🐛 fix(core): return JSON-RPC protocol errors

lsp-server/test/test_core_server.py

@@ -14,6 +14,10 @@ def frame(message: dict) -> bytes:
     return f"Content-Length: {len(body)}\r\n\r\n".encode("ascii") + body
 
 
+def raw_frame(body: bytes) -> bytes:
+    return f"Content-Length: {len(body)}\r\n\r\n".encode("ascii") + body
+
+
 def read_messages(data: bytes) -> list[dict]:
     messages = []
     offset = 0
@@ -169,12 +173,48 @@ def assert_lifecycle(server: Path) -> None:
         client.kill()
 
 
+def assert_json_rpc_errors(server: Path) -> None:
+    payload = b"".join([
+        raw_frame(b'{"jsonrpc":"2.0",'),
+        raw_frame(b"[]"),
+        raw_frame(b'{"jsonrpc":"1.0","id":7,"method":"initialize"}'),
+        frame({
+            "jsonrpc": "2.0",
+            "id": 8,
+            "method": "initialize",
+            "params": {},
+        }),
+        frame({"jsonrpc": "2.0", "id": 9, "method": "missing/method"}),
+        frame({"jsonrpc": "2.0", "id": 10, "method": "shutdown"}),
+        frame({"jsonrpc": "2.0", "method": "exit"}),
+    ])
+    result = run_raw(server, payload)
+    if result.returncode != 0:
+        raise RuntimeError("JSON-RPC error sequence should shut down cleanly")
+
+    responses = read_messages(result.stdout)
+    if responses[0].get("id", "missing") is not None:
+        raise RuntimeError(
+            f"ParseError response should use a null id: {responses[0]!r}")
+    if responses[0].get("error", {}).get("code") != -32700:
+        raise RuntimeError("Malformed JSON should return ParseError")
+    if responses[1].get("id", "missing") is not None:
+        raise RuntimeError("InvalidRequest response should use a null id")
+    if responses[1].get("error", {}).get("code") != -32600:
+        raise RuntimeError("A non-object JSON value should return InvalidRequest")
+    if response_by_id(result.stdout, 7).get("error", {}).get("code") != -32600:
+        raise RuntimeError("jsonrpc other than 2.0 should return InvalidRequest")
+    if response_by_id(result.stdout, 9).get("error", {}).get("code") != -32601:
+        raise RuntimeError("Unknown request method should return MethodNotFound")
+
+
 def main() -> int:
     parser = argparse.ArgumentParser()
     parser.add_argument("--server", type=Path, required=True)
     args = parser.parse_args()
 
     assert_lifecycle(args.server)
+    assert_json_rpc_errors(args.server)
     return 0