[New] Ensure RegExp#toString is compliant.

paulmillr · Feb 12, 2016 · d310b25 · d310b25
1 parent 5333255
commit d310b25
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diff --git a/README.md b/README.md
@@ -47,6 +47,7 @@ In both browser and node you may also want to include `unorm`; see the [`String.
     * `[Symbol.replace]` (requires native `Symbol`s)
     * `[Symbol.search]` (requires native `Symbol`s)
     * `[Symbol.split]` (requires native `Symbol`s)
+    * `toString`
 * `Number`:
     * binary and octal literals: `Number('0b1')` and `Number('0o7')`
     * `EPSILON`

diff --git a/es6-shim.js b/es6-shim.js
@@ -1743,6 +1743,26 @@
     return RegExp(regex) === regex;
   }());
 
+  var regexToStringIsGeneric = valueOrFalseIfThrows(function () {
+    return RegExp.prototype.toString.call({ source: 'abc' }) === '/abc/';
+  });
+  var regexToStringSupportsGenericFlags = regexToStringIsGeneric && valueOrFalseIfThrows(function () {
+    return RegExp.prototype.toString.call({ source: 'a', flags: 'b' }) === '/a/b';
+  });
+  if (!regexToStringIsGeneric || !regexToStringSupportsGenericFlags) {
+    var origRegExpToString = RegExp.prototype.toString;
+    defineProperty(RegExp.prototype, 'toString', function toString() {
+      var R = ES.RequireObjectCoercible(this);
+      if (Type.regex(R)) {
+        return _call(origRegExpToString, R);
+      }
+      var pattern = $String(R.source);
+      var flags = $String(R.flags);
+      return '/' + pattern + '/' + flags;
+    }, true);
+    Value.preserveToString(RegExp.prototype.toString, origRegExpToString);
+  }
+
   if (supportsDescriptors && (!regExpSupportsFlagsWithRegex || regExpNeedsToSupportSymbolMatch)) {
     var flagsGetter = Object.getOwnPropertyDescriptor(RegExp.prototype, 'flags').get;
     var sourceDesc = Object.getOwnPropertyDescriptor(RegExp.prototype, 'source') || {};

diff --git a/test/regexp.js b/test/regexp.js
@@ -269,6 +269,35 @@ describe('RegExp', function () {
     });
   });
 
+  describe('#toString()', function () {
+    it('throws on null/undefined', function () {
+      expect(function () { RegExp.prototype.toString.call(null); }).to['throw'](TypeError);
+      expect(function () { RegExp.prototype.toString.call(undefined); }).to['throw'](TypeError);
+    });
+
+    it('works on regexes', function () {
+      expect(RegExp.prototype.toString.call(/a/g)).to.equal('/a/g');
+      expect(RegExp.prototype.toString.call(new RegExp('a', 'g'))).to.equal('/a/g');
+    });
+
+    it('works on non-regexes', function () {
+      expect(RegExp.prototype.toString.call({ source: 'abc', flags: '' })).to.equal('/abc/');
+      expect(RegExp.prototype.toString.call({ source: 'abc', flags: 'xyz' })).to.equal('/abc/xyz');
+    });
+
+    ifSymbolsDescribe('Symbol.match', function () {
+      if (!hasSymbols || typeof Symbol.match === 'undefined') {
+        return;
+      }
+
+      it('accepts a non-regex with Symbol.match', function () {
+        var obj = { source: 'abc', flags: 'def' };
+        obj[Symbol.match] = RegExp.prototype[Symbol.match];
+        expect(RegExp.prototype.toString.call(obj)).to.equal('/abc/def');
+      });
+    });
+  });
+
   describe('Object properties', function () {
     it('does not have the nonstandard $input property', function () {
       expect(RegExp).not.to.have.property('$input'); // Chrome < 39, Opera < 26 have this