Always return an array for fields when using QueryBuilder

Author: msargentibm

CHANGES.md

@@ -1,5 +1,6 @@
 # Unreleased
 - [UPGRADED] Optional OkHttp dependency to version 3.12.2.
+- [FIXED] Create an array of strings for QueryBuilder.fields() when a single field is provided.
 
 # 2.17.0 (2019-05-23)
 - [NEW] Added `com.cloudant.client.api.model.DbInfo#getDocDelCountLong()` to return

cloudant-client/src/main/java/com/cloudant/client/api/query/QueryBuilder.java

@@ -191,7 +191,7 @@ public QueryBuilder useIndex(String designDocument, String indexName) {
      * @return String representation of query.
      */
     public String build() {
-        String fieldsString = this.fields == null ? null : Helpers.quote(this.fields);
+        String fieldsString = this.fields == null ? null : Helpers.quote(this.fields, true);
         String sortString = this.sort == null ? null : quoteSort(this.sort);
         String limitString = this.limit == null ? null : Helpers.quote(this.limit);
         String skipString = this.skip == null ? null : Helpers.quote(this.skip);

cloudant-client/src/test/java/com/cloudant/tests/QueryTests.java

@@ -251,6 +251,14 @@ public void complexSelector2() {
                 "{\"$eq\": \"de Vito\"}}, {\"Year\": {\"$eq\": 2001}}]}]}}", qb.build());
     }
 
+    // fields must always be an array of strings, even with a single field provided
+    @Test
+    public void basicSelector1WithField() {
+        QueryBuilder qb = new QueryBuilder(eq("director", "Lars von Trier")).fields("_id");
+        Assertions.assertEquals("{\"selector\": {\"director\": {\"$eq\": \"Lars von Trier\"}}, " +
+                                        "\"fields\": [\"_id\"]}", qb.build());
+    }
+
     // "Selector basics"
     @Test
     public void basicSelector1WithFields() {