block: Fix variable scope protection from modification by subdirectories

When `cmStateSnapshot::RaiseScope` raises a variable in to a parent
directory scope, it uses `GetBuildsystemDirectoryParent` to find the
current top-most scope on the directory's stack.  Since commit 3f4e5e8c3d
(cmState: Return end snapshot for GetBuildsystemDirectoryParent.,
2015-09-01, v3.4.0-rc1~100^2~1), that depends on the `DirectoryEnd`
field in the directory's state.  However, when variable-only scopes were
added by commit 6954c8936f (cmState: Add a VariableScope snapshot type.,
2015-08-01, v3.4.0-rc1~179^2~1), we neglected to account for the
addition of that field by commit 52dbe654de (cmState: Record the end
position of each directory., 2015-08-01, v3.4.0-rc1~251^2~1).

Prior to commit 44a2f3f332 (Add new flow-control commands for variables
and policies scopes management, 2022-08-05, v3.25.0-rc1~257^2) this
problem went unnoticed because there was no way to have a variable scope
at the top of a directory's stack while processing a subdirectory. Now
the `block()/endblock()` commands enable the behavior, so fix tracking
of a variable scope as the top-most scope in a directory.

Fixes: #24138

Source/cmState.cxx

@@ -938,6 +938,7 @@ cmStateSnapshot cmState::CreateVariableScopeSnapshot(
   pos->ScopeParent = originSnapshot.Position;
   pos->SnapshotType = cmStateEnums::VariableScopeType;
   pos->Keep = false;
+  pos->BuildSystemDirectory->DirectoryEnd = pos;
   pos->PolicyScope = originSnapshot.Position->Policies;
   assert(originSnapshot.Position->Vars.IsValid());
 

Tests/RunCMake/block/Scope-POLICIES.cmake

@@ -2,6 +2,9 @@
 set(VAR1 "OUTER1")
 set(VAR2 "OUTER2")
 
+set(VARSUB1 "OUTERSUB1")
+set(VARSUB2 "OUTERSUB2")
+
 cmake_policy(SET CMP0139 NEW)
 
 # create a block with a new scope for policies
@@ -9,6 +12,7 @@ block(SCOPE_FOR POLICIES)
   set(VAR1 "INNER1")
   unset(VAR2)
   set(VAR3 "INNER3")
+  add_subdirectory(Scope)
 
   cmake_policy(SET CMP0139 OLD)
 endblock()
@@ -23,6 +27,12 @@ endif()
 if(NOT DEFINED VAR3 OR NOT VAR3 STREQUAL "INNER3")
   message(SEND_ERROR "block/endblock: VAR3 has unexpected value: ${VAR3}")
 endif()
+if(NOT DEFINED VARSUB1 OR NOT VARSUB1 STREQUAL "SUBDIR1")
+  message(SEND_ERROR "block/endblock: VARSUB1 has unexpected value: ${VARSUB1}")
+endif()
+if(NOT DEFINED VARSUB2 OR NOT VARSUB2 STREQUAL "SUBDIR2")
+  message(SEND_ERROR "block/endblock: VARSUB2 has unexpected value: ${VARSUB2}")
+endif()
 
 cmake_policy(GET CMP0139 CMP0139_STATUS)
 if(NOT CMP0139_STATUS STREQUAL "NEW")

Tests/RunCMake/block/Scope-VARIABLES.cmake

@@ -8,16 +8,20 @@ set(VAR5 "OUTER5")
 set(VAR6 "CACHE6" CACHE STRING "")
 set(VAR6 "OUTER6")
 
+set(VARSUB1 "OUTERSUB1")
+set(VARSUB2 "OUTERSUB2")
+
 cmake_policy(SET CMP0139 NEW)
 
 # create a block with a new scope for variables
-block(SCOPE_FOR VARIABLES PROPAGATE VAR3 VAR4 VAR5 VAR6 VAR7)
+block(SCOPE_FOR VARIABLES PROPAGATE VAR3 VAR4 VAR5 VAR6 VAR7 VARSUB2)
   set(VAR1 "INNER1")
   set(VAR2 "INNER2" PARENT_SCOPE)
   set(VAR3 "INNER3")
   unset(VAR4)
   unset(VAR6)
   set(VAR7 "INNER7")
+  add_subdirectory(Scope)
 
   cmake_policy(SET CMP0139 OLD)
 endblock()
@@ -45,6 +49,12 @@ endif()
 if(NOT DEFINED VAR7 OR NOT VAR7 STREQUAL "INNER7")
   message(SEND_ERROR "block/endblock: VAR7 has unexpected value: ${VAR7}")
 endif()
+if(NOT DEFINED VARSUB1 OR NOT VARSUB1 STREQUAL "OUTERSUB1")
+  message(SEND_ERROR "block/endblock: VARSUB1 has unexpected value: ${VARSUB1}")
+endif()
+if(NOT DEFINED VARSUB2 OR NOT VARSUB2 STREQUAL "SUBDIR2")
+  message(SEND_ERROR "block/endblock: VARSUB2 has unexpected value: ${VARSUB2}")
+endif()
 
 cmake_policy(GET CMP0139 CMP0139_STATUS)
 if(NOT CMP0139_STATUS STREQUAL "OLD")

Tests/RunCMake/block/Scope.cmake

@@ -8,16 +8,20 @@ set(VAR5 "OUTER5")
 set(VAR6 "CACHE6" CACHE STRING "")
 set(VAR6 "OUTER6")
 
+set(VARSUB1 "OUTERSUB1")
+set(VARSUB2 "OUTERSUB2")
+
 cmake_policy(SET CMP0139 NEW)
 
 # create a block with a new scope for variables and policies
-block(PROPAGATE VAR3 VAR4 VAR5 VAR6 VAR7)
+block(PROPAGATE VAR3 VAR4 VAR5 VAR6 VAR7 VARSUB2)
   set(VAR1 "INNER1")
   set(VAR2 "INNER2" PARENT_SCOPE)
   set(VAR3 "INNER3")
   unset(VAR4)
   unset(VAR6)
   set(VAR7 "INNER7")
+  add_subdirectory(Scope)
 
   cmake_policy(SET CMP0139 OLD)
 endblock()
@@ -45,6 +49,12 @@ endif()
 if(NOT DEFINED VAR7 OR NOT VAR7 STREQUAL "INNER7")
   message(SEND_ERROR "block/endblock: VAR6 has unexpected value: ${VAR7}")
 endif()
+if(NOT DEFINED VARSUB1 OR NOT VARSUB1 STREQUAL "OUTERSUB1")
+  message(SEND_ERROR "block/endblock: VARSUB1 has unexpected value: ${VARSUB1}")
+endif()
+if(NOT DEFINED VARSUB2 OR NOT VARSUB2 STREQUAL "SUBDIR2")
+  message(SEND_ERROR "block/endblock: VARSUB2 has unexpected value: ${VARSUB2}")
+endif()
 
 cmake_policy(GET CMP0139 CMP0139_STATUS)
 if(NOT CMP0139_STATUS STREQUAL "NEW")

Tests/RunCMake/block/Scope/CMakeLists.txt

@@ -0,0 +1,2 @@
+set(VARSUB1 "SUBDIR1" PARENT_SCOPE)
+set(VARSUB2 "SUBDIR2" PARENT_SCOPE)