Merge bitcoin/bitcoin#25367: [contrib] message-capture-parser: fix out of bounds error for empty vectors

42bbbba7c83d1e2baad18b4c6f05bad1358eb117 message-capture-parser: fix out of bounds error for empty vectors (Sebastian Falbesoner)

Pull request description:

  The script [message-capture-parser.py](https://github.com/bitcoin/bitcoin/blob/master/contrib/message-capture/message-capture-parser.py) currently throws an "out of bounds" error if a message containing an empty integer vector element is tried to converted to JSON (e.g. by the BIP157 message `cfcheckpt` with empty `FilterHeaders` vector):
  ```
  Traceback (most recent call last):
    File "/home/honey/bitcoin/./contrib/message-capture/message-capture-parser.py", line 217, in <module>
      main()
    File "/home/honey/bitcoin/./contrib/message-capture/message-capture-parser.py", line 202, in main
      process_file(str(capture), messages, "recv" in capture.stem, progress_bar)
    File "/home/honey/bitcoin/./contrib/message-capture/message-capture-parser.py", line 162, in process_file
      msg_dict["body"] = to_jsonable(msg)
    File "/home/honey/bitcoin/./contrib/message-capture/message-capture-parser.py", line 85, in to_jsonable
      elif slot in HASH_INT_VECTORS and isinstance(val[0], int):
  IndexError: list index out of range
  ```

  Fix this by using the `all(...)` predicate rather to access the first element `val[0]` (which in the error case doesn't exist).

ACKs for top commit:
  laanwj:
    Code review ACK 42bbbba7c83d1e2baad18b4c6f05bad1358eb117

Tree-SHA512: 139ec6b90304a69f26ec731e6f12b216fa10e554f777505b61adfa1e569f6861a4a849159dd1eae7a1aa0427e8598af226b6f0c4015020dcac8ab109fbc35dba

1 files changed, 2 insertions, 1 deletions

diff --git a/contrib/message-capture/message-capture-parser.py b/contrib/message-capture/message-capture-parser.py
index 9988478f1b..eefd22a60e 100755
--- a/contrib/message-capture/message-capture-parser.py
+++ b/contrib/message-capture/message-capture-parser.py
@@ -79,7 +79,8 @@ def to_jsonable(obj: Any) -> Any:
             val = getattr(obj, slot, None)
             if slot in HASH_INTS and isinstance(val, int):
                 ret[slot] = ser_uint256(val).hex()
-            elif slot in HASH_INT_VECTORS and isinstance(val[0], int):
+            elif slot in HASH_INT_VECTORS:
+                assert all(isinstance(a, int) for a in val)
                 ret[slot] = [ser_uint256(a).hex() for a in val]
             else:
                 ret[slot] = to_jsonable(val)