Clean up some of the encoder logic

packages/http-server-javascript/src/common/scalar.ts

@@ -579,7 +579,7 @@ export interface Encoder {
 export interface JsScalar {
   readonly type: string;
 
-  readonly scalar?: Scalar;
+  readonly scalar: Scalar | "unknown";
 
   getEncoding(encoding: string, target: Scalar): Encoder | undefined;
 
@@ -601,8 +601,12 @@ const DEFAULT_STRING_ENCODER_RAW: Omit<Encoder, "target"> = {
   },
 };
 
+/**
+ * A JsScalar value that represents an unknown scalar.
+ */
 export const JSSCALAR_UNKNOWN: JsScalar = {
   type: "unknown",
+  scalar: "unknown",
   getEncoding: () => undefined,
   getDefaultMimeEncoding: () => undefined,
   http: {

packages/http-server-javascript/src/common/serialization/json.ts

@@ -165,11 +165,10 @@ function* emitToJson(
           const scalarEncoder = scalar.getEncoding(encoding.encoding ?? "default", encoding.type);
 
           if (scalarEncoder) {
-            // Scalar must be defined here because we resolved an encoding. It can only be undefined when it comes
-            // from an `unknown` rendering, which cannot appear in a resolved encoding.
             expr = transposeExpressionToJson(
               ctx,
-              scalarEncoder.target.scalar!,
+              // Assertion: scalarEncoder.target.scalar is defined because we resolved an encoder.
+              scalarEncoder.target.scalar as Scalar,
               scalarEncoder.encode(expr),
               module,
             );
@@ -267,7 +266,8 @@ function transposeExpressionToJson(
       if (encoder.target.isJsonCompatible || !encoder.target.scalar) {
         return encoded;
       } else {
-        return transposeExpressionToJson(ctx, encoder.target.scalar, encoded, module);
+        // Assertion: encoder.target.scalar is a scalar because "unknown" is JSON compatible.
+        return transposeExpressionToJson(ctx, encoder.target.scalar as Scalar, encoded, module);
       }
     case "Union":
       if (!requiresJsonSerialization(ctx, module, type)) {
@@ -401,7 +401,8 @@ function* emitFromJson(
           if (scalarEncoder) {
             expr = transposeExpressionFromJson(
               ctx,
-              scalarEncoder.target.scalar!,
+              // Assertion: scalarEncoder.target.scalar is defined because we resolved an encoder.
+              scalarEncoder.target.scalar as Scalar,
               scalarEncoder.decode(expr),
               module,
             );
@@ -416,7 +417,7 @@ function* emitFromJson(
               },
             });
 
-            // We treat this as unknown from here on out. The encoding was not decipher
+            // We treat this as unknown from here on out. The encoding was not deciphered.
           }
         } else {
           expr = transposeExpressionFromJson(ctx, property.type, expr, module);
@@ -505,7 +506,8 @@ function transposeExpressionFromJson(
       if (encoder.target.isJsonCompatible || !encoder.target.scalar) {
         return decoded;
       } else {
-        return transposeExpressionFromJson(ctx, encoder.target.scalar, decoded, module);
+        // Assertion: encoder.target.scalar is a scalar because "unknown" is JSON compatible.
+        return transposeExpressionFromJson(ctx, encoder.target.scalar as Scalar, decoded, module);
       }
     case "Union":
       if (!requiresJsonSerialization(ctx, module, type)) {