Fix exception when replicating with CouchDB 2.3 (#594)

Fixed purge_seq to return a String object when replicating with CouchDB 2.3 databases
- Define purge_seq as String as required by CouchDB 2.3
- Add test checking that long purge_seq is correctly deserialized into String

Author: jjrodrig

CHANGES.md

@@ -2,7 +2,8 @@
 - [NEW] `Database` methods `read`, `contains`, `create`, and `delete` now accept local
   (non-replicating documents). These documents must have their document ID prefixed with `_local/`
   and must have their revision ID set to `null` (where applicable).
-  
+- [FIXED] Fixed purge_seq to return a String object when replicating with CouchDB 2.3 databases. 
+     
 # 2.3.0 (2018-08-14)
 - [NEW] Added API for specifying a list of document IDs in the filtered pull replicator.
 - [IMPROVED] Forced a TLS1.2 `SSLSocketFactory` where possible on Android API versions < 20 (it is

cloudant-sync-datastore-core/src/main/java/com/cloudant/sync/internal/mazha/CouchDbInfo.java

@@ -40,7 +40,7 @@ public class CouchDbInfo {
 	private Object updateSeq;
 
 	@JsonProperty("purge_seq")
-	private long purgeSeq;
+	private String purgeSeq;
 
 	@JsonProperty("compact_running")
 	private boolean compactRunning;
@@ -73,7 +73,7 @@ public Object getUpdateSeq() {
 		return updateSeq;
 	}
 
-	public long getPurgeSeq() {
+	public String getPurgeSeq() {
 		return purgeSeq;
 	}
 

cloudant-sync-datastore-core/src/test/java/com/cloudant/sync/util/JSONUtilsTest.java

@@ -16,17 +16,24 @@
 
 package com.cloudant.sync.util;
 
-import com.cloudant.sync.internal.util.JSONUtils;
+import com.cloudant.sync.internal.mazha.CouchDbInfo;
 import com.cloudant.sync.internal.replication.Foo;
-import org.junit.Assert;
+import com.cloudant.sync.internal.util.JSONUtils;
+import com.fasterxml.jackson.core.type.TypeReference;
+
 import org.apache.commons.io.FileUtils;
+import static org.hamcrest.CoreMatchers.is;
+import org.junit.Assert;
 import org.junit.Test;
 
+import java.io.File;
+import java.io.FileReader;
 import java.io.IOException;
 import java.util.Arrays;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.regex.Matcher;
 
 public class JSONUtilsTest {
 
@@ -149,6 +156,16 @@ public void deserialize_complexDocumentWith_correctlySerializedToMap() throws Ex
         Assert.assertEquals(Integer.valueOf(40), breakfast.get("Duration"));
     }
 
+    @Test
+    public void deserialize_CouchDBInfo_purgeSeq_from_long() throws Exception {
+        File dbinfoData = TestUtils.loadFixture("fixture/dbinfo-pre23.json");
+        CouchDbInfo deserialized = JSONUtils.fromJson(new FileReader(dbinfoData), new
+                TypeReference<CouchDbInfo>() {
+        });
+        Long purgeSeq = Long.valueOf(deserialized.getPurgeSeq());
+        Assert.assertThat(purgeSeq, is(0l));
+    }
+
     private byte[] readJsonDataFromFile(String filename) throws IOException {
         byte[] data = FileUtils.readFileToByteArray(TestUtils.loadFixture(filename));
         return data;

fixture/dbinfo-pre23.json

@@ -0,0 +1,20 @@
+{
+  "db_name": "test",
+  "update_seq": "4-g1AAAAFTeJzLYWBg4MhgTmEQTM4vTc5ISXLIyU9OzMnILy7JAUoxJTIkyf___z8rkQGPoiQFIJlkD1bHiE-dA0hdPFgdEz51CSB19QTtzWMBkgwNQAqodD4xahdA1O4nRu0BiNr7-P0EUfsAohbk3iwA10dvMg",
+  "sizes": {
+    "file": 161030,
+    "external": 112978,
+    "active": 113762
+  },
+  "purge_seq": 0,
+  "other": {
+    "data_size": 112978
+  },
+  "doc_del_count": 0,
+  "doc_count": 3,
+  "disk_size": 161030,
+  "disk_format_version": 6,
+  "data_size": 113762,
+  "compact_running": false,
+  "instance_start_time": "0"
+}