifying the `GENERATED` property with
`set_property` or `set_source_files_properties` will currently NOT set
that property because the implementation is still to come.

1 files changed, 13 insertions, 0 deletions

diff --git a/Source/cmSetPropertyCommand.h b/Source/cmSetPropertyCommand.h
index 01bde65..05c4873 100644
--- a/Source/cmSetPropertyCommand.h
+++ b/Source/cmSetPropertyCommand.h
@@ -9,6 +9,7 @@
 
 class cmMakefile;
 class cmExecutionStatus;
+class cmSourceFile;
 
 bool cmSetPropertyCommand(std::vector<std::string> const& args,
                           cmExecutionStatus& status);
@@ -39,4 +40,16 @@ void MakeSourceFilePathsAbsoluteIfNeeded(
   std::vector<std::string>& source_files_absolute_paths,
   std::vector<std::string>::const_iterator files_it_begin,
   std::vector<std::string>::const_iterator files_it_end, bool needed);
+
+enum class PropertyOp
+{
+  Remove,
+  Set,
+  Append,
+  AppendAsString
+};
+
+bool HandleAndValidateSourceFilePropertyGENERATED(
+  cmSourceFile* sf, std::string const& propertyValue,
+  PropertyOp op = PropertyOp::Set);
 }