Fix instance check for concatenated values (#354)

Fixes #353.

Author: stefanvanburen

gen/tests/example/v1/validations_pb2.py

@@ -111,3 +111,16 @@ message RepeatedEmbedSkip {
 message InvalidRESyntax {
   string value = 1 [(buf.validate.field).string.pattern = "^\\z"];
 }
+
+// via #353.
+
+message ConcatenatedValues {
+  option (buf.validate.message).cel = {
+    id: "globally_unique_names"
+    message: "all values in bar and baz must be globally unique"
+    expression: "(this.bar + this.baz).unique()"
+  };
+
+  repeated string bar = 1;
+  repeated string baz = 2;
+}

gen/tests/example/v1/validations_pb2.pyi

@@ -332,7 +332,7 @@ def cel_is_inf(val: celtypes.Value, sign: typing.Optional[celtypes.Value] = None
 
 
 def cel_unique(val: celtypes.Value) -> celpy.Result:
-    if not isinstance(val, celtypes.ListType):
+    if not isinstance(val, celtypes.ListType) and not isinstance(val, list):
         msg = "invalid argument, expected list"
         raise celpy.CELEvalError(msg)
     return celtypes.BoolType(len(val) == len(set(val)))

proto/tests/example/v1/validations.proto

@@ -179,6 +179,14 @@ def test_multiple_validations(self):
 
         self._run_invalid_tests(msg, [expected_violation1, expected_violation2])
 
+    def test_concatenated_values(self):
+        msg = validations_pb2.ConcatenatedValues(
+            bar=["a", "b", "c"],
+            baz=["d", "e", "f"],
+        )
+
+        self._run_valid_tests(msg)
+
     def test_fail_fast(self):
         """Test that fail fast correctly fails on first violation