fix(lib-dynamodb): fix marshalling of list attributes in UpdateCommand

[brendanhonea]

Description

I recently found a bug in the @aws-sdk/lib-dynamodb package (document client) . The UpdateCommand was failing when providing a list attribute to AttributeUpdates. UpdateCommand allows you to supply native attribute values to update a dynamo record like so:

new UpdateCommand({
    TableName: "SomeTable",
    Key: {
      pk: "somePk",
      sk: "someSk",
    },
    AttributeUpdates: {
        stringAttr: { Action: "PUT", Value: "Some string value" },
        numberAttr: { Action: "PUT", Value: 12345 },
        listAttr: { Action: "PUT", Value: ["list item 1", "list item 2"] },
    },
    ReturnValues: "ALL_NEW",
})

The issue I was running in to was that list attributes were not being marshaled properly and causing a JSON parsing error downstream in the library. The marshaler would convert the above AttributeUpdates map into:

AttributeUpdates: {
        stringAttr: { Action: "PUT", Value: {S: "some string value"} },
        numberAttr: { Action: "PUT", Value: { N: "12345"} },
        listAttr: { Action: "PUT", Value: [ { S: "list item 1"} , { S: "list item 2" } ] }, // Here is the problem
    },

The dynamodb client expects lists to also be prefaced with an attribute type like so

AttributeUpdates: {
        stringAttr: { Action: "PUT", Value: {S: "some string value"} },
        numberAttr: { Action: "PUT", Value: { N: "12345"} },
        listAttr: { Action: "PUT", Value: { L: [ { S: "list item 1"} , { S: "list item 2" } ] } }, // This is what dynamodb needs to see
    },

This PR addresses the issue in the lib-dynamo marshaling code so that lists are passed properly to the dynamodb client. I added an optional parameter to the KeyNode type so that this only affects commands that need to process nodes in this fashion.

Testing

I wrote unit tests to ensure that the marshaling works properly and ran the entire test suite to test for breaking changes.

Additional Context

I could not regenerate clients due to Projection ec2.2016-11-15 failed: java.lang.OutOfMemoryError: Java heap space. I don't believe this was caused by my changes as I did not touch any EC2 code.

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[kuhe]

discussed it with Brendan -- the main issue is that the interface of marshall, this function, should not be changed since I have seen that it is used independently.

The option could be implemented as a new marshallOptions entry and applied only to UpdateCommand.

[kuhe]

superceded by #5306

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