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Fix: DynamoDB:GetItem throws wrong error when table doesn't exist #3700

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Feb 17, 2021
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Fix: DynamoDB:GetItem throws wrong error when table doesn't exist #3700

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Fix: DynamoDB:GetItem throws wrong error when table doesn't exist
bpandola Feb 17, 2021
0cdc55b
Use unique exception for table not found, per PR feedback
bpandola Feb 17, 2021
410f4c2
Just fix the reported issue, without touching anything else...
bpandola Feb 17, 2021
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11 changes: 8 additions & 3 deletions moto/dynamodb2/responses.py
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Original file line number Diff line number Diff line change
Expand Up @@ -359,9 +359,14 @@ def get_item(self):

try:
item = self.dynamodb_backend.get_item(name, key, projection_expression)
except ValueError:
er = "com.amazon.coral.validate#ValidationException"
return self.error(er, "Validation Exception")
except ValueError as e:
if str(e) == "No table found":
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Is it possible to throw a custom exception when the table does not exist? I feel like this would be a cleaner approach:

try:
...
except TableNotFound:
...
except ValueError:
...

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That's what I did initially, but unfortunately it breaks other tests. I opted for the simplest solution, though I agree with you that's it's not the most elegant. Fixing this properly requires fairly major surgery, which I'm pretty hesitant to undertake.

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...looked at this again. Decided to just fix the reported issue, without touching anything else. Let me know what you think.

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Yeah, I think this makes sense, to fail as early as possible. Thanks!

er = "com.amazonaws.dynamodb.v20120810#ResourceNotFoundException"
msg = "Requested resource not found"
else:
er = "com.amazon.coral.validate#ValidationException"
msg = "Validation Exception"
return self.error(er, msg)
if item:
item_dict = item.describe_attrs(attributes=None)
item_dict["ConsumedCapacity"] = {"TableName": name, "CapacityUnits": 0.5}
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9 changes: 9 additions & 0 deletions tests/test_dynamodb2/test_dynamodb.py
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Expand Up @@ -5698,3 +5698,12 @@ def test_update_item_add_to_list_using_legacy_attribute_updates():

resp = table.get_item(Key={"id": "list_add"})
resp["Item"]["attr"].should.equal(["a", "b", "c", "d", "e"])


@mock_dynamodb2
def test_get_item_for_non_existent_table_raises_error():
client = boto3.client("dynamodb", "us-east-1")
with pytest.raises(ClientError) as ex:
client.get_item(TableName="non-existent", Key={"site-id": {"S": "foo"}})
ex.value.response["Error"]["Code"].should.equal("ResourceNotFoundException")
ex.value.response["Error"]["Message"].should.equal("Requested resource not found")