util: fix %s format behavior with Symbol.toPrimitive

This commit ensures `console.log("%s", obj)` correctly invokes `obj[Symbol.toPrimitive]` for string conversion, fixing unexpected object display issue. PR-URL: #50992Fixes: #50909 Reviewed-By: Ruben Bridgewater <[email protected]> Reviewed-By: Chengzhong Wu <[email protected]> Reviewed-By: James M Snell <[email protected]> Reviewed-By: Zeyu "Alex" Yang <[email protected]>

Author: Chenyu Yang

lib/internal/util/inspect.js

@@ -87,6 +87,7 @@ const{
  SymbolPrototypeToString,
  SymbolPrototypeValueOf,
  SymbolIterator,
+ SymbolToPrimitive,
  SymbolToStringTag,
  TypedArrayPrototypeGetLength,
  TypedArrayPrototypeGetSymbolToStringTag,
@@ -2103,6 +2104,11 @@ function hasBuiltInToString(value){
 value=proxyTarget;
 }
 
+// Check if value has a custom Symbol.toPrimitive transformation.
+if(typeofvalue[SymbolToPrimitive]==='function'){
+returnfalse;
+}
+
 // Count objects that have no `toString` function as built-in.
 if(typeofvalue.toString!=='function'){
 returntrue;

test/parallel/test-util-format.js

@@ -269,6 +269,27 @@ assert.strictEqual(util.format('%s', -Infinity), '-Infinity');
 );
 }
 
+// Symbol.toPrimitive handling for string format specifier
+{
+constobjectWithToPrimitive={
+[Symbol.toPrimitive](hint){
+switch(hint){
+case'number':
+return42;
+case'string':
+return'string representation';
+case'default':
+default:
+return'default context';
+}
+}
+};
+
+assert.strictEqual(util.format('%s',+objectWithToPrimitive),'42');
+assert.strictEqual(util.format('%s',objectWithToPrimitive),'string representation');
+assert.strictEqual(util.format('%s',objectWithToPrimitive+''),'default context');
+}
+
 // JSON format specifier
 assert.strictEqual(util.format('%j'),'%j');
 assert.strictEqual(util.format('%j',42),'42');