util: allow single-line format when break length is infinite

Signed-off-by: Hamid Reza Ghavami <hamidr.ghavami@gmail.com>

Author: hamidrezaghavami

lib/internal/util/inspect.js

@@ -2624,6 +2624,14 @@ function isBelowBreakLength(ctx, output, start, base) {
   // TODO(BridgeAR): Add unicode support. Use the readline getStringWidth
   // function. Check the performance overhead and make it an opt-in in case it's
   // significant.
+  // allow the single-line format if the length limit is infinite and no items have newlines
+  if (ctx.breakLength === Infinity) {
+    if (base !== '' && StringPrototypeIncludes(base, '\n')) return false;
+    for (let i = 0; i < output.length; i++) {
+      if (typeof output[i] === 'string' && StringPrototypeIncludes(output[i], '\n')) return false;
+    }
+    return true;
+  }
   let totalLength = output.length + start;
   if (totalLength + output.length > ctx.breakLength)
     return false;

test/parallel/test-util-inspect.js

@@ -4058,3 +4058,15 @@ ${error.stack.split('\n').slice(1).join('\n')}`,
   assert.match(inspect(DOMException.prototype), /^\[object DOMException\] \{/);
   delete Error[Symbol.hasInstance];
 }
+
+{
+    // Ensure breakLength: Infinity formats deeply nested objects on a single line
+    // while properly preserving multi-line outer formatting if inner items have newlines.
+    const nestedObj = { a: { b: { c: [1, 2, 'long string '.repeat(50)] } } };
+    const singleLine = util.inspect(nestedObj, { breakLength: Infinity });
+    assert.ok(!singleLine.includes('\n'));
+
+    const multilineObj = { first: 'hello\nworld', second: 'foo' };
+    const multiLine = util.inspect(multilineObj, { breakLength: Infinity });
+    assert.ok(multiLine.startsWith('{\n'));
+  }