Shorthand tags with !! whenever possible

fix #258

Author: rlidwka

CHANGELOG.md

@@ -27,6 +27,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
  `undefined` in mappings, #571.
 - `dump()` with `skipInvalid=true` now serializes invalid items in collections as null.
 - Custom tags starting with `!` are now dumped as `!tag` instead of `!<!tag>`, #576.
+- Custom tags starting with `tag:yaml.org,2002:` are now shorthanded using `!!`, #258.
 
 ### Added
 - Added `.mjs` (es modules) support.

lib/dumper.js

@@ -888,6 +888,8 @@ function writeNode(state, level, object, block, compact, iskey, isblockseq) {
 
  if (state.tag[0] === '!') {
  tagStr = '!' + tagStr;
+ } else if (tagStr.slice(0, 18) === 'tag:yaml.org,2002:') {
+ tagStr = '!!' + tagStr.slice(18);
  } else {
  tagStr = '!<' + tagStr + '>';
  }

test/issues/0258.js

@@ -0,0 +1,26 @@
+'use strict';
+
+
+const assert = require('assert');
+const yaml = require('../../');
+
+
+it('should shorthand tags with !! whenever possible', function () {
+ let regexp = new yaml.Type('tag:yaml.org,2002:js/regexp', {
+ kind: 'scalar',
+ resolve: () => true,
+ construct: str => new RegExp(str),
+ instanceOf: RegExp,
+ represent: object => object.source
+ });
+
+ let schema = yaml.DEFAULT_SCHEMA.extend(regexp);
+
+ let source = 're: !!js/regexp .*\n';
+
+ let object = yaml.load(source, { schema });
+ assert(object.re instanceof RegExp);
+
+ let str = yaml.dump(object, { schema });
+ assert.strictEqual(str, source);
+});