Ensure that additional snippets are only called once

Previously, when additional snippets were added to a
RestDocumentationResultHandler, those snippets would then be called
for every subsequent call to handle(MvcResult). This is problematic as
the snippets and their configuration are specific to a particular
MvcResult that is being documented.

This commit updates RestDocumentationResultHandler so that it clears
its additional snippets each time handle(MvcResult) is called.

Closes gh-243

spring-restdocs-mockmvc/src/main/java/org/springframework/restdocs/mockmvc/RestDocumentationResultHandler.java

@@ -44,6 +44,8 @@ import static org.springframework.restdocs.mockmvc.IterableEnumeration.iterable;
  */
 public class RestDocumentationResultHandler implements ResultHandler {
 
+	private final List<Snippet> additionalSnippets;
+
 	private final String identifier;
 
 	private final OperationRequestPreprocessor requestPreprocessor;
@@ -80,6 +82,7 @@ public class RestDocumentationResultHandler implements ResultHandler {
 		this.requestPreprocessor = requestPreprocessor;
 		this.responsePreprocessor = responsePreprocessor;
 		this.snippets = new ArrayList<>(Arrays.asList(snippets));
+		this.additionalSnippets = new ArrayList<>();
 	}
 
 	@Override
@@ -110,7 +113,7 @@ public class RestDocumentationResultHandler implements ResultHandler {
 	 * @return this {@code ResultDocumentationResultHandler}
 	 */
 	public RestDocumentationResultHandler snippets(Snippet... snippets) {
-		this.snippets.addAll(Arrays.asList(snippets));
+		this.additionalSnippets.addAll(Arrays.asList(snippets));
 		return this;
 	}
 
@@ -120,6 +123,8 @@ public class RestDocumentationResultHandler implements ResultHandler {
 				(List<Snippet>) result.getRequest().getAttribute(
 						"org.springframework.restdocs.mockmvc.defaultSnippets"));
 		combinedSnippets.addAll(this.snippets);
+		combinedSnippets.addAll(this.additionalSnippets);
+		this.additionalSnippets.clear();
 		return combinedSnippets;
 	}
 

spring-restdocs-mockmvc/src/test/java/org/springframework/restdocs/mockmvc/RestDocumentationResultHandlerTests.java

@@ -0,0 +1,64 @@
+/*
+ * Copyright 2014-2016 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.restdocs.mockmvc;
+
+import java.util.Arrays;
+
+import org.junit.Test;
+import org.mockito.Matchers;
+
+import org.springframework.mock.web.MockHttpServletRequest;
+import org.springframework.mock.web.MockHttpServletResponse;
+import org.springframework.restdocs.operation.Operation;
+import org.springframework.restdocs.snippet.Snippet;
+import org.springframework.test.web.servlet.MvcResult;
+
+import static org.mockito.BDDMockito.given;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+
+/**
+ * Tests for {@link RestDocumentationResultHandler}.
+ *
+ * @author Andy Wilkinson
+ */
+public class RestDocumentationResultHandlerTests {
+
+	@Test
+	public void additionalSnippetsAreOnlyCalledOnce() throws Exception {
+		Snippet snippet = mock(Snippet.class);
+		RestDocumentationResultHandler resultHandler = new RestDocumentationResultHandler(
+				"test", snippet);
+		Snippet defaultSnippet = mock(Snippet.class);
+		Snippet additionalSnippet = mock(Snippet.class);
+		resultHandler.snippets(additionalSnippet);
+		MvcResult result = mock(MvcResult.class);
+		MockHttpServletRequest request = new MockHttpServletRequest("GET",
+				"http://localhost");
+		request.setAttribute("org.springframework.restdocs.mockmvc.defaultSnippets",
+				Arrays.asList(defaultSnippet));
+		given(result.getRequest()).willReturn(request);
+		given(result.getResponse()).willReturn(new MockHttpServletResponse());
+		resultHandler.handle(result);
+		resultHandler.handle(result);
+		verify(defaultSnippet, times(2)).document(Matchers.any(Operation.class));
+		verify(snippet, times(2)).document(Matchers.any(Operation.class));
+		verify(additionalSnippet, times(1)).document(Matchers.any(Operation.class));
+	}
+
+}