Add ResultEmpty class

This allows for the creation of synthetic empty result sets

lib/Db/AbstractResult.php

@@ -17,15 +17,19 @@ abstract class AbstractResult implements Result {
             $out = array_shift($this->cur);
             $this->next();
             return $out;
-        }
+        } else {
-        $this->next();
             return null;
         }
+    }
 
     public function getRow() {
-        $out = ($this->valid() ? $this->cur : null);
+        if ($this->valid()) {
+            $out = $this->cur;
             $this->next();
             return $out;
+        } else {
+            return null;
+        }
     }
 
     public function getAll(): array {

lib/Db/ResultEmpty.php

@@ -0,0 +1,25 @@
+<?php
+/** @license MIT
+ * Copyright 2017 J. King, Dustin Wilson et al.
+ * See LICENSE and AUTHORS files for details */
+
+declare(strict_types=1);
+namespace JKingWeb\Arsse\Db;
+
+use JKingWeb\Arsse\Db\Exception;
+
+class ResultEmpty extends AbstractResult {
+    public function changes() {
+        return 0;
+    }
+
+    public function lastId() {
+        return 0;
+    }
+
+    // PHP iterator methods
+
+    public function valid() {
+        return false;
+    }
+}

tests/Db/TestResultEmpty.php

@@ -0,0 +1,37 @@
+<?php
+declare(strict_types=1);
+namespace JKingWeb\Arsse;
+
+/** @covers \JKingWeb\Arsse\Db\ResultEmpty<extended> */
+class TestResultEmpty extends Test\AbstractTest {
+
+    public function testGetChangeCountAndLastInsertId() {
+        $r = new Db\ResultEmpty;
+        $this->assertEquals(0, $r->changes());
+        $this->assertEquals(0, $r->lastId());
+    }
+
+    public function testIterateOverResults() {
+        $rows = [];
+        foreach (new Db\ResultEmpty as $index => $row) {
+            $rows[$index] = $row['col'];
+        }
+        $this->assertEquals([], $rows);
+    }
+
+    public function testGetSingleValues() {
+        $test = new Db\ResultEmpty;
+        $this->assertSame(null, $test->getValue());
+    }
+
+    public function testGetRows() {
+        $test = new Db\ResultEmpty;
+        $this->assertSame(null, $test->getRow());
+    }
+
+    public function testGetAllRows() {
+        $test = new Db\ResultEmpty;
+        $rows = [];
+        $this->assertEquals($rows, $test->getAll());
+    }
+}

tests/phpunit.xml

@@ -56,6 +56,7 @@
     <testsuite name="Database drivers">
         <file>Db/TestTransaction.php</file>
         <file>Db/TestResultAggregate.php</file>
+        <file>Db/TestResultEmpty.php</file>
         <file>Db/SQLite3/TestDbResultSQLite3.php</file>
         <file>Db/SQLite3/TestDbStatementSQLite3.php</file>
         <file>Db/SQLite3/TestDbDriverCreationSQLite3.php</file>