fix(logger): correctly serialize shared object references in JSON replacer (#5186)

Author: svozza

packages/logger/src/Logger.ts

@@ -761,25 +761,29 @@ class Logger extends Utility implements LoggerInterface {
    * @see {@link ConstructorOptions.jsonReplacerFn}
    */
   protected getJsonReplacer(): (key: string, value: unknown) => void {
-    const references = new WeakSet();
+    const ancestors: unknown[] = [];
+    const jsonReplacerFn = this.#jsonReplacerFn;
+    const logFormatter = this.getLogFormatter();
 
-    return (key, value) => {
+    return function (this: unknown, key: string, value: unknown) {
       let replacedValue = value;
-      if (this.#jsonReplacerFn)
-        replacedValue = this.#jsonReplacerFn?.(key, replacedValue);
+      if (jsonReplacerFn) replacedValue = jsonReplacerFn(key, replacedValue);
 
       if (replacedValue instanceof Error) {
-        replacedValue = this.getLogFormatter().formatError(replacedValue);
+        replacedValue = logFormatter.formatError(replacedValue);
       }
       if (typeof replacedValue === 'bigint') {
         return replacedValue.toString();
       }
       if (typeof replacedValue === 'object' && replacedValue !== null) {
+        while (ancestors.length > 0 && ancestors.at(-1) !== this) {
+          ancestors.pop();
+        }
         /* v8 ignore next -- @preserve */
-        if (references.has(replacedValue)) {
+        if (ancestors.includes(replacedValue)) {
           return;
         }
-        references.add(replacedValue);
+        ancestors.push(replacedValue);
       }
 
       return replacedValue;

packages/logger/tests/unit/formatters.test.ts

@@ -727,6 +727,46 @@ describe('Formatters', () => {
 
   // #region custom JSON replacer
 
+  it('correctly serializes shared object references across different keys', () => {
+    // Prepare
+    const x1 = [{ value: '1' }];
+
+    // Act
+    logger.info('foo', { x1, destructed: [...x1] });
+
+    // Assess
+    expect(console.info).toHaveBeenCalledTimes(1);
+    expect(console.info).toHaveLoggedNth(
+      1,
+      expect.objectContaining({
+        level: 'INFO',
+        message: 'foo',
+        x1: [{ value: '1' }],
+        destructed: [{ value: '1' }],
+      })
+    );
+  });
+
+  it('correctly serializes multiple spread arrays sharing the same elements', () => {
+    // Prepare
+    const x1 = [{ value: '1' }];
+
+    // Act
+    logger.info('foo', { destructed1: [...x1], destructed2: [...x1] });
+
+    // Assess
+    expect(console.info).toHaveBeenCalledTimes(1);
+    expect(console.info).toHaveLoggedNth(
+      1,
+      expect.objectContaining({
+        level: 'INFO',
+        message: 'foo',
+        destructed1: [{ value: '1' }],
+        destructed2: [{ value: '1' }],
+      })
+    );
+  });
+
   it('ignores keys with circular references when stringifying', () => {
     // Prepare
     const circularObject = {