ENH: Isolate policy changes in included scripts

Isolation of policy changes inside scripts is important for protecting
the including context.  This teaches include() and find_package() to
imply a cmake_policy(PUSH) and cmake_policy(POP) around the scripts they
load, with a NO_POLICY_SCOPE option to disable the behavior.  This also
creates CMake Policy CMP0011 to provide compatibility.  See issue #8192.

3 files changed, 42 insertions, 1 deletions

diff --git a/Tests/PolicyScope/Bar.cmake b/Tests/PolicyScope/Bar.cmake
new file mode 100644
index 0000000..cf1904c
--- /dev/null
+++ b/Tests/PolicyScope/Bar.cmake
@@ -0,0 +1,8 @@
+cmake_minimum_required(VERSION 2.6.3)
+
+# Make sure a policy set differently by our includer is now correct.
+cmake_policy(GET CMP0003 cmp)
+check(CMP0003 "NEW" "${cmp}")
+
+# Test allowing the top-level file to not have cmake_minimum_required.
+cmake_policy(SET CMP0000 OLD)
diff --git a/Tests/PolicyScope/CMakeLists.txt b/Tests/PolicyScope/CMakeLists.txt
index ccb64de..89a89ee 100644
--- a/Tests/PolicyScope/CMakeLists.txt
+++ b/Tests/PolicyScope/CMakeLists.txt
@@ -1,5 +1,5 @@
-cmake_minimum_required(VERSION 2.6.3)
 project(PolicyScope C)
+# No cmake_minimum_required(VERSION), it's in FindFoo.
 
 #-----------------------------------------------------------------------------
 # Helper function to report results.
@@ -10,6 +10,37 @@ function(check msg lhs rhs)
 endfunction(check)
 
 #-----------------------------------------------------------------------------
+# Test using a development framework that sets policies for us.
+
+# Policy CMP0011 should not be set at this point.
+cmake_policy(GET CMP0011 cmp)
+check(CMP0011 "" "${cmp}")
+
+# Put the test modules in the search path.
+list(APPEND CMAKE_MODULE_PATH ${CMAKE_CURRENT_SOURCE_DIR})
+
+# The included file should set policies for us.
+find_package(Foo)
+
+# Check policies set by the package.
+cmake_policy(GET CMP0003 cmp)
+check(CMP0003 "OLD" "${cmp}")
+cmake_policy(GET CMP0002 cmp)
+check(CMP0002 "NEW" "${cmp}")
+cmake_policy(GET CMP0011 cmp)
+check(CMP0011 "NEW" "${cmp}")
+
+# Make sure an included file cannot change policies.
+include(Bar)
+cmake_policy(GET CMP0003 cmp)
+check(CMP0003 "OLD" "${cmp}")
+
+# Allow the included file to change policies.
+include(Bar NO_POLICY_SCOPE)
+cmake_policy(GET CMP0003 cmp)
+check(CMP0003 "NEW" "${cmp}")
+
+#-----------------------------------------------------------------------------
 # Test function and macro policy recording.
 
 # Create the functions in an isolated scope in which we change policies.
diff --git a/Tests/PolicyScope/FindFoo.cmake b/Tests/PolicyScope/FindFoo.cmake
new file mode 100644
index 0000000..5b441e2
--- /dev/null
+++ b/Tests/PolicyScope/FindFoo.cmake
@@ -0,0 +1,2 @@
+cmake_minimum_required(VERSION 2.6.3)
+cmake_policy(SET CMP0003 OLD)