Change BaseModel.parse_file to use Config.json_loads (#1069)

fix #1067

* Making json_loads available to parse_file

* Change BaseModel.parse_file to use Config.json_loads

* Update changes/1067-kierandarcy.md

Co-Authored-By: Samuel Colvin <samcolvin@gmail.com>

* Fixed some style issues and added missing test for parse_file_as

changes/1067-kierandarcy.md

@@ -0,0 +1 @@
+Change `BaseModel.parse_file` to use `Config.json_loads`

pydantic/main.py

@@ -425,7 +425,14 @@ class BaseModel(metaclass=ModelMetaclass):
         proto: Protocol = None,
         allow_pickle: bool = False,
     ) -> 'Model':
-        obj = load_file(path, proto=proto, content_type=content_type, encoding=encoding, allow_pickle=allow_pickle)
+        obj = load_file(
+            path,
+            proto=proto,
+            content_type=content_type,
+            encoding=encoding,
+            allow_pickle=allow_pickle,
+            json_loads=cls.__config__.json_loads,
+        )
         return cls.parse_obj(obj)
 
     @classmethod

pydantic/parse.py

@@ -51,6 +51,7 @@ def load_file(
     encoding: str = 'utf8',
     proto: Protocol = None,
     allow_pickle: bool = False,
+    json_loads: Callable[[str], Any] = json.loads,
 ) -> Any:
     path = Path(path)
     b = path.read_bytes()
@@ -60,4 +61,6 @@ def load_file(
         elif path.suffix == '.pkl':
             proto = Protocol.pickle
 
-    return load_str_bytes(b, proto=proto, content_type=content_type, encoding=encoding, allow_pickle=allow_pickle)
+    return load_str_bytes(
+        b, proto=proto, content_type=content_type, encoding=encoding, allow_pickle=allow_pickle, json_loads=json_loads,
+    )

pydantic/tools.py

@@ -1,3 +1,4 @@
+import json
 from functools import lru_cache
 from pathlib import Path
 from typing import Any, Callable, Optional, Type, TypeVar, Union
@@ -42,7 +43,15 @@ def parse_file_as(
     encoding: str = 'utf8',
     proto: Protocol = None,
     allow_pickle: bool = False,
+    json_loads: Callable[[str], Any] = json.loads,
     type_name: Optional[NameFactory] = None,
 ) -> T:
-    obj = load_file(path, proto=proto, content_type=content_type, encoding=encoding, allow_pickle=allow_pickle)
+    obj = load_file(
+        path,
+        proto=proto,
+        content_type=content_type,
+        encoding=encoding,
+        allow_pickle=allow_pickle,
+        json_loads=json_loads,
+    )
     return parse_obj_as(type_, obj, type_name=type_name)

tests/test_parse.py

@@ -1,3 +1,4 @@
+import json
 import pickle
 from typing import List, Union
 
@@ -106,6 +107,24 @@ def test_file_json_no_ext(tmpdir):
     assert Model.parse_file(str(p)) == Model(a=12, b=8)
 
 
+def test_file_json_loads(tmp_path):
+    def custom_json_loads(*args, **kwargs):
+        data = json.loads(*args, **kwargs)
+        data['a'] = 99
+        return data
+
+    class Example(BaseModel):
+        a: int
+
+        class Config:
+            json_loads = custom_json_loads
+
+    p = tmp_path / 'test_json_loads.json'
+    p.write_text('{"a": 12}')
+
+    assert Example.parse_file(p) == Example(a=99)
+
+
 def test_file_pickle(tmpdir):
     p = tmpdir.join('test.pkl')
     p.write_binary(pickle.dumps(dict(a=12, b=8)))

tests/test_tools.py

@@ -1,3 +1,4 @@
+import json
 from typing import Dict, List, Mapping
 
 import pytest
@@ -76,3 +77,14 @@ def test_parse_file_as(tmp_path):
     p = tmp_path / 'test.json'
     p.write_text('{"1": "2"}')
     assert parse_file_as(Dict[int, int], p) == {1: 2}
+
+
+def test_parse_file_as_json_loads(tmp_path):
+    def custom_json_loads(*args, **kwargs):
+        data = json.loads(*args, **kwargs)
+        data[1] = 99
+        return data
+
+    p = tmp_path / 'test_json_loads.json'
+    p.write_text('{"1": "2"}')
+    assert parse_file_as(Dict[int, int], p, json_loads=custom_json_loads) == {1: 99}