Use default opset only if functions don't use opset (#1564)

Fix bug reported in Issue #1559 : look at opsets imported by functions
_before_ using a default.

onnxscript/converter_test.py

@@ -675,6 +675,24 @@ def sum(n: INT64) -> INT64:
         self.check_run(sum, [np.array(5, dtype=np.int64)], np.array(10, dtype=np.int64))
         self.check_run(sum, [np.array(-5, dtype=np.int64)], np.array(0, dtype=np.int64))
 
+    def test_function_opset_import(self):
+        """Test that model inherits opset version from the function."""
+        from onnxscript import opset19
+
+        @script()
+        def double(x):
+            return opset19.Add(x, x)
+
+        @script()
+        def model(x):
+            return double(x)
+
+        model_proto = model.to_model_proto()
+        onnx_opset_import = [opset for opset in model_proto.opset_import if opset.domain == ""]
+
+        self.assertEqual(len(onnx_opset_import), 1)
+        self.assertEqual(onnx_opset_import[0].version, 19)
+
 
 if __name__ == "__main__":
     unittest.main(verbosity=2)

onnxscript/irbuilder.py

@@ -370,13 +370,19 @@ def to_proto(f):
         for n in self.stmts:
             if n.callee.opset.domain not in opsets:
                 opsets[n.callee.opset.domain] = n.callee.opset.version
+
+        for proto in functions:
+            if proto.domain not in opsets:
+                opsets[proto.domain] = 1
+            # TODO(rama): Handle conflicts with appropriate error/warning message.
+            for opset in proto.opset_import:
+                if opset.domain not in opsets:
+                    opsets[opset.domain] = opset.version
+
         if "" not in opsets:
             # No operator is using the standard opset.
             # A default value is given.
             opsets[""] = onnx_opset_version()
-        for proto in functions:
-            if proto.domain not in opsets:
-                opsets[proto.domain] = 1
 
         if "ir_version" not in kwargs:
             kwargs["ir_version"] = select_ir_version(opsets[""])