fix a corner case (#53)

Author: 0g-peterzhb

node/rpc/src/kv_rpc_server/impl.rs

@@ -24,6 +24,13 @@ impl KeyValueRpcServerImpl {
         start_index: u64,
         len: u64,
     ) -> RpcResult<Option<ValueSegment>> {
+        if len == 0 {
+            return Ok(Some(ValueSegment {
+                version: pair.version,
+                data: vec![],
+                size: pair.end_index - pair.start_index,
+            }));
+        }
         if start_index > pair.end_index - pair.start_index {
             return Err(error::invalid_params(
                 "start_index",
@@ -63,6 +70,14 @@ impl KeyValueRpcServerImpl {
         start_index: u64,
         len: u64,
     ) -> RpcResult<Option<KeyValueSegment>> {
+        if len == 0 {
+            return Ok(Some(KeyValueSegment {
+                version: pair.version,
+                key: pair.key,
+                data: vec![],
+                size: pair.end_index - pair.start_index,
+            }));
+        }
         if start_index > pair.end_index - pair.start_index {
             return Err(error::invalid_params(
                 "start_index",

tests/config/cosmos-genesis.json

@@ -1,7 +1,7 @@
 {
   "app_name": "0gchaind",
   "app_version": "v0.2.0-alpha.4-892-g6b920eb40",
-  "genesis_time": "2026-02-24T15:30:05.289745Z",
+  "genesis_time": "2026-02-27T06:41:33.885477Z",
   "chain_id": "0gchaind-local",
   "initial_height": 1,
   "app_hash": null,

tests/kv_iterator_test.py

@@ -1,4 +1,5 @@
 #!/usr/bin/env python3
+import base64
 import random
 from kv_test_framework.test_framework import KVTestFramework
 from utility.kv import (
@@ -39,6 +40,13 @@ def run_test(self):
         # write empty stream
         self.write_streams()
 
+        # rpc edge case tests
+        self.test_len_zero()
+        self.test_len_one()
+        self.test_len_larger_than_value()
+        self.test_start_index_at_boundary()
+        self.test_nonexistent_key()
+
     def submit(
         self,
         version,
@@ -207,6 +215,107 @@ def write_streams(self):
             pair = self.kv_nodes[0].prev(stream_id, current_key, second_version)
         assert cnt == len(self.data.items()) - deleted
 
+        self.update_data(writes)
+
+    def _get_first_key_and_value(self):
+        """Get the first non-deleted key and its value from self.data."""
+        stream_id = to_stream_id(1)
+        for stream_id_key, value in sorted(self.data.items()):
+            sid, key = stream_id_key.split(",")
+            if sid == stream_id and value is not None:
+                return stream_id, key, value
+        raise AssertionError("no non-deleted key found")
+
+    def test_len_zero(self):
+        """len=0 should return metadata with empty data, not crash."""
+        stream_id, key, value = self._get_first_key_and_value()
+        node = self.kv_nodes[0]
+
+        # kv_getValue with len=0
+        res = node.kv_get_value(stream_id, key, 0, 0)
+        assert res is not None, "kv_getValue(len=0) returned None"
+        assert_equal(base64.b64decode(res["data"].encode("utf-8")), b"")
+        assert_equal(res["size"], len(value))
+
+        # kv_getFirst with len=0
+        res = node.kv_get_first(stream_id, 0, 0)
+        assert res is not None, "kv_getFirst(len=0) returned None"
+        assert_equal(base64.b64decode(res["data"].encode("utf-8")), b"")
+        assert res["size"] > 0
+
+        # kv_getLast with len=0
+        res = node.kv_get_last(stream_id, 0, 0)
+        assert res is not None, "kv_getLast(len=0) returned None"
+        assert_equal(base64.b64decode(res["data"].encode("utf-8")), b"")
+        assert res["size"] > 0
+
+        # kv_getNext with len=0
+        res = node.kv_get_next(stream_id, key, 0, 0)
+        assert res is not None, "kv_getNext(len=0) returned None"
+        assert_equal(base64.b64decode(res["data"].encode("utf-8")), b"")
+        assert res["size"] > 0
+
+        # kv_getPrev with len=0 (use last key so there's a prev)
+        last_pair = node.seek_to_last(stream_id)
+        res = node.kv_get_prev(stream_id, last_pair["key"], 0, 0)
+        assert res is not None, "kv_getPrev(len=0) returned None"
+        assert_equal(base64.b64decode(res["data"].encode("utf-8")), b"")
+        assert res["size"] > 0
+
+    def test_len_one(self):
+        """len=1 should return exactly 1 byte of data."""
+        stream_id, key, value = self._get_first_key_and_value()
+        node = self.kv_nodes[0]
+
+        res = node.kv_get_value(stream_id, key, 0, 1)
+        assert res is not None
+        data = base64.b64decode(res["data"].encode("utf-8"))
+        assert_equal(len(data), 1)
+        assert_equal(data, value[:1])
+        assert_equal(res["size"], len(value))
+
+        res = node.kv_get_first(stream_id, 0, 1)
+        assert res is not None
+        data = base64.b64decode(res["data"].encode("utf-8"))
+        assert_equal(len(data), 1)
+
+    def test_len_larger_than_value(self):
+        """len larger than remaining bytes should return clamped data."""
+        stream_id, key, value = self._get_first_key_and_value()
+        node = self.kv_nodes[0]
+
+        # read from midpoint with len larger than remaining bytes
+        mid = len(value) // 2
+        remaining = len(value) - mid
+        oversized_len = remaining + 1024
+        res = node.kv_get_value(stream_id, key, mid, oversized_len)
+        assert res is not None
+        data = base64.b64decode(res["data"].encode("utf-8"))
+        assert_equal(data, value[mid:])
+        assert_equal(res["size"], len(value))
+
+    def test_start_index_at_boundary(self):
+        """start_index at or past value size should return error."""
+        stream_id, key, value = self._get_first_key_and_value()
+        node = self.kv_nodes[0]
+
+        try:
+            node.kv_get_value(stream_id, key, len(value) + 1, 1)
+            assert False, "expected error for start_index past value size"
+        except Exception:
+            pass
+
+    def test_nonexistent_key(self):
+        """Querying a key that doesn't exist should return empty."""
+        stream_id = to_stream_id(1)
+        node = self.kv_nodes[0]
+        fake_key = "ff" * 32  # key that was never written
+
+        res = node.kv_get_value(stream_id, fake_key, 0, 1)
+        assert res is not None
+        assert_equal(base64.b64decode(res["data"].encode("utf-8")), b"")
+        assert_equal(res["size"], 0)
+
 
 if __name__ == "__main__":
     KVPutGetTest().main()