From 053e75bca8ef34a655bb4afda5f479f112dfb002 Mon Sep 17 00:00:00 2001
From: Alex Schofield <git@ajschof.me>
Date: Thu, 22 Aug 2024 12:33:00 +0100
Subject: fix: improve error handling for list_existing_s3_files and tests

---
 src/extract_lambda.py        | 16 ++++++++++------
 tests/test_extract_lambda.py | 10 ++++++++--
 2 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/src/extract_lambda.py b/src/extract_lambda.py
index 874098b..b20c99d 100644
--- a/src/extract_lambda.py
+++ b/src/extract_lambda.py
@@ -118,15 +118,16 @@ def list_existing_s3_files(bucket_name=None, client=None):
     results of listing the contents of the s3 bucket, then
     returns the populated dictionary
     """
-    if client is None:
-        client = boto3.client("s3")
-    if bucket_name is None:
-        bucket_name = extract_bucket(client)
 
     logging.info("Listing existing S3 files")
     existing_files = {}
 
     try:
+        if client is None:
+            client = boto3.client("s3")
+        if bucket_name is None:
+            bucket_name = extract_bucket(client)
+
         response = client.list_objects_v2(Bucket=bucket_name)
 
         if "Contents" in response:
@@ -142,8 +143,11 @@ def list_existing_s3_files(bucket_name=None, client=None):
             logger.error("The bucket is empty")
             return None
 
-    except ClientError as e:
-        logger.error(f"Error listing S3 objects: {e}")
+    except ValueError as ve:
+        logger.error(f"Error listing S3 objects: {ve}")
+        raise
+    except ClientError as ce:
+        logger.error(f"Error listing S3 objects: {ce}")
 
     return existing_files
 
diff --git a/tests/test_extract_lambda.py b/tests/test_extract_lambda.py
index bba433c..8fa0e88 100644
--- a/tests/test_extract_lambda.py
+++ b/tests/test_extract_lambda.py
@@ -195,8 +195,14 @@ class TestListExistingS3Files:
         logger.info("Testing now.")
         caplog.set_level(logging.ERROR)
 
-        with pytest.raises(ValueError, match="No extract_bucket found"):
-            list_existing_s3_files(client=s3_client)
+        # Mock the extract_bucket function to raise a ValueError!
+        with patch(
+            "src.extract_lambda.extract_bucket",
+            side_effect=ValueError("No extract_bucket found"),
+        ):
+            with pytest.raises(ValueError, match="No extract_bucket found"):
+                list_existing_s3_files(client=s3_client)
+
         assert "Error listing S3 objects" in caplog.text
 
     def test_error_if_bucket_is_empty(self, s3_client, caplog, s3_mock_bucket):
-- 
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