Normative: integrate well-formed Unicode strings proposal (#3039)

Author: michaelficarra

spec.html

@@ -34033,6 +34033,16 @@ <h1>String.prototype.indexOf ( _searchString_ [ , _position_ ] )</h1>
         </emu-note>
       </emu-clause>
 
+      <emu-clause id="sec-string.prototype.iswellformed">
+        <h1>String.prototype.isWellFormed ( )</h1>
+        <p>This method performs the following steps when called:</p>
+        <emu-alg>
+          1. Let _O_ be ? RequireObjectCoercible(*this* value).
+          1. Let _S_ be ? ToString(_O_).
+          1. Return IsStringWellFormedUnicode(_S_).
+        </emu-alg>
+      </emu-clause>
+
       <emu-clause id="sec-string.prototype.lastindexof">
         <h1>String.prototype.lastIndexOf ( _searchString_ [ , _position_ ] )</h1>
         <emu-note>
@@ -34606,6 +34616,27 @@ <h1>String.prototype.toUpperCase ( )</h1>
         </emu-note>
       </emu-clause>
 
+      <emu-clause id="sec-string.prototype.towellformed">
+        <h1>String.prototype.toWellFormed ( )</h1>
+        <p>This method returns a String representation of this object with all leading surrogates and trailing surrogates that are not part of a surrogate pair replaced with U+FFFD (REPLACEMENT CHARACTER).</p>
+        <p>It performs the following steps when called:</p>
+        <emu-alg>
+          1. Let _O_ be ? RequireObjectCoercible(*this* value).
+          1. Let _S_ be ? ToString(_O_).
+          1. Let _strLen_ be the length of _S_.
+          1. Let _k_ be 0.
+          1. Let _result_ be the empty String.
+          1. Repeat, while _k_ &lt; _strLen_,
+            1. Let _cp_ be CodePointAt(_S_, _k_).
+            1. If _cp_.[[IsUnpairedSurrogate]] is *true*, then
+              1. Set _result_ to the string-concatenation of _result_ and 0xFFFD (REPLACEMENT CHARACTER).
+            1. Else,
+              1. Set _result_ to the string-concatenation of _result_ and UTF16EncodeCodePoint(_cp_.[[CodePoint]]).
+            1. Set _k_ to _k_ + _cp_.[[CodeUnitCount]].
+          1. Return _result_.
+        </emu-alg>
+      </emu-clause>
+
       <emu-clause id="sec-string.prototype.trim">
         <h1>String.prototype.trim ( )</h1>
         <p>This method interprets a String value as a sequence of UTF-16 encoded code points, as described in <emu-xref href="#sec-ecmascript-language-types-string-type"></emu-xref>.</p>