Serialize empty strings

[Hazelfire]

Fixes #144, allowing empty strings to be included in the serialization.

This seems to be an explicit bug, I am not sure why these statements would be here

[ramosbugs]

I suspect it's because of this quirk of PutRequest inside BatchWriteItem:

Attribute values must not be null; string and binary type attributes must have lengths greater than zero; and set type attributes must not be empty. Requests that contain empty values are rejected with a ValidationException exception.

https://docs.aws.amazon.com/amazondynamodb/latest/APIReference/API_BatchWriteItem.html#API_BatchWriteItem_RequestParameters

however, regular PutItem requests do support empty strings:

Empty String and Binary attribute values are allowed.

https://docs.aws.amazon.com/amazondynamodb/latest/APIReference/API_PutItem.html#API_PutItem_RequestParameters

I'm running into the same issue as @Hazelfire. my suggestion would be either to have two modes of serialization, or to allow serializing empty strings and to make it the caller's responsibility to use, e.g., #[serde(skip_serializing_if = "...")] to avoid serializing empty strings when using BatchWriteItem. thoughts?

[veedubyou]

I'm running into the same issue as @Hazelfire. my suggestion would be either to have two modes of serialization, or to allow serializing empty strings and to make it the caller's responsibility to use, e.g., #[serde(skip_serializing_if = "...")] to avoid serializing empty strings when using BatchWriteItem. thoughts?

imo it makes little sense to let the library silently side step these validation issues - if there was an error then either the library should just let dynamodb report it back, or the library itself should return a failure. I imagine if I did a batch write with many items and some empty string attributes, I'd be very surprised to see my attribute missing in the bulk of my items on later retrieval.

[Hazelfire]

I believe that is actually a documentation error (PutRequest inside BatchWriteItem). I tested it and PutRequest in BatchWriteItem allows for empty attributes.

This seems to be here due to an oversight in changing to support this in 2018 (citing aws/aws-sdk-java#1189). So the best way to proceed is to merge this request to reflect the change in behavior.

I submitted feedback on this documentation for AWS.

[mockersf]

thank you for checking this!