feat(targets): The last received Singer message is now logged when th…

…e target fails

singer_sdk/_singerlib/encoding/_base.py

@@ -38,14 +38,25 @@ class SingerMessageType(str, enum.Enum):
 class GenericSingerReader(t.Generic[T], metaclass=abc.ABCMeta):
     """Interface for all plugins reading Singer messages as strings or bytes."""
 
+    def __init__(self) -> None:
+        super().__init__()
+        self._current_message: T | None = None
+
     @t.final
     def listen(self, file_input: t.IO[T] | None = None) -> None:
         """Read from input until all messages are processed.
 
         Args:
             file_input: Readable stream of messages. Defaults to standard in.
         """
-        self._process_lines(file_input or self.default_input)
+        try:
+            self._process_lines(file_input or self.default_input)
+        except Exception:
+            logger.info(
+                "Failed while processing Singer message: %s",
+                self._current_message,
+            )
+            raise
         self._process_endofpipe()
 
     def _process_lines(self, file_input: t.IO[T]) -> t.Counter[str]:
@@ -59,6 +70,8 @@ def _process_lines(self, file_input: t.IO[T]) -> t.Counter[str]:
         """
         stats: dict[str, int] = defaultdict(int)
         for line in file_input:
+            self._current_message = line
+
             line_dict = self.deserialize_json(line)
             self._assert_line_requires(line_dict, requires={"type"})
 

tests/core/test_io.py

@@ -6,6 +6,7 @@
 import io
 import itertools
 import json
+import logging
 from contextlib import nullcontext, redirect_stdout
 from textwrap import dedent
 
@@ -83,6 +84,29 @@ def test_listen_unknown_message():
         reader.listen(input_lines)
 
 
+def test_listen_error(caplog: pytest.LogCaptureFixture):
+    class ErrorReader(DummyReader):
+        def _process_record_message(self, message_dict: dict) -> None:  # noqa: ARG002
+            msg = "Bad record"
+            raise ValueError(msg)
+
+    message = RecordMessage(
+        stream="users",
+        record={"id": 1, "value": 1.23},
+    )
+
+    input_lines = io.StringIO(json.dumps(message.to_dict()) + "\n")
+
+    reader = ErrorReader()
+    with caplog.at_level(logging.INFO), pytest.raises(ValueError, match="Bad record"):
+        reader.listen(input_lines)
+
+    assert caplog.records
+
+    message = caplog.records[0].message
+    assert "Failed while processing Singer message" in message
+
+
 def test_write_message():
     writer = SingerWriter()
     message = RecordMessage(