Fix inheritance provider chaining

Previously, each provider would be consulted until a matching parent is
found. This is incorrect and caused spurious warnings with --live
(jar + runtime inheritance), as unmatched classes in the jar would fall
through to the runtime inheritance provider.

Now once a provider returns non-null, no other providers are checked.
null indicates the provider knows nothing about the class and should
ask elsewhere, non-null indicates a definitive list of inheritance
(extends/implements list) classes. Should be slightly faster, too.

src/main/java/net/md_5/specialsource/IInheritanceProvider.java

@@ -36,7 +36,7 @@ public interface IInheritanceProvider {
      * Get the superclass and implemented interfaces of a class
      *
      * @param className
-     * @return
+     * @return List of interfaces, or null if no information is available and other providers should be checked
      */
     List<String> getParents(String className);
 }

src/main/java/net/md_5/specialsource/JarInheritanceProvider.java

@@ -49,14 +49,18 @@ public class JarInheritanceProvider implements IInheritanceProvider {
     @Override
     @SuppressWarnings("unchecked") // Saddens me to see ASM strip vital info like that
     public List<String> getParents(String owner) {
-        List<String> parents = new ArrayList<String>();
         ClassNode node = self.getNode(owner);
-        if (node != null) {
-            for (String iface : (List<String>) node.interfaces) {
-                parents.add(iface);
-            }
-            parents.add(node.superName);
+        if (node == null) {
+            return null;
         }
+
+        List<String> parents = new ArrayList<String>();
+
+        for (String iface : (List<String>) node.interfaces) {
+            parents.add(iface);
+        }
+        parents.add(node.superName);
+
         return parents;
     }
 }

src/main/java/net/md_5/specialsource/JarRemapper.java

@@ -97,12 +97,19 @@ public class JarRemapper extends Remapper {
 
         String mapped = map.get(key);
         if (mapped == null) {
+            // ask each provider for inheritance information on the class, until one responds
             for (IInheritanceProvider inheritanceProvider : inheritanceProviders) {
-                for (String parent : inheritanceProvider.getParents(owner)) {
-                    mapped = tryClimb(map, type, parent, name);
-                    if (mapped != null) {
-                        return mapped;
+                List<String> parents = inheritanceProvider.getParents(owner);
+
+                if (parents != null) {
+                    // climb the inheritance tree
+                    for (String parent : parents) {
+                        mapped = tryClimb(map, type, parent, name);
+                        if (mapped != null) {
+                            return mapped;
+                        }
                     }
+                    break;
                 }
             }
         }

src/main/java/net/md_5/specialsource/RuntimeInheritanceProvider.java

@@ -47,7 +47,7 @@ public class RuntimeInheritanceProvider implements IInheritanceProvider {
             //clazz = Class.forName(toSourceName(sourceClassName)); // runs static initializers - avoid!
         } catch (Throwable t) {
             SpecialSource.log("RuntimeInheritanceProvider failed: " + t);
-            return parents;
+            return null;
         }
 
         for (Class iface : clazz.getInterfaces()) {