Add support for reusing a snippet to document common elements

This commit updates all of the Snippet implementations that take one
or more descriptors to provide an and method that can be used to
create a new Snippet that has additional descriptors.

Closes gh-168

spring-restdocs-core/src/test/java/org/springframework/restdocs/headers/RequestHeadersSnippetTests.java

@@ -143,4 +143,27 @@ public class RequestHeadersSnippetTests extends AbstractSnippetTests {
 										.header("Accept", "*/*").build());
 	}
 
+	@Test
+	public void additionalDescriptors() throws IOException {
+		this.snippet.expectRequestHeaders("additional-descriptors")
+				.withContents(tableWithHeader("Name", "Description").row("X-Test", "one")
+						.row("Accept", "two").row("Accept-Encoding", "three")
+						.row("Accept-Language", "four").row("Cache-Control", "five")
+						.row("Connection", "six"));
+		HeaderDocumentation
+				.requestHeaders(headerWithName("X-Test").description("one"),
+						headerWithName("Accept").description("two"),
+						headerWithName("Accept-Encoding").description("three"),
+						headerWithName("Accept-Language").description("four"))
+				.and(headerWithName("Cache-Control").description("five"),
+						headerWithName("Connection").description("six"))
+				.document(operationBuilder("additional-descriptors")
+						.request("http://localhost").header("X-Test", "test")
+						.header("Accept", "*/*")
+						.header("Accept-Encoding", "gzip, deflate")
+						.header("Accept-Language", "en-US,en;q=0.5")
+						.header("Cache-Control", "max-age=0")
+						.header("Connection", "keep-alive").build());
+	}
+
 }

spring-restdocs-core/src/test/java/org/springframework/restdocs/headers/ResponseHeadersSnippetTests.java

@@ -133,4 +133,25 @@ public class ResponseHeadersSnippetTests extends AbstractSnippetTests {
 										.header("Etag", "lskjadldj3ii32l2ij23").build());
 	}
 
+	@Test
+	public void additionalDescriptors() throws IOException {
+		this.snippet.expectResponseHeaders("additional-descriptors")
+				.withContents(tableWithHeader("Name", "Description").row("X-Test", "one")
+						.row("Content-Type", "two").row("Etag", "three")
+						.row("Cache-Control", "five").row("Vary", "six"));
+		HeaderDocumentation
+				.responseHeaders(headerWithName("X-Test").description("one"),
+						headerWithName("Content-Type").description("two"),
+						headerWithName("Etag").description("three"))
+				.and(headerWithName("Cache-Control").description("five"),
+						headerWithName("Vary")
+								.description("six"))
+				.document(operationBuilder("additional-descriptors").response()
+						.header("X-Test", "test")
+						.header("Content-Type", "application/json")
+						.header("Etag", "lskjadldj3ii32l2ij23")
+						.header("Cache-Control", "max-age=0").header("Vary", "User-Agent")
+						.build());
+	}
+
 }

spring-restdocs-core/src/test/java/org/springframework/restdocs/hypermedia/LinksSnippetTests.java

@@ -132,4 +132,16 @@ public class LinksSnippetTests extends AbstractSnippetTests {
 												.build());
 	}
 
+	@Test
+	public void additionalDescriptors() throws IOException {
+		this.snippet.expectLinks("additional-descriptors")
+				.withContents(tableWithHeader("Relation", "Description").row("a", "one")
+						.row("b", "two"));
+		HypermediaDocumentation
+				.links(new StubLinkExtractor().withLinks(new Link("a", "alpha"),
+						new Link("b", "bravo")),
+				new LinkDescriptor("a").description("one"))
+				.and(new LinkDescriptor("b").description("two"))
+				.document(operationBuilder("additional-descriptors").build());
+	}
 }

spring-restdocs-core/src/test/java/org/springframework/restdocs/payload/RequestFieldsSnippetTests.java

@@ -160,4 +160,20 @@ public class RequestFieldsSnippetTests extends AbstractSnippetTests {
 								.build());
 	}
 
+	@Test
+	public void additionalDescriptors() throws IOException {
+		this.snippet.expectRequestFields("additional-descriptors")
+				.withContents(tableWithHeader("Path", "Type", "Description")
+						.row("a.b", "Number", "one").row("a.c", "String", "two")
+						.row("a", "Object", "three"));
+
+		PayloadDocumentation
+				.requestFields(fieldWithPath("a.b").description("one"),
+						fieldWithPath("a.c").description("two"))
+				.and(fieldWithPath("a").description("three"))
+				.document(operationBuilder("additional-descriptors")
+						.request("http://localhost")
+						.content("{\"a\": {\"b\": 5, \"c\": \"charlie\"}}").build());
+	}
+
 }

spring-restdocs-core/src/test/java/org/springframework/restdocs/payload/ResponseFieldsSnippetTests.java

@@ -211,4 +211,25 @@ public class ResponseFieldsSnippetTests extends AbstractSnippetTests {
 								.build());
 	}
 
+	@Test
+	public void additionalDescriptors() throws IOException {
+		this.snippet.expectResponseFields("additional-descriptors")
+				.withContents(tableWithHeader("Path", "Type", "Description")
+						.row("id", "Number", "one").row("date", "String", "two")
+						.row("assets", "Array", "three").row("assets[]", "Object", "four")
+						.row("assets[].id", "Number", "five")
+						.row("assets[].name", "String", "six"));
+		PayloadDocumentation
+				.responseFields(fieldWithPath("id").description("one"),
+						fieldWithPath("date").description("two"),
+						fieldWithPath("assets").description("three"))
+				.and(fieldWithPath("assets[]").description("four"),
+						fieldWithPath("assets[].id").description("five"),
+						fieldWithPath("assets[].name").description("six"))
+				.document(operationBuilder("additional-descriptors").response()
+						.content("{\"id\": 67,\"date\": \"2015-01-20\",\"assets\":"
+								+ " [{\"id\":356,\"name\": \"sample\"}]}")
+						.build());
+	}
+
 }

spring-restdocs-core/src/test/java/org/springframework/restdocs/request/PathParametersSnippetTests.java

@@ -133,6 +133,19 @@ public class PathParametersSnippetTests extends AbstractSnippetTests {
 										.build());
 	}
 
+	@Test
+	public void additionalDescriptors() throws IOException {
+		this.snippet.expectPathParameters("additional-descriptors").withContents(
+				tableWithTitleAndHeader(getTitle(), "Parameter", "Description")
+						.row("a", "one").row("b", "two"));
+		RequestDocumentation.pathParameters(parameterWithName("a").description("one"))
+				.and(parameterWithName("b").description("two"))
+				.document(operationBuilder("additional-descriptors")
+						.attribute(RestDocumentationGenerator.ATTRIBUTE_NAME_URL_TEMPLATE,
+								"/{a}/{b}")
+						.build());
+	}
+
 	private String getTitle() {
 		return this.templateFormat == TemplateFormats.asciidoctor() ? "/{a}/{b}"
 				: "`/{a}/{b}`";

spring-restdocs-core/src/test/java/org/springframework/restdocs/request/RequestParametersSnippetTests.java

@@ -128,4 +128,16 @@ public class RequestParametersSnippetTests extends AbstractSnippetTests {
 												.build());
 	}
 
+	@Test
+	public void additionalDescriptors() throws IOException {
+		this.snippet.expectRequestParameters("additional-descriptors")
+				.withContents(tableWithHeader("Parameter", "Description").row("a", "one")
+						.row("b", "two"));
+		RequestDocumentation.requestParameters(parameterWithName("a").description("one"))
+				.and(parameterWithName("b").description("two"))
+				.document(operationBuilder("additional-descriptors")
+						.request("http://localhost").param("a", "bravo")
+						.param("b", "bravo").build());
+	}
+
 }