Enhanced String Length Handling (#426)

Author: elliotmjackson

core/src/main/java/org/projectnessie/cel/common/types/StringT.java

@@ -203,7 +203,7 @@ public Val receive(String function, String overload, Val... args) {
   /** Size implements traits.Sizer.Size. */
   @Override
   public Val size() {
-    return intOf(s.length());
+    return intOf(s.codePointCount(0, s.length()));
   }
 
   /** Type implements ref.Val.Type. */

core/src/test/java/org/projectnessie/cel/common/types/StringTest.java

@@ -217,4 +217,10 @@ void stringSize() {
     assertThat(stringOf("hello world").size()).isEqualTo(intOf(11));
     assertThat(stringOf("\u65e5\u672c\u8a9e").size()).isEqualTo(intOf(3));
   }
+
+  @Test
+  void stringSizeEmoji() {
+    assertThat(stringOf("").size()).isSameAs(IntZero);
+    assertThat(stringOf("\uD83D\uDE05\uD83D\uDE04\uD83D\uDC7E").size()).isEqualTo(intOf(3));
+  }
 }