Merge pull request #266 from PejmanNik/adding-support-for-nonstandard-map-key-in-the-decoder

adding support for nonstandard map key in the decoder

Author: gfx

README.md

@@ -145,17 +145,20 @@ NodeJS `Buffer` is also acceptable because it is a subclass of `Uint8Array`.
 
 #### `DecoderOptions`
 
-| Name | Type | Default |
-| -------------- | -------------- | ----------------------------- |
-| extensionCodec | ExtensionCodec | `ExtensionCodec.defaultCodec` |
-| context | user-defined | - |
-| useBigInt64 | boolean | false |
-| rawStrings | boolean | false |
-| maxStrLength | number | `4_294_967_295` (UINT32_MAX) |
-| maxBinLength | number | `4_294_967_295` (UINT32_MAX) |
-| maxArrayLength | number | `4_294_967_295` (UINT32_MAX) |
-| maxMapLength | number | `4_294_967_295` (UINT32_MAX) |
-| maxExtLength | number | `4_294_967_295` (UINT32_MAX) |
+| Name | Type | Default |
+| --------------- | ------------------- | ---------------------------------------------- |
+| extensionCodec | ExtensionCodec | `ExtensionCodec.defaultCodec` |
+| context | user-defined | - |
+| useBigInt64 | boolean | false |
+| rawStrings | boolean | false |
+| maxStrLength | number | `4_294_967_295` (UINT32_MAX) |
+| maxBinLength | number | `4_294_967_295` (UINT32_MAX) |
+| maxArrayLength | number | `4_294_967_295` (UINT32_MAX) |
+| maxMapLength | number | `4_294_967_295` (UINT32_MAX) |
+| maxExtLength | number | `4_294_967_295` (UINT32_MAX) |
+| mapKeyConverter | MapKeyConverterType | throw exception if key is not string or number |
+
+`MapKeyConverterType` is defined as `(key: unknown) => string | number`.
 
 To skip UTF-8 decoding of strings, `rawStrings` can be set to `true`. In this case, strings are decoded into `Uint8Array`.
 

src/Decoder.ts

@@ -68,6 +68,13 @@ export type DecoderOptions<ContextType = undefined> = Readonly<
  * `null` is a special value to disable the use of the key decoder at all.
  */
  keyDecoder: KeyDecoder | null;
+
+ /**
+ * A function to convert decoded map key to a valid JS key type.
+ * 
+ * Defaults to a function that throws an error if the key is not a string or a number.
+ */
+ mapKeyConverter: (key: unknown) => MapKeyType;
  }>
 > &
  ContextOf<ContextType>;
@@ -78,8 +85,11 @@ const STATE_MAP_VALUE = "map_value";
 
 type MapKeyType = string | number;
 
-const isValidMapKeyType = (key: unknown): key is MapKeyType => {
- return typeof key === "string" || typeof key === "number";
+const mapKeyConverter = (key: unknown): MapKeyType => {
+ if (typeof key === "string" || typeof key === "number") {
+ return key;
+ }
+ throw new DecodeError("The type of key must be string or number but " + typeof key);
 };
 
 type StackMapState = {
@@ -213,6 +223,7 @@ export class Decoder<ContextType = undefined> {
  private readonly maxMapLength: number;
  private readonly maxExtLength: number;
  private readonly keyDecoder: KeyDecoder | null;
+ private readonly mapKeyConverter: (key: unknown) => MapKeyType;
 
  private totalPos = 0;
  private pos = 0;
@@ -236,6 +247,7 @@ export class Decoder<ContextType = undefined> {
  this.maxMapLength = options?.maxMapLength ?? UINT32_MAX;
  this.maxExtLength = options?.maxExtLength ?? UINT32_MAX;
  this.keyDecoder = options?.keyDecoder !== undefined ? options.keyDecoder : sharedCachedKeyDecoder;
+ this.mapKeyConverter = options?.mapKeyConverter ?? mapKeyConverter;
  }
 
  private clone(): Decoder<ContextType> {
@@ -631,14 +643,11 @@ export class Decoder<ContextType = undefined> {
  continue DECODE;
  }
  } else if (state.type === STATE_MAP_KEY) {
- if (!isValidMapKeyType(object)) {
- throw new DecodeError("The type of key must be string or number but " + typeof object);
- }
  if (object === "__proto__") {
  throw new DecodeError("The key __proto__ is not allowed");
  }
 
- state.key = object;
+ state.key = this.mapKeyConverter(object);
  state.type = STATE_MAP_VALUE;
  continue DECODE;
  } else {

test/decodeAsync.test.ts

@@ -36,6 +36,21 @@ describe("decodeAsync", () => {
  assert.deepStrictEqual(object, { "foo": "bar" });
  });
 
+ it("decodes fixmap {'[1, 2]': 'baz'} with custom map key converter", async () => {
+ const createStream = async function* () {
+ yield [0x81]; // fixmap size=1
+ yield encode([1, 2]);
+ yield encode("baz");
+ };
+
+ const object = await decodeAsync(createStream(), {
+ mapKeyConverter: (key) => JSON.stringify(key),
+ });
+
+ const key = JSON.stringify([1, 2]);
+ assert.deepStrictEqual(object, { [key]: "baz" });
+ });
+
  it("decodes multi-byte integer byte-by-byte", async () => {
  const createStream = async function* () {
  yield [0xcd]; // uint 16