Escape supplemental characters correctly

CHANGES

@@ -49,6 +49,9 @@ Release 1.16.2 [PENDING]
     ASCII.
     <https://github.com/jhy/jsoup/issues/1952>
 
+  * Bugfix: in Jsoup.connect(url), strings containing supplemental characters (e.g. emoji) were not URL escaped
+    correctly.
+
   * Bugfix: in Jsoup.connect(url), the ConstrainableInputStream would clear Thread interrupts when reading the body.
     This precluded callers from spawning a thread, running a number of requests for a length of time, then joining that
     thread after interrupting it.

src/main/java/org/jsoup/helper/UrlBuilder.java

@@ -90,6 +90,7 @@ private static void appendToAscii(String s, boolean spaceAsPlus, StringBuilder s
             } else if (c > 127) { // out of ascii range
                 sb.append(URLEncoder.encode(new String(Character.toChars(c)), UTF_8.name()));
                 // ^^ is a bit heavy-handed - if perf critical, we could optimize
+                if (Character.charCount(c) == 2) i++; // advance past supplemental
             } else {
                 sb.append((char) c);
             }

src/test/java/org/jsoup/helper/HttpConnectionTest.java

@@ -260,6 +260,12 @@ public void caseInsensitiveHeaders(Locale locale) {
         assertEquals("https://test.com/foo%20bar/%5BOne%5D?q=white+space#frag", url2.toExternalForm());
     }
 
+    @Test public void encodeUrlSupplementary() throws MalformedURLException {
+        URL url1 = new URL("https://example.com/tools/test💩.html"); // = "/tools/test\uD83D\uDCA9.html"
+        URL url2 = new UrlBuilder(url1).build();
+        assertEquals("https://example.com/tools/test%F0%9F%92%A9.html", url2.toExternalForm());
+    }
+
     @Test void encodedUrlDoesntDoubleEncode() throws MalformedURLException {
         URL url1 = new URL("https://test.com/foo%20bar/%5BOne%5D?q=white+space#frag%20ment");
         URL url2 = new UrlBuilder(url1).build();