Exclude non-primitive values from memoization

2 files changed, 17 insertions, 0 deletions

diff --git a/src/engine/SCons/Node/Python.py b/src/engine/SCons/Node/Python.py
index 7b25edb..1fb2866 100644
--- a/src/engine/SCons/Node/Python.py
+++ b/src/engine/SCons/Node/Python.py
@@ -184,6 +184,11 @@ def ValueWithMemo(value, built_value=None):
     if built_value:
         return Value(value, built_value)
 
+    # No current support for memoizing non-primitive types in case they change
+    # after this call.
+    if not isinstance(value, (int, str, float, bool)):
+        return Value(value, built_value)
+
     value_str = str(value)
     if value_str in _memoLookupMap:
         return _memoLookupMap[value_str]
diff --git a/src/engine/SCons/Node/PythonTests.py b/src/engine/SCons/Node/PythonTests.py
index e1aa58b..6af3e60 100644
--- a/src/engine/SCons/Node/PythonTests.py
+++ b/src/engine/SCons/Node/PythonTests.py
@@ -132,6 +132,18 @@ class ValueMemoTestCase(unittest.TestCase):
         v2 = SCons.Node.Python.Value('c', 'ca')
         assert v1 is not v2
 
+    def test_non_primitive_values(self):
+        """Confirm that non-primitive values are not memoized."""
+        d = {'a': 1}
+        v1 = SCons.Node.Python.Value(d)
+        v2 = SCons.Node.Python.Value(d)
+        assert v1 is not v2
+
+        l = [1]
+        v3 = SCons.Node.Python.Value(l)
+        v4 = SCons.Node.Python.Value(l)
+        assert v3 is not v4
+
 if __name__ == "__main__":
     unittest.main()