Add new flow-control commands for variables and policies scopes management

Add block() and endblock() commands offering the capability to create
new scopes for variables and/or policies.

Fixes: #20171

1 files changed, 11 insertions, 0 deletions

diff --git a/Source/cmListFileCache.cxx b/Source/cmListFileCache.cxx
index 91157cbf03..6270c825f2 100644
--- a/Source/cmListFileCache.cxx
+++ b/Source/cmListFileCache.cxx
@@ -347,6 +347,7 @@ enum class NestingStateEnum
   Foreach,
   Function,
   Macro,
+  Block
 };
 
 struct NestingState
@@ -434,6 +435,16 @@ cm::optional<cmListFileContext> cmListFileParser::CheckNesting() const
         return cmListFileContext::FromListFileFunction(func, this->FileName);
       }
       stack.pop_back();
+    } else if (name == "block") {
+      stack.push_back({
+        NestingStateEnum::Block,
+        cmListFileContext::FromListFileFunction(func, this->FileName),
+      });
+    } else if (name == "endblock") {
+      if (!TopIs(stack, NestingStateEnum::Block)) {
+        return cmListFileContext::FromListFileFunction(func, this->FileName);
+      }
+      stack.pop_back();
     }
   }