REST: Add newline to response when using pretty flag

closes #3748
relates to #3422

src/main/java/org/elasticsearch/common/xcontent/XContentBuilder.java

@@ -109,6 +109,11 @@ public final class XContentBuilder implements BytesStream {
         return this;
     }
 
+    public XContentBuilder lfAtEnd() {
+        generator.usePrintLineFeedAtEnd();
+        return this;
+    }
+
     public XContentBuilder humanReadable(boolean humanReadable) {
         this.humanReadable = humanReadable;
         return this;

src/main/java/org/elasticsearch/common/xcontent/XContentGenerator.java

@@ -34,6 +34,8 @@ public interface XContentGenerator {
 
     void usePrettyPrint();
 
+    void usePrintLineFeedAtEnd();
+
     void writeStartArray() throws IOException;
 
     void writeEndArray() throws IOException;

src/main/java/org/elasticsearch/common/xcontent/json/JsonXContentGenerator.java

@@ -20,6 +20,7 @@
 package org.elasticsearch.common.xcontent.json;
 
 import com.fasterxml.jackson.core.JsonGenerator;
+import com.fasterxml.jackson.core.io.SerializedString;
 import org.elasticsearch.common.bytes.BytesReference;
 import org.elasticsearch.common.io.Streams;
 import org.elasticsearch.common.xcontent.*;
@@ -34,6 +35,7 @@ import java.io.OutputStream;
 public class JsonXContentGenerator implements XContentGenerator {
 
     protected final JsonGenerator generator;
+    private boolean writeLineFeedAtEnd;
 
     public JsonXContentGenerator(JsonGenerator generator) {
         this.generator = generator;
@@ -49,6 +51,11 @@ public class JsonXContentGenerator implements XContentGenerator {
         generator.useDefaultPrettyPrinter();
     }
 
+    @Override
+    public void usePrintLineFeedAtEnd() {
+        writeLineFeedAtEnd = true;
+    }
+
     @Override
     public void writeStartArray() throws IOException {
         generator.writeStartArray();
@@ -320,6 +327,12 @@ public class JsonXContentGenerator implements XContentGenerator {
 
     @Override
     public void close() throws IOException {
+        if (writeLineFeedAtEnd) {
+            flush();
+            generator.writeRaw(LF);
+        }
         generator.close();
     }
+
+    private static final SerializedString LF = new SerializedString("\n");
 }

src/main/java/org/elasticsearch/common/xcontent/smile/SmileXContentGenerator.java

@@ -43,6 +43,11 @@ public class SmileXContentGenerator extends JsonXContentGenerator {
         return XContentType.SMILE;
     }
 
+    @Override
+    public void usePrintLineFeedAtEnd() {
+        // nothing here
+    }
+
     @Override
     public void writeRawField(String fieldName, InputStream content, OutputStream bos) throws IOException {
         writeFieldName(fieldName);

src/main/java/org/elasticsearch/common/xcontent/yaml/YamlXContentGenerator.java

@@ -43,6 +43,11 @@ public class YamlXContentGenerator extends JsonXContentGenerator {
         return XContentType.YAML;
     }
 
+    @Override
+    public void usePrintLineFeedAtEnd() {
+        // nothing here
+    }
+
     @Override
     public void writeRawField(String fieldName, InputStream content, OutputStream bos) throws IOException {
         writeFieldName(fieldName);

src/main/java/org/elasticsearch/rest/action/support/RestXContentBuilder.java

@@ -55,7 +55,7 @@ public class RestXContentBuilder {
         }
         XContentBuilder builder = new XContentBuilder(XContentFactory.xContent(contentType), new BytesStreamOutput());
         if (request.paramAsBoolean("pretty", false)) {
-            builder.prettyPrint();
+            builder.prettyPrint().lfAtEnd();
         }
 
         builder.humanReadable(request.paramAsBoolean("human", builder.humanReadable()));