Preserve empty method names

CHANGELOG.md

@@ -148,6 +148,8 @@ work in 5.x but give a `DeprecationWarning`, and will be removed in 6.0.
 
 ### Fixes
 
+- `@method(name="")` now registers the empty name. It used to ignore that
+  name and register the function's name instead.
 - The development server, `serve()`, dropped every connection without a
   response when `sys.stderr` was `None`. That's the case in a PyInstaller app
   built with `--noconsole` (#269). It now logs requests through the logging

jsonrpcserver/methods.py

@@ -78,7 +78,7 @@ def add(a: int, b: int) -> Result:
     """
 
     def decorator(func: F) -> F:
-        method_name = name or func.__name__
+        method_name = func.__name__ if name is None else name
         if method_name.startswith("rpc."):
             warnings.warn(
                 f"Method names starting with 'rpc.' are reserved by the JSON-RPC spec "

tests/test_methods.py

@@ -1,5 +1,8 @@
 """Test methods.py"""
 
+import pytest
+
+from jsonrpcserver import Result, Success, dispatch
 from jsonrpcserver.methods import global_methods, method
 
 # pylint: disable=missing-function-docstring
@@ -19,3 +22,16 @@ def name() -> None:
         pass
 
     assert callable(global_methods["new_name"])
+
+
+def test_decorator_empty_name(monkeypatch: pytest.MonkeyPatch) -> None:
+    monkeypatch.setitem(global_methods, "", lambda: Success("previous"))
+
+    @method(name="")
+    def empty_name() -> Result:
+        return Success("pong")
+
+    assert dispatch('{"jsonrpc": "2.0", "method": "", "id": 1}') == (
+        '{"jsonrpc": "2.0", "result": "pong", "id": 1}'
+    )
+    assert global_methods[""] is empty_name