[http-server-javascript] Implement scalar encoding

[witemple-msft]

This PR implements scalar encoders for HSJ.

JsScalar has been significantly expanded from a simple string type to an object that provides scalar encoding data.

The internal API is

const jsScalar = getJsScalar(ctx, module, scalar, diagnosticTarget);

const encoder = jsScalar.getEncoding("<encoding name>", targetScalar);

const encodedExpr = encoder?.encode("<expr>");
const decodedExpr = encoder?.decode("<expr>");

• Encodings are described declaratively using a ScalarInfo data structure that allows:

  • Many different encoding pairs [target, encoding] to be specified for a given scalar.
  • Default encodings for a given target (most scalars implement this for at least string)
  • Default encoding pairs by MIME type.
  • Default encoding pairs for HTTP query/header/cookie/path.
  • Encodings that work via another encoding and automatically stack (base64url for bytes is implemented via: "base64").
  • Encodings that are dependent upon imported types or settings in the emitter options (datetime: temporal in the future?)

• A simple representation of TypeSpec.duration is implemented with ISO 8601-2 parsing.

• Values of scalars with unrecognized encoding are treated as if they are unknown and serialized literally.

WIP checklist:

• Document new scalar APIs thoroughly.
• Implement csv, etc. encoders for query parameters with array types
• Properly validate url encoding/decoding of query/path params.
• Implement DateTime types.

[azure-sdk]

All changed packages have been documented.

• ✅ @typespec/http-server-javascript

Show changes

@typespec/http-server-javascript - feature ✏️

Support encoding/decoding scalar types.

[azure-sdk]

You can try these changes here

🛝 Playground	🌐 Website	📚 Next docs	🛝 VSCode Extension

[markcowl]

I like having issue references with TODO comments, is there an issue we can correlate with this?