fix: return false from fetchField on empty result

flight/database/PdoWrapper.php

@@ -91,11 +91,14 @@ public function runQuery(string $sql, array $params = []): PDOStatement
      * @param string $sql   - Ex: "SELECT id FROM table WHERE something = ?"
      * @param array<int|string,mixed> $params - Ex: [ $something ]
      *
-     * @return mixed
+     * @return mixed|false
      */
     public function fetchField(string $sql, array $params = [])
     {
         $result = $this->fetchRow($sql, $params);
+        if ($result === null || count($result) === 0) {
+            return false;
+        }
         $data = $result->getData();
         return reset($data);
     }

tests/PdoWrapperTest.php

@@ -68,9 +68,37 @@ public function testRunQueryDeleteStatement(): void
     public function testFetchField(): void
     {
         $id = $this->pdo_wrapper->fetchField('SELECT id FROM test WHERE name = ?', ['two']);
+        // PDO SQLite may return numeric strings on PHP < 8.1
         $this->assertEquals(2, $id);
     }
 
+    public function testFetchFieldReturnsFalseWhenNoResults(): void
+    {
+        $id = $this->pdo_wrapper->fetchField('SELECT id FROM test WHERE id = ?', [999]);
+        $this->assertSame(false, $id);
+    }
+
+    public function testFetchFieldReturnsNullWhenColumnIsSqlNull(): void
+    {
+        $this->pdo_wrapper->exec('INSERT INTO test (name) VALUES (NULL)');
+        $value = $this->pdo_wrapper->fetchField('SELECT name FROM test WHERE name IS NULL');
+        $this->assertNull($value);
+    }
+
+    public function testFetchFieldReturnsZero(): void
+    {
+        $value = $this->pdo_wrapper->fetchField('SELECT 0');
+        // PDO SQLite may return '0' on PHP < 8.1
+        $this->assertEquals(0, $value);
+    }
+
+    public function testFetchFieldReturnsEmptyString(): void
+    {
+        $this->pdo_wrapper->exec('INSERT INTO test (name) VALUES ("")');
+        $value = $this->pdo_wrapper->fetchField('SELECT name FROM test WHERE name = ?', ['']);
+        $this->assertSame('', $value);
+    }
+
     public function testFetchRow(): void
     {
         $row = $this->pdo_wrapper->fetchRow('SELECT * FROM test WHERE name = ?', ['two']);

tests/SimplePdoTest.php

@@ -460,12 +460,40 @@ public function testTransactionRethrowsException(): void
     public function testFetchFieldReturnsValue(): void
     {
         $name = $this->db->fetchField('SELECT name FROM users WHERE id = ?', [1]);
-        $this->assertEquals('John', $name);
+        $this->assertSame('John', $name);
     }
 
     public function testFetchFieldReturnsFirstColumn(): void
     {
         $id = $this->db->fetchField('SELECT id, name FROM users WHERE id = ?', [1]);
+        // PDO SQLite may return numeric strings on PHP < 8.1
         $this->assertEquals(1, $id);
     }
+
+    public function testFetchFieldReturnsFalseWhenNoResults(): void
+    {
+        $value = $this->db->fetchField('SELECT name FROM users WHERE id = ?', [999]);
+        $this->assertSame(false, $value);
+    }
+
+    public function testFetchFieldReturnsNullWhenColumnIsSqlNull(): void
+    {
+        $this->db->exec('INSERT INTO users (name, email) VALUES (NULL, "null@example.com")');
+        $value = $this->db->fetchField('SELECT name FROM users WHERE email = ?', ['null@example.com']);
+        $this->assertNull($value);
+    }
+
+    public function testFetchFieldReturnsZero(): void
+    {
+        $value = $this->db->fetchField('SELECT 0');
+        // PDO SQLite may return '0' on PHP < 8.1
+        $this->assertEquals(0, $value);
+    }
+
+    public function testFetchFieldReturnsEmptyString(): void
+    {
+        $this->db->exec('INSERT INTO users (name, email) VALUES ("", "empty@example.com")');
+        $value = $this->db->fetchField('SELECT name FROM users WHERE email = ?', ['empty@example.com']);
+        $this->assertSame('', $value);
+    }
 }