absUrl now supports already abs URLs, even when there's no defined st…

…ream handler

Fixes #1610

CHANGES

@@ -4,6 +4,10 @@ jsoup changelog
   * Improvement: support Pattern.quote \Q and \E escapes in the selector regex matchers.
     <https://github.com/jhy/jsoup/pull/1536>
 
+  * Improvement: Element.absUrl() now supports tel: URLs, and other URLs that are already absolute but that Java does
+    not have input stream handlers for.
+    <https://github.com/jhy/jsoup/issues/1610>
+
   * Bugfix: when serializing output, escape characters that are in the < 0x20 range. This improves XML output
     compatibility, and makes HTML output with these characters easier to read (as they're otherwise invisible).
     <https://github.com/jhy/jsoup/issues/1556>

src/main/java/org/jsoup/internal/StringUtil.java

@@ -299,9 +299,11 @@ public static String resolve(final String baseUrl, final String relUrl) {
             }
             return resolve(base, relUrl).toExternalForm();
         } catch (MalformedURLException e) {
-            return "";
+            // it may still be valid, just that Java doesn't have a registered stream handler for it, e.g. tel:
+            return validUriScheme.matcher(relUrl).find() ? relUrl : "";
         }
     }
+    private static final Pattern validUriScheme = Pattern.compile("^[a-zA-Z][a-zA-Z0-9+-.]*:");
 
     private static final ThreadLocal<Stack<StringBuilder>> threadLocalBuilders = new ThreadLocal<Stack<StringBuilder>>() {
         @Override

src/main/java/org/jsoup/nodes/Element.java

@@ -82,7 +82,7 @@ public Element(Tag tag, @Nullable String baseUri, @Nullable Attributes attribute
      * @param baseUri the base URI of this element. Optional, and will inherit from its parent, if any.
      * @see Tag#valueOf(String, ParseSettings)
      */
-    public Element(Tag tag, String baseUri) {
+    public Element(Tag tag, @Nullable String baseUri) {
         this(tag, baseUri, null);
     }
 

src/test/java/org/jsoup/nodes/NodeTest.java

@@ -3,6 +3,7 @@
 import org.jsoup.Jsoup;
 import org.jsoup.TextUtil;
 import org.jsoup.parser.Tag;
+import org.jsoup.select.Elements;
 import org.jsoup.select.NodeVisitor;
 import org.junit.jupiter.api.Test;
 
@@ -132,6 +133,21 @@ public void handlesAbsOnProtocolessAbsoluteUris() {
         assertEquals("http://example.com/one/two.html", a1.absUrl("href"));
     }
 
+    @Test public void handlesAbsOnUnknownProtocols() {
+        // https://github.com/jhy/jsoup/issues/1610
+        // URL would throw on unknown protocol tel: as no stream handler is registered
+
+        String[] urls = {"mailto:example@example.com", "tel:867-5309"}; // mail has a handler, tel doesn't
+        for (String url : urls) {
+            Attributes attr = new Attributes().put("href", url);
+            Element noBase = new Element(Tag.valueOf("a"), null, attr);
+            assertEquals(url, noBase.absUrl("href"));
+
+            Element withBase = new Element(Tag.valueOf("a"), "http://example.com/", attr);
+            assertEquals(url, withBase.absUrl("href"));
+        }
+    }
+
     @Test public void testRemove() {
         Document doc = Jsoup.parse("<p>One <span>two</span> three</p>");
         Element p = doc.select("p").first();