Pass through kwargs to json.loads call in JsonParser (#518)

Summary:
Pull Request resolved: #518

The comment of this class suggests the keyword arguments in the constructor will be passed through to the json.loads call. However, `self.kwargs` is not actually passed through to the call.

Updated the example in the README too

Reviewed By: ejguan

Differential Revision: D37162608

fbshipit-source-id: b73a6cfc58befbfabfef3595d9b00cef78852273

README.md

@@ -148,7 +148,7 @@ class JsonParserIterDataPipe(IterDataPipe):
     def __iter__(self):
         for file_name, stream in self.source_datapipe:
             data = stream.read()
-            yield file_name, json.loads(data)
+            yield file_name, json.loads(data, **self.kwargs)
 
     def __len__(self):
         return len(self.source_datapipe)

test/test_local_io.py

@@ -309,6 +309,14 @@ def is_nonempty_json(path_and_stream):
         with self.assertRaisesRegex(TypeError, "len"):
             len(json_dp)
 
+        # kwargs Test:
+        json_dp = JsonParser(datapipe_nonempty, parse_int=str)
+        expected_res = [
+            ("1.json", ["foo", {"bar": ["baz", None, 1.0, "2"]}]),
+            ("2.json", {"__complex__": True, "real": "1", "imag": "2"}),
+        ]
+        self.assertEqual(expected_res, list(json_dp))
+
     def test_saver_iterdatapipe(self):
         # Functional Test: Saving some data
         name_to_data = {"1.txt": b"DATA1", "2.txt": b"DATA2", "3.txt": b"DATA3"}

torchdata/datapipes/iter/util/jsonparser.py

@@ -41,7 +41,7 @@ def __iter__(self) -> Iterator[Tuple[str, Dict]]:
         for file_name, stream in self.source_datapipe:
             data = stream.read()
             stream.close()
-            yield file_name, json.loads(data)
+            yield file_name, json.loads(data, **self.kwargs)
 
     def __len__(self) -> int:
         return len(self.source_datapipe)