Sparse traits not considered when generating Records for Map shapes

[miloszwatroba]

Hi,

I'd like to report a bug in the smithy-typescript-codegen package.

@sparse traits added to the Map shapes (https://smithy.io/2.0/spec/type-refinement-traits.html#sparse-trait) are not reflected by TypeScript Records generated by smithy-typescript-codegen.

For instance, the following definition:

structure ExampleStructure {
    sparseMap: SparseMap,
}

@sparse
map SparseMap {
    key: String,
    value: String
}

results in the following TypeScript code:

export interface ExampleStructure {
    environment?: Record<string, string>;
}

while according to the specification ("sparse Indicates that lists and maps MAY contain null values. The sparse trait has no effect on map keys; map keys are never allowed to be null."), it should rather generate the following:

export interface ExampleStructure {
    environment?: Record<string, string | null>;
}

Tested with latest version: 0.19.0

Cheers,
Milosz