logging: don't pick up later mutations

mitmproxy/log.py

@@ -6,7 +6,9 @@ from mitmproxy import hooks
 
 class LogEntry:
     def __init__(self, msg, level):
-        self.msg = msg
+        # it's important that we serialize to string here already so that we don't pick up changes
+        # happening after this log statement.
+        self.msg = str(msg)
         self.level = level
 
     def __eq__(self, other):

test/mitmproxy/test_log.py

@@ -9,3 +9,10 @@ def test_logentry():
     assert e == e
     assert e != f
     assert e != 42
+
+
+def test_dont_pick_up_mutations():
+    x = {"foo": "bar"}
+    e = log.LogEntry(x, "info")
+    x["foo"] = "baz"  # this should not affect the log entry anymore.
+    assert repr(e) == "LogEntry({'foo': 'bar'}, info)"