Add config option to specify json float serialization precision

server/config.py

@@ -124,6 +124,8 @@ def __init__(self):
         self.QUEUE_POP_DESIRED_MATCHES = 2.5
         # How many previous queue sizes to consider
         self.QUEUE_POP_TIME_MOVING_AVG_SIZE = 5
+        # The number of decimal places to use for float serialization
+        self.JSON_FLOAT_DIGITS_PRECISION = 2
 
         self._defaults = {
             key: value for key, value in vars(self).items() if key.isupper()

server/protocol/protocol.py

@@ -2,12 +2,32 @@
 import json
 from abc import ABCMeta, abstractmethod
 from asyncio import StreamReader, StreamWriter
+from typing import Iterable, Mapping
 
 import server.metrics as metrics
+from server.config import config
 
 from ..asyncio_extensions import synchronizedmethod
 
-json_encoder = json.JSONEncoder(separators=(",", ":"))
+
+class CustomJSONEncoder(json.JSONEncoder):
+    # taken from https://stackoverflow.com/a/60243503
+    def encode(self, obj):
+        if isinstance(obj, Mapping):
+            dict_content = ", ".join(
+                f"{self.encode(key)}: {self.encode(value)}"
+                for (key, value) in obj.items()
+            )
+            return '{' + dict_content + '}'
+        elif isinstance(obj, Iterable) and not isinstance(obj, str):
+            return "[" + ", ".join(map(self.encode, obj)) + "]"
+        elif isinstance(obj, float):
+            return f"{obj:.{config.JSON_FLOAT_DIGITS_PRECISION}f}"
+        else:
+            return super().encode(obj)
+
+
+json_encoder = CustomJSONEncoder(separators=(",", ":"))
 
 
 class DisconnectedError(ConnectionError):

tests/unit_tests/test_protocol.py

@@ -1,4 +1,5 @@
 import asyncio
+import copy
 import json
 import struct
 from contextlib import asynccontextmanager, closing
@@ -8,11 +9,13 @@
 from hypothesis import example, given, settings
 from hypothesis import strategies as st
 
+from server.config import config
 from server.protocol import (
     DisconnectedError,
     QDataStreamProtocol,
     SimpleJsonProtocol
 )
+from server.protocol.protocol import json_encoder
 
 
 @pytest.fixture(scope="session")
@@ -256,3 +259,54 @@ async def test_read_when_disconnected(protocol):
 
     with pytest.raises(DisconnectedError):
         await protocol.read_message()
+
+
+def test_json_encoder_float_serialization():
+    assert json_encoder.encode(123.0) == '123.00'
+    assert json_encoder.encode(0.99) == '0.99'
+    assert json_encoder.encode(0.999) == '1.00'
+    assert json_encoder.encode('simple words') == '"simple words"'
+    assert json_encoder.encode([1, 2, 3]) == '[1, 2, 3]'
+    assert json_encoder.encode({'a': 1}) == '{"a": 1}'
+
+    # Check that we did not brake the original behaviour of other things
+    delta_ladder, delta_tmm = 200.3654233558, 19.879223123
+
+    info_dict = {
+        "command": "matchmaker_info",
+        "queues": [
+            {
+                "queue_name": "ladder1v1",
+                "queue_pop_time": "2002-01-01T23:59:59.595959",
+                "queue_pop_time_delta": delta_ladder,
+                "num_players": 3,
+                "boundary_80s": [(1200, 1600), (1600, 2000), (300, 700)],
+                "boundary_75s": [(1300, 1500), (1700, 1900), (400, 600)],
+                "team_size": 1,
+            },
+            {
+                "queue_name": "tmm2v2",
+                "queue_pop_time": "2002-01-01T23:56:23.234255",
+                "queue_pop_time_delta": delta_tmm,
+                "num_players": 4,
+                "boundary_80s": [
+                    (1200, 1600), (1600, 2000), (300, 700), (300, 700),
+                ],
+                "boundary_75s": [
+                    (1300, 1500), (1700, 1900), (400, 600), (400, 600),
+                ],
+                "team_size": 2,
+            },
+        ]
+    }
+
+    expected_info_dict = copy.deepcopy(info_dict)
+
+    for queue in expected_info_dict["queues"]:
+        queue["queue_pop_time_delta"] = round(
+            queue["queue_pop_time_delta"], config.JSON_FLOAT_DIGITS_PRECISION,
+        )
+
+    assert json_encoder.encode(info_dict) == (
+        json.JSONEncoder().encode(expected_info_dict)
+    )