fix issue #786 and add test case (#801)

Author: sdww0

json-path/src/main/java/com/jayway/jsonpath/internal/path/FunctionPathToken.java

@@ -1,5 +1,6 @@
 package com.jayway.jsonpath.internal.path;
 
+import com.jayway.jsonpath.internal.Path;
 import com.jayway.jsonpath.internal.PathRef;
 import com.jayway.jsonpath.internal.function.Parameter;
 import com.jayway.jsonpath.internal.function.PathFunction;
@@ -39,11 +40,29 @@ public void evaluate(String currentPath, PathRef parent, Object model, Evaluatio
         evaluateParameters(currentPath, parent, model, ctx);
         Object result = pathFunction.invoke(currentPath, parent, model, ctx, functionParams);
         ctx.addResult(currentPath + "." + functionName, parent, result);
+        cleanWildcardPathToken();
         if (!isLeaf()) {
             next().evaluate(currentPath, parent, result, ctx);
         }
     }
 
+    private void cleanWildcardPathToken() {
+        if (null != functionParams && functionParams.size() > 0) {
+            Path path = functionParams.get(0).getPath();
+            if (null != path && !path.isFunctionPath() && path instanceof CompiledPath) {
+                RootPathToken root = ((CompiledPath) path).getRoot();
+                PathToken tail = root.getNext();
+                while (null != tail && null != tail.getNext() ) {
+                    if(tail.getNext() instanceof WildcardPathToken){
+                        tail.setNext(tail.getNext().getNext());
+                        break;
+                    }
+                    tail = tail.getNext();
+                }
+            }
+        }
+    }
+
     private void evaluateParameters(String currentPath, PathRef parent, Object model, EvaluationContextImpl ctx) {
 
         if (null != functionParams) {

json-path/src/test/java/com/jayway/jsonpath/Issue_786.java

@@ -0,0 +1,23 @@
+package com.jayway.jsonpath;
+
+import org.junit.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * test for issue 786
+ */
+public class Issue_786 extends BaseTest{
+
+    @Test
+    public void test(){
+        assertThat(bookLength()).describedAs("First run").isEqualTo(4);
+        assertThat(bookLength()).describedAs("Second run").isEqualTo(4);
+        assertThat(bookLength()).describedAs("Third run").isEqualTo(4);
+    }
+
+    private int bookLength() {
+        return JsonPath.read(JSON_DOCUMENT, "$..book.length()");
+    }
+
+}