doc: add comments and release-notes for JSON-RPC 2.0

doc/JSON-RPC-interface.md

@@ -74,6 +74,22 @@ major version via the `-deprecatedrpc=` command line option. The release notes
 of a new major release come with detailed instructions on what RPC features
 were deprecated and how to re-enable them temporarily.
 
+## JSON-RPC 1.1 vs 2.0
+
+The server recognizes [JSON-RPC v2.0](https://www.jsonrpc.org/specification) requests
+and responds accordingly. A 2.0 request is identified by the presence of
+`"jsonrpc": "2.0"` in the request body. If that key + value is not present in a request,
+the legacy JSON-RPC v1.1 protocol is followed instead, which was the only available
+protocol in previous releases.
+
+|| 1.1 | 2.0 |
+|-|-|-|
+| Request marker | `"version": "1.1"` (or none) | `"jsonrpc": "2.0"` |
+| Response marker | (none) | `"jsonrpc": "2.0"` |
+| `"error"` and `"result"` fields in response | both present | only one is present |
+| HTTP codes in response | `200` unless there is any kind of RPC error (invalid parameters, method not found, etc) | Always `200` unless there is an actual HTTP server error (request parsing error, endpoint not found, etc) |
+| Notifications: requests that get no reply | (not supported) | Supported for requests that exclude the "id" field |
+
 ## Security
 
 The RPC interface allows other programs to control Bitcoin Core,

doc/release-notes-27101.md

@@ -0,0 +1,9 @@
+JSON-RPC
+--------
+
+The JSON-RPC server now recognizes JSON-RPC 2.0 requests and responds with
+strict adherence to the specification (https://www.jsonrpc.org/specification):
+
+- Returning HTTP "204 No Content" responses to JSON-RPC 2.0 notifications instead of full responses.
+- Returning HTTP "200 OK" responses in all other cases, rather than 404 responses for unknown methods, 500 responses for invalid parameters, etc.
+- Returning either "result" fields or "error" fields in JSON-RPC responses, rather than returning both fields with one field set to null.

src/rpc/request.cpp

@@ -26,6 +26,17 @@
  *
  * 1.0 spec: http://json-rpc.org/wiki/specification
  * 1.2 spec: http://jsonrpc.org/historical/json-rpc-over-http.html
+ *
+ * If the server receives a request with the JSON-RPC 2.0 marker `{"jsonrpc": "2.0"}`
+ * then Bitcoin will respond with a strictly specified response.
+ * It will only return an HTTP error code if an actual HTTP error is encountered
+ * such as the endpoint is not found (404) or the request is not formatted correctly (500).
+ * Otherwise the HTTP code is always OK (200) and RPC errors will be included in the
+ * response body.
+ *
+ * 2.0 spec: https://www.jsonrpc.org/specification
+ *
+ * Also see http://www.simple-is-better.org/rpc/#differences-between-1-0-and-2-0
  */
 
 UniValue JSONRPCRequestObj(const std::string& strMethod, const UniValue& params, const UniValue& id)

src/rpc/util.cpp

@@ -161,7 +161,7 @@ std::string HelpExampleCliNamed(const std::string& methodname, const RPCArgList&
 
 std::string HelpExampleRpc(const std::string& methodname, const std::string& args)
 {
-    return "> curl --user myusername --data-binary '{\"jsonrpc\": \"1.0\", \"id\": \"curltest\", "
+    return "> curl --user myusername --data-binary '{\"jsonrpc\": \"2.0\", \"id\": \"curltest\", "
         "\"method\": \"" + methodname + "\", \"params\": [" + args + "]}' -H 'content-type: text/plain;' http://127.0.0.1:8332/\n";
 }
 
@@ -172,7 +172,7 @@ std::string HelpExampleRpcNamed(const std::string& methodname, const RPCArgList&
         params.pushKV(param.first, param.second);
     }
 
-    return "> curl --user myusername --data-binary '{\"jsonrpc\": \"1.0\", \"id\": \"curltest\", "
+    return "> curl --user myusername --data-binary '{\"jsonrpc\": \"2.0\", \"id\": \"curltest\", "
            "\"method\": \"" + methodname + "\", \"params\": " + params.write() + "}' -H 'content-type: text/plain;' http://127.0.0.1:8332/\n";
 }
 

src/test/rpc_tests.cpp

@@ -551,7 +551,7 @@ BOOST_AUTO_TEST_CASE(help_example)
     // test different argument types
     const RPCArgList& args = {{"foo", "bar"}, {"b", true}, {"n", 1}};
     BOOST_CHECK_EQUAL(HelpExampleCliNamed("test", args), "> bitcoin-cli -named test foo=bar b=true n=1\n");
-    BOOST_CHECK_EQUAL(HelpExampleRpcNamed("test", args), "> curl --user myusername --data-binary '{\"jsonrpc\": \"1.0\", \"id\": \"curltest\", \"method\": \"test\", \"params\": {\"foo\":\"bar\",\"b\":true,\"n\":1}}' -H 'content-type: text/plain;' http://127.0.0.1:8332/\n");
+    BOOST_CHECK_EQUAL(HelpExampleRpcNamed("test", args), "> curl --user myusername --data-binary '{\"jsonrpc\": \"2.0\", \"id\": \"curltest\", \"method\": \"test\", \"params\": {\"foo\":\"bar\",\"b\":true,\"n\":1}}' -H 'content-type: text/plain;' http://127.0.0.1:8332/\n");
 
     // test shell escape
     BOOST_CHECK_EQUAL(HelpExampleCliNamed("test", {{"foo", "b'ar"}}), "> bitcoin-cli -named test foo='b'''ar'\n");
@@ -564,7 +564,7 @@ BOOST_AUTO_TEST_CASE(help_example)
     obj_value.pushKV("b", false);
     obj_value.pushKV("n", 1);
     BOOST_CHECK_EQUAL(HelpExampleCliNamed("test", {{"name", obj_value}}), "> bitcoin-cli -named test name='{\"foo\":\"bar\",\"b\":false,\"n\":1}'\n");
-    BOOST_CHECK_EQUAL(HelpExampleRpcNamed("test", {{"name", obj_value}}), "> curl --user myusername --data-binary '{\"jsonrpc\": \"1.0\", \"id\": \"curltest\", \"method\": \"test\", \"params\": {\"name\":{\"foo\":\"bar\",\"b\":false,\"n\":1}}}' -H 'content-type: text/plain;' http://127.0.0.1:8332/\n");
+    BOOST_CHECK_EQUAL(HelpExampleRpcNamed("test", {{"name", obj_value}}), "> curl --user myusername --data-binary '{\"jsonrpc\": \"2.0\", \"id\": \"curltest\", \"method\": \"test\", \"params\": {\"name\":{\"foo\":\"bar\",\"b\":false,\"n\":1}}}' -H 'content-type: text/plain;' http://127.0.0.1:8332/\n");
 
     // test array params
     UniValue arr_value(UniValue::VARR);
@@ -572,7 +572,7 @@ BOOST_AUTO_TEST_CASE(help_example)
     arr_value.push_back(false);
     arr_value.push_back(1);
     BOOST_CHECK_EQUAL(HelpExampleCliNamed("test", {{"name", arr_value}}), "> bitcoin-cli -named test name='[\"bar\",false,1]'\n");
-    BOOST_CHECK_EQUAL(HelpExampleRpcNamed("test", {{"name", arr_value}}), "> curl --user myusername --data-binary '{\"jsonrpc\": \"1.0\", \"id\": \"curltest\", \"method\": \"test\", \"params\": {\"name\":[\"bar\",false,1]}}' -H 'content-type: text/plain;' http://127.0.0.1:8332/\n");
+    BOOST_CHECK_EQUAL(HelpExampleRpcNamed("test", {{"name", arr_value}}), "> curl --user myusername --data-binary '{\"jsonrpc\": \"2.0\", \"id\": \"curltest\", \"method\": \"test\", \"params\": {\"name\":[\"bar\",false,1]}}' -H 'content-type: text/plain;' http://127.0.0.1:8332/\n");
 
     // test types don't matter for shell
     BOOST_CHECK_EQUAL(HelpExampleCliNamed("foo", {{"arg", true}}), HelpExampleCliNamed("foo", {{"arg", "true"}}));