fix 'trying to remove refId with 0 refCount' at decoding.

Author: endel

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@colyseus/schema",
-  "version": "3.0.16",
+  "version": "3.0.17",
   "description": "Binary state serializer with delta encoding for games",
   "bin": {
     "schema-codegen": "./bin/schema-codegen",

src/decoder/DecodeOperation.ts

@@ -73,18 +73,6 @@ export function decodeValue(
         const refId = decode.number(bytes, it);
         value = $root.refs.get(refId);
 
-        if (previousValue) {
-            const previousRefId = $root.refIds.get(previousValue);
-            if (
-                previousRefId &&
-                refId !== previousRefId &&
-                // FIXME: we may need to check for REPLACE operation as well
-                ((operation & OPERATION.DELETE) === OPERATION.DELETE)
-            ) {
-                $root.removeRef(previousRefId);
-            }
-        }
-
         if ((operation & OPERATION.ADD) === OPERATION.ADD) {
             const childType = decoder.getInstanceType(bytes, it, type);
             if (!value) {
@@ -101,7 +89,6 @@ export function decodeValue(
             );
         }
 
-
     } else if (typeof(type) === "string") {
         //
         // primitive value (number, string, boolean, etc)
@@ -123,8 +110,6 @@ export function decodeValue(
             let previousRefId = $root.refIds.get(previousValue);
 
             if (previousRefId !== undefined && refId !== previousRefId) {
-                $root.removeRef(previousRefId);
-
                 //
                 // enqueue onRemove if structure has been replaced.
                 //
@@ -153,7 +138,10 @@ export function decodeValue(
             }
         }
 
-        $root.addRef(refId, value, (valueRef !== previousValue));
+        $root.addRef(refId, value, (
+            valueRef !== previousValue ||
+            (operation === OPERATION.DELETE_AND_ADD && valueRef === previousValue)
+        ));
     }
 
     return { value, previousValue };

test/InstanceSharing.test.ts

@@ -1,7 +1,7 @@
 import * as assert from "assert";
 import { Schema, type, ArraySchema, MapSchema, Reflection } from "../src";
 import { $changes } from "../src/types/symbols";
-import { assertDeepStrictEqualEncodeAll, createInstanceFromReflection, getCallbacks, getDecoder, getEncoder } from "./Schema";
+import { assertDeepStrictEqualEncodeAll, assertRefIdCounts, createInstanceFromReflection, getCallbacks, getDecoder, getEncoder } from "./Schema";
 
 describe("Instance sharing", () => {
     class Position extends Schema {
@@ -71,6 +71,8 @@ describe("Instance sharing", () => {
 
         }, decodedState.toJSON());
 
+        assertRefIdCounts(state, decodedState);
+
         assert.strictEqual(5, decoder.root.refs.size, "Player and Position structures should remain.");
         assertDeepStrictEqualEncodeAll(state);
     });
@@ -105,6 +107,7 @@ describe("Instance sharing", () => {
         for (let refId in decoder.root.refCounts) {
             assert.strictEqual(decoder.root.refCounts[refId], encoder.root.refCount[refId]);
         }
+        assertRefIdCounts(state, decodedState);
 
         assertDeepStrictEqualEncodeAll(state);
     });
@@ -454,6 +457,7 @@ describe("Instance sharing", () => {
 
             decodedState.decode(state.encode());
             assert.deepStrictEqual(state.toJSON(), decodedState.toJSON());
+            assertRefIdCounts(state, decodedState);
 
             assertDeepStrictEqualEncodeAll(state);
         });

test/Schema.ts

@@ -33,11 +33,25 @@ export function assertDeepStrictEqualEncodeAll(state: Schema) {
     freshDecode.decode(encodeAll);
     assert.deepStrictEqual(freshDecode.toJSON(), state.toJSON());
 
+    assertRefIdCounts(state, freshDecode);
+
     // // perform a regular encode right full decode
     // freshDecode.decode(state.encode());
     // assert.deepStrictEqual(freshDecode.toJSON(), state.toJSON());
 }
 
+export function assertRefIdCounts(source: Schema, target: Schema) {
+    // assert ref counts
+    const encoder = getEncoder(source);
+    const decoder = getDecoder(target);
+
+    for (const refId in encoder.root.refCount) {
+        const encoderRefCount = encoder.root.refCount[refId];
+        const decoderRefCount = decoder.root.refCounts[refId] ?? 0;
+        assert.strictEqual(encoderRefCount, decoderRefCount, `refCount mismatch for ${refId}`);
+    }
+}
+
 export function getEncoder(state: Schema) {
     if (!state['_encoder']) { state['_encoder'] = new Encoder(state); }
     return state['_encoder'] as Encoder;