cmTargetPropCommandBase: check keywords after parsing

The following was disallowed:

   add_library(iface INTERFACE)
   target_link_libraries(iface PUBLIC)

just due to the mention of the `PUBLIC` keyword. Instead, only error if
there are actually `PUBLIC` dependencies specified (and analogously for
other restrictions).

Update tests to expect this new behavior.

1 files changed, 11 insertions, 9 deletions

diff --git a/Source/cmTargetPropCommandBase.cxx b/Source/cmTargetPropCommandBase.cxx
index 48348f37e5..1b8ee812fe 100644
--- a/Source/cmTargetPropCommandBase.cxx
+++ b/Source/cmTargetPropCommandBase.cxx
@@ -84,15 +84,6 @@ bool cmTargetPropCommandBase::ProcessContentArgs(
     this->SetError("called with invalid arguments");
     return false;
   }
-  if (this->Target->GetType() == cmStateEnums::INTERFACE_LIBRARY &&
-      scope != "INTERFACE") {
-    this->SetError("may only set INTERFACE properties on INTERFACE targets");
-    return false;
-  }
-  if (this->Target->IsImported() && scope != "INTERFACE") {
-    this->SetError("may only set INTERFACE properties on IMPORTED targets");
-    return false;
-  }
 
   ++argIndex;
 
@@ -105,6 +96,17 @@ bool cmTargetPropCommandBase::ProcessContentArgs(
     }
     content.push_back(args[i]);
   }
+  if (!content.empty()) {
+    if (this->Target->GetType() == cmStateEnums::INTERFACE_LIBRARY &&
+        scope != "INTERFACE") {
+      this->SetError("may only set INTERFACE properties on INTERFACE targets");
+      return false;
+    }
+    if (this->Target->IsImported() && scope != "INTERFACE") {
+      this->SetError("may only set INTERFACE properties on IMPORTED targets");
+      return false;
+    }
+  }
   return this->PopulateTargetProperies(scope, content, prepend, system);
 }