be consistant when handling null props, remove them all

lang/funcs/collection.go

@@ -192,6 +192,12 @@ func recursiveMerge(newValue cty.Value, existingValue cty.Value) cty.Value {
 
 		mergedMap[key] = recursiveMerge(newValue, mergedMap[key])
 	}
+	// strip out any null properties
+	for key, value := range mergedMap {
+		if value.IsNull() {
+			delete(mergedMap, key)
+		}
+	}
 
 	return wrapAsObjectOrMap(mergedMap)
 }

lang/funcs/collection_test.go

@@ -14,6 +14,27 @@ func TestDeepMerge(t *testing.T) {
 		Want   cty.Value
 		Err    bool
 	}{
+		{ // remove props if set to null
+			[]cty.Value{
+				cty.MapVal(map[string]cty.Value{
+					"a": cty.StringVal("a"),
+					"b": cty.StringVal("b"),
+					"c": cty.NullVal(cty.String),
+					"d": cty.StringVal("d"),
+				}),
+				cty.MapVal(map[string]cty.Value{
+					"b": cty.NullVal(cty.String),
+					"c": cty.StringVal("c"),
+					"e": cty.NullVal(cty.String),
+				}),
+			},
+			cty.MapVal(map[string]cty.Value{
+				"a": cty.StringVal("a"),
+				"c": cty.StringVal("c"),
+				"d": cty.StringVal("d"),
+			}),
+			false,
+		},
 		{
 			[]cty.Value{
 				cty.ObjectVal(map[string]cty.Value{

website/docs/configuration/functions/deepmerge.html.md

@@ -23,6 +23,10 @@ or object that contains a merged set of elements from all arguments.
 The behavior is exactly the same as `merge`, but it will recurse in to objects, and supports
 partial updates of nested objects.
 
+## Null Values
+Any properties that are set to a `null` value will be removed from the final object/map. If you wish
+to keep these properties, make sure to fill them with a default value (ex: `{}`)
+
 ## Examples
 
 ```