Handle None in the formatting middleware

newsfragments/2546.bugfix.rst

@@ -0,0 +1 @@
+Handle `None` in the formatting middleware

tests/core/middleware/test_formatting_middleware.py

@@ -0,0 +1,126 @@
+import pytest
+from unittest.mock import (
+    Mock,
+)
+
+from web3 import (
+    Web3,
+)
+from web3.middleware import (
+    construct_error_generator_middleware,
+    construct_formatting_middleware,
+    construct_result_generator_middleware,
+)
+from web3.providers.base import (
+    BaseProvider,
+)
+from web3.types import (
+    RPCEndpoint,
+)
+
+
+class DummyProvider(BaseProvider):
+    def make_request(self, method, params):
+        raise NotImplementedError(f"Cannot make request for {method}:{params}")
+
+
+@pytest.fixture
+def w3():
+    return Web3(provider=DummyProvider(), middlewares=[])
+
+
+def test_formatting_middleware(w3):
+    # No formatters by default
+    w3.middleware_onion.add(construct_formatting_middleware())
+    w3.middleware_onion.add(
+        construct_result_generator_middleware(
+            {
+                "test_endpoint": lambda method, params: "done",
+            }
+        )
+    )
+
+    expected = "done"
+    actual = w3.manager.request_blocking("test_endpoint", [])
+    assert actual == expected
+
+
+def test_formatting_middleware_no_method(w3):
+    w3.middleware_onion.add(construct_formatting_middleware())
+
+    # Formatting middleware requires an endpoint
+    with pytest.raises(NotImplementedError):
+        w3.manager.request_blocking("test_endpoint", [])
+
+
+def test_formatting_middleware_request_formatters(w3):
+    callable_mock = Mock()
+    w3.middleware_onion.add(
+        construct_result_generator_middleware(
+            {RPCEndpoint("test_endpoint"): lambda method, params: "done"}
+        )
+    )
+
+    w3.middleware_onion.add(
+        construct_formatting_middleware(
+            request_formatters={RPCEndpoint("test_endpoint"): callable_mock}
+        )
+    )
+
+    expected = "done"
+    actual = w3.manager.request_blocking("test_endpoint", ["param1"])
+
+    callable_mock.assert_called_once_with(["param1"])
+    assert actual == expected
+
+
+def test_formatting_middleware_result_formatters(w3):
+    w3.middleware_onion.add(
+        construct_result_generator_middleware(
+            {RPCEndpoint("test_endpoint"): lambda method, params: "done"}
+        )
+    )
+    w3.middleware_onion.add(
+        construct_formatting_middleware(
+            result_formatters={RPCEndpoint("test_endpoint"): lambda x: f"STATUS:{x}"}
+        )
+    )
+
+    expected = "STATUS:done"
+    actual = w3.manager.request_blocking("test_endpoint", [])
+    assert actual == expected
+
+
+def test_formatting_middleware_result_formatters_for_none(w3):
+    w3.middleware_onion.add(
+        construct_result_generator_middleware(
+            {RPCEndpoint("test_endpoint"): lambda method, params: None}
+        )
+    )
+    w3.middleware_onion.add(
+        construct_formatting_middleware(
+            result_formatters={RPCEndpoint("test_endpoint"): lambda x: hex(x)}
+        )
+    )
+
+    expected = None
+    actual = w3.manager.request_blocking("test_endpoint", [])
+    assert actual == expected
+
+
+def test_formatting_middleware_error_formatters(w3):
+    w3.middleware_onion.add(
+        construct_error_generator_middleware(
+            {RPCEndpoint("test_endpoint"): lambda method, params: "error"}
+        )
+    )
+    w3.middleware_onion.add(
+        construct_formatting_middleware(
+            result_formatters={RPCEndpoint("test_endpoint"): lambda x: f"STATUS:{x}"}
+        )
+    )
+
+    expected = "error"
+    with pytest.raises(ValueError) as err:
+        w3.manager.request_blocking("test_endpoint", [])
+    assert str(err.value) == expected

web3/middleware/formatting.py

@@ -50,7 +50,11 @@ def _format_response(
             response, response_type, method_response_formatter(appropriate_response)
         )
 
-    if "result" in response and method in result_formatters:
+    if (
+        "result" in response
+        and response["result"] is not None
+        and method in result_formatters
+    ):
         return _format_response("result", result_formatters[method])
     elif "error" in response and method in error_formatters:
         return _format_response("error", error_formatters[method])