Address feedback

lib/tools.js

@@ -520,6 +520,22 @@ function setMetadataProps (dest, that) {
   }
 }
 
+/**
+ * Convert a string integer file descriptor to a proper native integer
+ * file descriptor.
+ *
+ * @param {string} destination The file descriptor string to attempt to convert.
+ *
+ * @returns {Number}
+ */
+function normalizeDestFileDescriptor (destination) {
+  const fd = Number(destination)
+  if (typeof destination === 'string' && Number.isFinite(fd)) {
+    return fd
+  }
+  return destination
+}
+
 module.exports = {
   noop,
   buildSafeSonicBoom,
@@ -530,5 +546,6 @@ module.exports = {
   createArgsNormalizer,
   final,
   stringify,
-  buildFormatters
+  buildFormatters,
+  normalizeDestFileDescriptor
 }

pino.js

@@ -15,8 +15,9 @@ const {
   final,
   buildSafeSonicBoom,
   buildFormatters,
-  noop,
-  stringify
+  stringify,
+  normalizeDestFileDescriptor,
+  noop
 } = require('./lib/tools')
 const { version } = require('./lib/meta')
 const {
@@ -191,10 +192,10 @@ module.exports = pino
 
 module.exports.destination = (dest = process.stdout.fd) => {
   if (typeof dest === 'object') {
-    dest.dest = dest.dest || process.stdout.fd
+    dest.dest = normalizeDestFileDescriptor(dest.dest || process.stdout.fd)
     return buildSafeSonicBoom(dest)
   } else {
-    return buildSafeSonicBoom({ dest, minLength: 0, sync: true })
+    return buildSafeSonicBoom({ dest: normalizeDestFileDescriptor(dest), minLength: 0, sync: true })
   }
 }