Add regression tests for dataclass serialization (#3984)

test/runtest.py

@@ -187,6 +187,31 @@ CUSTOM_OBJECTS = [
     NamedTupleExample(1, 1.0, "hi", np.zeros([3, 5]), [1, 2, 3])
 ]
 
+# Test dataclasses in Python 3.7.
+if sys.version_info >= (3, 7):
+    from dataclasses import make_dataclass
+
+    DataClass0 = make_dataclass("DataClass0", [("number", int)])
+
+    CUSTOM_OBJECTS.append(DataClass0(number=3))
+
+    class CustomClass(object):
+        def __init__(self, value):
+            self.value = value
+
+    DataClass1 = make_dataclass("DataClass1", [("custom", CustomClass)])
+
+    class DataClass2(DataClass1):
+        @classmethod
+        def from_custom(cls, data):
+            custom = CustomClass(data)
+            return cls(custom)
+
+        def __reduce__(self):
+            return (self.from_custom, (self.custom.value, ))
+
+    CUSTOM_OBJECTS.append(DataClass2(custom=CustomClass(43)))
+
 BASE_OBJECTS = PRIMITIVE_OBJECTS + COMPLEX_OBJECTS + CUSTOM_OBJECTS
 
 LIST_OBJECTS = [[obj] for obj in BASE_OBJECTS]