json: fix the issue that two arrays are merged but not append in JSON_ARRAY_APPEND. (pingcap#59688)

close pingcap#59465

Author: YangKeao

pkg/expression/builtin_json.go

@@ -1208,6 +1208,10 @@ func (b *builtinJSONArrayAppendSig) appendJSONArray(res types.BinaryJSON, p stri
 		}
 	}
 
+	// wrap the new value `v` into an array explicitly, in case that the `v` is an array itself.
+	// For example, `JSON_ARRAY_APPEND('[1]', '$', JSON_ARRAY(2, 3))` should return `[1, [2, 3]]`
+	v = types.CreateBinaryJSON([]any{v})
+
 	obj = types.MergeBinaryJSON([]types.BinaryJSON{obj, v})
 	res, err = res.Modify([]types.JSONPathExpression{pathExpr}, []types.BinaryJSON{obj}, types.JSONModifySet)
 	return res, false, err

tests/integrationtest/r/expression/json.result

@@ -861,3 +861,6 @@ json_extract('{"a":"b"}', '$[last]')
 select json_set('{"a":"b"}', '$[last]', 1);
 json_set('{"a":"b"}', '$[last]', 1)
 1
+SELECT JSON_ARRAY_APPEND('[1]', '$', JSON_ARRAY(2, 3));
+JSON_ARRAY_APPEND('[1]', '$', JSON_ARRAY(2, 3))
+[1, [2, 3]]

tests/integrationtest/t/expression/json.test

@@ -564,4 +564,7 @@ select json_extract("{\"\\f\":\"\"}", "$");
 # TestJSONExtractObjectFromLast
 select json_extract('{"a":"b"}', '$[0]');
 select json_extract('{"a":"b"}', '$[last]');
-select json_set('{"a":"b"}', '$[last]', 1);
+select json_set('{"a":"b"}', '$[last]', 1);
+
+# TestIssue59465
+SELECT JSON_ARRAY_APPEND('[1]', '$', JSON_ARRAY(2, 3));