Make MustacheCustomContext a Mustache inner interface.

This matches the style of all the other extension points.

src/main/java/com/samskivert/mustache/BasicCollector.java

@@ -35,7 +35,7 @@ public abstract class BasicCollector implements Mustache.Collector
     }
 
     public Mustache.VariableFetcher createFetcher (Object ctx, String name) {
-        if (ctx instanceof MustacheCustomContext) return CUSTOM_FETCHER;
+        if (ctx instanceof Mustache.CustomContext) return CUSTOM_FETCHER;
         if (ctx instanceof Map<?,?>) return MAP_FETCHER;
 
         // if the name looks like a number, potentially use one of our 'indexing' fetchers
@@ -68,7 +68,7 @@ public abstract class BasicCollector implements Mustache.Collector
 
     protected static final Mustache.VariableFetcher CUSTOM_FETCHER = new Mustache.VariableFetcher() {
         public Object get (Object ctx, String name) throws Exception {
-            MustacheCustomContext custom = (MustacheCustomContext)ctx;
+            Mustache.CustomContext custom = (Mustache.CustomContext)ctx;
             Object val = custom.get(name);
             return val == null ? Template.NO_FETCHER_FOUND : val;
         }

src/main/java/com/samskivert/mustache/DefaultCollector.java

@@ -4,12 +4,9 @@
 
 package com.samskivert.mustache;
 
-import java.lang.reflect.Array;
 import java.lang.reflect.Field;
 import java.lang.reflect.Method;
 
-import java.util.AbstractList;
-import java.util.Iterator;
 import java.util.LinkedHashSet;
 import java.util.Map;
 import java.util.Set;

src/main/java/com/samskivert/mustache/Mustache.java

@@ -324,6 +324,21 @@ public class Mustache {
         <K,V> Map<K,V> createFetcherCache ();
     }
 
+    /**
+     * Provides a means to implement custom logic for variable lookup. If a context object
+     * implements this interface, its {@code get} method will be used to look up variables instead
+     * of the usual methods.
+     *
+     * This is simpler than having a context implement {@link Map} which would require that it also
+     * support the {@link Map#entrySet} method for iteration. A {@code CustomContext} object cannot
+     * be used for a list section.
+     */
+    public interface CustomContext {
+
+        /** Fetches the value of a variable named {@code name}. */
+        Object get (String name) throws Exception;
+    }
+
     /** Used to visit the tags in a template without executing it. */
     public interface Visitor {
 

src/main/java/com/samskivert/mustache/MustacheCustomContext.java

@@ -1,8 +0,0 @@
-package com.samskivert.mustache;
-
-/**
- * Provides a simple interface for callers to implement their own logic for contextual values.
- */
-public interface MustacheCustomContext {
-    Object get(String name) throws Exception;
-}

src/test/java/com/samskivert/mustache/MustacheTest.java

@@ -45,8 +45,8 @@ public class MustacheTest extends SharedTests
         });
     }
 
-    @Test public void testMustacheCustomContext() {
-        test("bar", "{{foo}}", new MustacheCustomContext() {
+    @Test public void testCustomContext() {
+        test("bar", "{{foo}}", new Mustache.CustomContext() {
             @Override
             public Object get(String name) {
                 return "foo".equals(name) ? "bar" : null;