A null ExclusiveStartKey produces promise rejection when sending QueryCommand or ScanCommand

[korostelevm]

Describe the bug

When sending a query or scan command with a null value for ExclusiveStartKey, the sdk fails with an unhandled promise rejection. Null values were supported before and are often used in pagination code.

If this change was intended, it should produce a ValidationError with an appropriate message.

Your environment

SDK version number

@aws-sdk/client-dynamodb@3.77
@aws-sdk/lib-dynamodb@3.77

Is the issue in the browser/Node.js/ReactNative?

Node.js

Details of the browser/Node.js/ReactNative version

v14.17.0

Steps to reproduce

This code fails with 3.77 but works in 3.53

const { DynamoDBDocumentClient, QueryCommand , ScanCommand} = require("@aws-sdk/lib-dynamodb")
const { DynamoDBClient } = require("@aws-sdk/client-dynamodb")
const REGION = process.env.AWS_REGION || 'us-east-2'
const ddbClient = new DynamoDBClient({ region: REGION });
const docClient = DynamoDBDocumentClient.from(ddbClient);

let params = {
    TableName: 'table',
    ExclusiveStartKey: null
  };
let res = await docClient.send(new ScanCommand(params))
console.log(res)

Observed behavior

A clear and concise description of what happens.

Resulting error

}
(node:69395) UnhandledPromiseRejectionWarning: TypeError: Cannot read property '0' of undefined
    at Object.AttributeValue.visit (/Users/mike/Dropbox/codes/db-sdk/node_modules/@aws-sdk/client-dynamodb/dist-cjs/models/models_0.js:1319:40)
    at serializeAws_json1_0AttributeValue (/Users/mike/Dropbox/codes/db-sdk/node_modules/@aws-sdk/client-dynamodb/dist-cjs/protocols/Aws_json1_0.js:3134:38)
    at /Users/mike/Dropbox/codes/db-sdk/node_modules/@aws-sdk/client-dynamodb/dist-cjs/protocols/Aws_json1_0.js:3746:20
    at Array.reduce (<anonymous>)
    at serializeAws_json1_0Key (/Users/mike/Dropbox/codes/db-sdk/node_modules/@aws-sdk/client-dynamodb/dist-cjs/protocols/Aws_json1_0.js:3740:34)
    at serializeAws_json1_0QueryInput (/Users/mike/Dropbox/codes/db-sdk/node_modules/@aws-sdk/client-dynamodb/dist-cjs/protocols/Aws_json1_0.js:4069:32)
    at serializeAws_json1_0QueryCommand (/Users/mike/Dropbox/codes/db-sdk/node_modules/@aws-sdk/client-dynamodb/dist-cjs/protocols/Aws_json1_0.js:356:27)
    at serialize (/Users/mike/Dropbox/codes/db-sdk/node_modules/@aws-sdk/client-dynamodb/dist-cjs/commands/QueryCommand.js:30:67)
    at /Users/mike/Dropbox/codes/db-sdk/node_modules/@aws-sdk/middleware-serde/dist-cjs/serializerMiddleware.js:5:27
    at /Users/mike/Dropbox/codes/db-sdk/node_modules/@aws-sdk/middleware-logger/dist-cjs/loggerMiddleware.js:6:28

Expected behavior

A clear and concise description of what you were expecting to happen.
Expected it to behave as if ExclusiveStartKey was not provided and scan/query forward at the index start

Screenshots

If applicable, add screenshots to help explain your problem.

Additional context

Add any other context about the problem here.

[korostelevm]

Looks like this is the change that introduced the issue

aws-sdk-js-v3/lib/lib-dynamodb/src/commands/utils.ts

Line 13 in a5fa267

if (obj !== undefined) {

In #3539 @kuhe @trivikr

[kuhe]

Hi @korostelevm, I'm sorry that this change was breaking for your application.

The change made in #3539 fixes and allows non-map values, and indeed falsy values, to be converted correctly in @aws-sdk/lib-dynamodb, where previously they were unintentionally ignored.

Please leave the key out of your request object when not providing a compatible value. As a second option, use a value of undefined instead of null.

We don't currently plan to add validation, because there is usually no client side runtime type validation. If you use TypeScript with strict null checks, that will block null from being allowed in this case.

[korostelevm]

Thanks for taking a look, faced the original issue in the past as well. Having to choose between workarounds, I think I'll take this one 😂

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