fix: Serialization of decimal.Decimal (#1826)

Co-authored-by: Pat Nadolny <[email protected]>

singer_sdk/batch.py

@@ -104,7 +104,8 @@ def get_batches(
                     mode="wb",
                 ) as gz:
                     gz.writelines(
-                        (json.dumps(record) + "\n").encode() for record in chunk
+                        (json.dumps(record, default=str) + "\n").encode()
+                        for record in chunk
                     )
                 file_url = fs.geturl(filename)
             yield [file_url]

tests/core/test_batch.py

@@ -1,11 +1,15 @@
 from __future__ import annotations
 
+import decimal
+import re
 from dataclasses import asdict
 
 import pytest
 
+from singer_sdk.batch import JSONLinesBatcher
 from singer_sdk.helpers._batch import (
     BaseBatchFileEncoding,
+    BatchConfig,
     JSONLinesEncoding,
     StorageTarget,
 )
@@ -95,3 +99,29 @@ def test_storage_from_url(file_url: str, root: str):
 def test_storage_split_url(file_url: str, expected: tuple):
     """Test storage target split URL."""
     assert StorageTarget.split_url(file_url) == expected
+
+
+def test_json_lines_batcher():
+    batcher = JSONLinesBatcher(
+        "tap-test",
+        "stream-test",
+        batch_config=BatchConfig(
+            encoding=JSONLinesEncoding("gzip"),
+            storage=StorageTarget("file:///tmp/sdk-batches"),
+            batch_size=2,
+        ),
+    )
+    records = [
+        {"id": 1, "numeric": decimal.Decimal("1.0")},
+        {"id": 2, "numeric": decimal.Decimal("2.0")},
+        {"id": 3, "numeric": decimal.Decimal("3.0")},
+    ]
+
+    batches = list(batcher.get_batches(records))
+    assert len(batches) == 2
+    assert all(len(batch) == 1 for batch in batches)
+    assert all(
+        re.match(r".*tap-test--stream-test-.*\.json.gz", filepath)
+        for batch in batches
+        for filepath in batch
+    )