Don't drop offset when fetching first row

Fixes stephencelis#110.

Signed-off-by: Stephen Celis <stephen@stephencelis.com>

Author: stephencelis

SQLite Tests/QueryTests.swift

@@ -285,6 +285,13 @@ class QueryTests: SQLiteTestCase {
         AssertSQL("SELECT * FROM \"users\" LIMIT 1")
     }
 
+    func test_first_withOffset_retainsOffset() {
+        insertUsers("alice", "betsy")
+
+        XCTAssertEqual(2, users.limit(2, offset: 1).first![id])
+        AssertSQL("SELECT * FROM \"users\" LIMIT 1 OFFSET 1")
+    }
+
     func test_isEmpty_returnsWhetherOrNotTheQueryIsEmpty() {
         XCTAssertTrue(users.isEmpty)
 

SQLite/Query.swift

@@ -731,7 +731,7 @@ public struct Query {
 
     /// The first row (or nil if the query returns no rows).
     public var first: Row? {
-        var generator = limit(1).generate()
+        var generator = limit(to: 1, offset: limit?.offset).generate()
         return generator.next()
     }