make option redeclaration silent if signature is the same

mitmproxy/addonmanager.py

@@ -86,7 +86,18 @@ class Loader:
         choices: typing.Optional[typing.Sequence[str]] = None
     ) -> None:
         if name in self.master.options:
-            ctx.log.warn("Over-riding existing option %s" % name)
+            existing = self.master.options._options[name]
+            same_signature = (
+                existing.name == name and
+                existing.typespec == typespec and
+                existing.default == default and
+                existing.help == help and
+                existing.choices == choices
+            )
+            if same_signature:
+                return
+            else:
+                ctx.log.warn("Over-riding existing option %s" % name)
         self.master.options.add_option(
             name,
             typespec,

test/mitmproxy/test_addonmanager.py

@@ -91,7 +91,15 @@ def test_loader():
     with taddons.context() as tctx:
         l = addonmanager.Loader(tctx.master)
         l.add_option("custom_option", bool, False, "help")
+        assert "custom_option" in l.master.options
+
+        # calling this again with the same signature is a no-op.
         l.add_option("custom_option", bool, False, "help")
+        assert not tctx.master.has_log("Over-riding existing option")
+
+        # a different signature should emit a warning though.
+        l.add_option("custom_option", bool, True, "help")
+        assert tctx.master.has_log("Over-riding existing option")
 
         def cmd(a: str) -> str:
             return "foo"