path: the dot will be added(path.format) if it is not specified in ext

PR-URL: #44349Fixes: #44343
Reviewed-By: Moshe Atlow <moshe@atlow.co.il>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Geoffrey Booth <webadmin@geoffreybooth.com>

Author: theanarkh

doc/api/path.md

@@ -206,6 +206,10 @@ A [`TypeError`][] is thrown if `path` is not a string.
 
 <!-- YAML
 added: v0.11.15
+changes:
+ - version: REPLACEME
+ pr-url: https://github.com/nodejs/node/pull/44349
+ description: The dot will be added if it is not specified in `ext`.
 -->
 
 *`pathObject` {Object} Any JavaScript object having the following properties:
@@ -255,6 +259,14 @@ path.format({
  ext:'.txt'
 });
 // Returns: '/file.txt'
+
+// The dot will be added if it is not specified in `ext`.
+path.format({
+ root:'/',
+ name:'file',
+ ext:'txt'
+});
+// Returns: '/file.txt'
 ```
 
 On Windows:

lib/path.js

@@ -127,6 +127,10 @@ function normalizeString(path, allowAboveRoot, separator, isPathSeparator) {
 returnres;
 }
 
+functionformatExt(ext){
+returnext ? `${ext[0]==='.' ? '' : '.'}${ext}` : '';
+}
+
 /**
  * @param {string} sep
  * @param {{
@@ -142,7 +146,7 @@ function _format(sep, pathObject) {
 validateObject(pathObject,'pathObject');
 constdir=pathObject.dir||pathObject.root;
 constbase=pathObject.base||
-`${pathObject.name||''}${pathObject.ext||''}`;
+`${pathObject.name||''}${formatExt(pathObject.ext)}`;
 if(!dir){
 returnbase;
 }

test/parallel/test-path-parse-format.js

@@ -224,3 +224,7 @@ function checkFormat(path, testCases) {
 });
 });
 }
+
+// See https://github.com/nodejs/node/issues/44343
+assert.strictEqual(path.format({name: 'x',ext: 'png'}),'x.png');
+assert.strictEqual(path.format({name: 'x',ext: '.png'}),'x.png');