Allow digits in URL schemes per RFC

src/main/java/org/scribe/utils/Preconditions.java

@@ -12,7 +12,9 @@ import org.scribe.model.OAuthConstants;
 public class Preconditions
 {
   private static final String DEFAULT_MESSAGE = "Received an invalid parameter";
-  private static final Pattern URL_PATTERN = Pattern.compile("[a-zA-Z_-]+://\\S+");
+  
+  // scheme = alpha *( alpha | digit | "+" | "-" | "." )
+  private static final Pattern URL_PATTERN = Pattern.compile("^[a-zA-Z][a-zA-Z0-9+.-]*://\\S+");
 
   /**
    * Checks that an object is not null.

src/test/java/org/scribe/utils/PreconditionsTest.java

@@ -43,16 +43,25 @@ public class PreconditionsTest
     Preconditions.checkValidUrl(null, ERROR_MSG);
   }
   
+  @Test
   public void shouldAllowValidUrls()
   {
     Preconditions.checkValidUrl("http://www.example.com", ERROR_MSG);
   }
   
+  @Test
   public void shouldAllowSSLUrls()
   {
     Preconditions.checkValidUrl("https://www.example.com", ERROR_MSG);
   }
+
+  @Test
+  public void shouldAllowSpecialCharsInScheme() 
+  {
+    Preconditions.checkValidUrl("custom+9.3-1://www.example.com", ERROR_MSG);
+  }
   
+  @Test
   public void shouldAllowNonStandarProtocolsForAndroid()
   {
     Preconditions.checkValidUrl("x-url-custom://www.example.com", ERROR_MSG);
@@ -64,6 +73,13 @@ public class PreconditionsTest
     Preconditions.checkValidUrl("$weird*://www.example.com", ERROR_MSG);
   }
   
+  @Test(expected = IllegalArgumentException.class)
+  public void shouldNotAllowUnderscoreInScheme()
+  {
+    Preconditions.checkValidUrl("http_custom://www.example.com", ERROR_MSG);
+  }
+  
+  @Test
   public void shouldAllowOutOfBandAsValidCallbackValue()
   {
     Preconditions.checkValidOAuthCallback("oob", ERROR_MSG);