Revert EC2 Query Protocol empty list serialization

[syall]

Overview

Revert EC2 Query Protocol empty list serialization.

Empty lists are NOT serialized for the EC2 query protocol, which differs from the AWS query protocol.
See "EmptyQueryLists" for the AWS query protocol equivalent test case.

This is needed since SDKs that conform to the broken protocol tests will send invalid requests to EC2.

Testing

Tested with aws-sdk-js-v3 locally (smithy-typescript, aws-sdk-js-v3) sending a previously failing command with the error InvalidRequest: The request received was invalid. now with the correct validation error.

const { EC2Client: Client, DescribeKeyPairsCommand: Command } = require("@aws-sdk/client-ec2");

(async () => {
    const client = new Client();
    client.middlewareStack.add(next => async (args) => {
        console.info(args.request.body);
        return await next(args);
    }, { step: 'finalizeRequest' });
    try {
        await client.send(new Command({
            Filters: [],
            KeyPairIds: ["key-KEYISNOTREALATALL"],
        }));
    } catch (error) {
        console.error(error);
    }
})();

Before:

Filter=&KeyPairId.1=key-KEYISNOTREALATALL&Action=DescribeKeyPairs&Version=2016-11-15
InvalidRequest: The request received was invalid.

After:

KeyPairId.1=key-KEYISNOTREALATALL&Action=DescribeKeyPairs&Version=2016-11-15
InvalidParameterValue: Invalid value 'key-KEYISNOTREALATALL' for keyPairId.

The Filter= empty list serialization is removed.

- Filter=&KeyPairId.1=key-KEYISNOTREALATALL&Action=DescribeKeyPairs&Version=2016-11-15
+ KeyPairId.1=key-KEYISNOTREALATALL&Action=DescribeKeyPairs&Version=2016-11-15

Links

• AWS EC2 Query Protocol: https://smithy.io/2.0/aws/protocols/aws-ec2-query-protocol.html
• Original empty list serialization PR: Reverse the logic of the protocol test to be in sync with the current… #1444
• Customer reports from AWS SDK for Go v2: Bad request when describe key pairs with empty filters slice aws/aws-sdk-go-v2#2624 RevokeSecurityGroupEgress and AuthorizeSecurityGroupEgress requests not working aws/aws-sdk-go-v2#2559
• Botocore AWS EC2 Query Protocol List serialization: https://github.com/boto/botocore/blob/develop/botocore/serialize.py#L337
• Botocore AWS Query Protocol List serialization: https://github.com/boto/botocore/blob/develop/botocore/serialize.py#L259

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