feat(codegen): add serde helper function

[kuhe]

Issue

n/a

Description

This adds a serde helper called take. The anticipated usage is as follows:

current:

  {
    CreationDateTime:
      output.CreationDateTime != null
        ? __expectNonNull(__parseEpochTimestamp(__expectNumber(output.CreationDateTime)))
        : undefined,
    GlobalTableArn: __expectString(output.GlobalTableArn),
    GlobalTableName: __expectString(output.GlobalTableName),
    GlobalTableStatus: __expectString(output.GlobalTableStatus),
    ReplicationGroup:
      output.ReplicationGroup != null
        ? deserializeAws_json1_0ReplicaDescriptionList(output.ReplicationGroup, context)
        : undefined,
  }

new:

  take(output, {
    CreationDateTime: [, _ => __expectNonNull(__parseEpochTimestamp(__expectNumber(_)))],
    GlobalTableArn: __expectString,
    GlobalTableName: __expectString, // single fn is equivalent to [,fn,]
    GlobalTableStatus: __expectString,
    ReplicationGroup: [, _ => deserializeAws_json1_0ReplicaDescriptionList(_, context)]
  });

The use of tuples as instructions (essentially arguments) is for consistency in reading positional values, and brevity.

[filter function, mapping function, source key]

the default form can be reduced from [void 0, void 0, void 0] to [,,] and further to [], which is shorter than void 0.

Testing

existing and new unit tests

[mtdowling]

Would this account for the use of @jsonName, or is this only for protocols where the name always matches what's on the wire? Does this belong in smithy-typescript too?

[kuhe]

Does this belong in smithy-typescript too?

Yes, this should migrate over with its module when that happens.

Would this account for the use of @jsonName, or is this only for protocols where the name always matches what's on the wire?

It should handle name differences between the source and target.

const source = {
  succinct: 'value 1',
  VERBOSE: 'value 2' 
};

const result = take(source, {
  succinct: [], // default instruction
  verbose: [_ => _ === 'value 2', _ => _ + ' append this', 'VERBOSE'] // verbose instruction
});

result == {
  succinct: 'value 1',
  verbose: 'value 2 append this'
}

The instruction is a triplet of [valueFilter, valueMapper, sourceKey] where the defaults are [nonNullish, passThrough, same key]

[kuhe]

Applying this for example to Lambda's client, the npm pack package size without downlevel types goes from 151kb to 143kb.
The protocol file itself differs in wc as follows:

before/after

7407  24492 360472 dist-cjs/protocols/Aws_restJson1.js
6393  20720 317862 dist-cjs/protocols/Aws_restJson1.js

Example diff: #4620

[github-actions]

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