Adds support for returning extended error codes

Sources/SQLite/Core/Connection.swift

@@ -156,6 +156,13 @@ public final class Connection {
         Int(sqlite3_total_changes(handle))
     }
 
+    /// Whether or not the database will return extended error codes when errors are handled.
+    public var usesExtendedErrorCodes: Bool = false {
+        didSet {
+            sqlite3_extended_result_codes(handle, usesExtendedErrorCodes ? 1 : 0)
+        }
+    }
+
     // MARK: - Execute
 
     /// Executes a batch of SQL statements.

Sources/SQLite/Core/Result.swift

@@ -21,11 +21,27 @@ public enum Result: Error {
     /// - statement: the statement which produced the error
     case error(message: String, code: Int32, statement: Statement?)
 
+    /// Represents a SQLite specific [extended error code] (https://sqlite.org/rescode.html#primary_result_codes_versus_extended_result_codes)
+    ///
+    /// - message: English-language text that describes the error
+    ///
+    /// - extendedCode: SQLite [extended error code](https://sqlite.org/rescode.html#extended_result_code_list)
+    ///
+    /// - statement: the statement which produced the error
+    case extendedError(message: String, extendedCode: Int32, statement: Statement?)
+
     init?(errorCode: Int32, connection: Connection, statement: Statement? = nil) {
         guard !Result.successCodes.contains(errorCode) else { return nil }
 
         let message = String(cString: sqlite3_errmsg(connection.handle))
-        self = .error(message: message, code: errorCode, statement: statement)
+
+        guard connection.usesExtendedErrorCodes else {
+            self = .error(message: message, code: errorCode, statement: statement)
+            return
+        }
+
+        let extendedErrorCode = sqlite3_extended_errcode(connection.handle)
+        self = .extendedError(message: message, extendedCode: extendedErrorCode, statement: statement)
     }
 
 }
@@ -40,6 +56,12 @@ extension Result: CustomStringConvertible {
             } else {
                 return "\(message) (code: \(errorCode))"
             }
+        case let .extendedError(message, extendedCode, statement):
+            if let statement = statement {
+                return "\(message) (\(statement)) (extended code: \(extendedCode))"
+            } else {
+                return "\(message) (extended code: \(extendedCode))"
+            }
         }
     }
 }

Tests/SQLiteTests/Core/ConnectionTests.swift

@@ -111,6 +111,10 @@ class ConnectionTests: SQLiteTestCase {
         XCTAssertEqual(2, db.totalChanges)
     }
 
+    func test_useExtendedErrorCodes_returnsFalseDefault() throws {
+        XCTAssertFalse(db.usesExtendedErrorCodes)
+    }
+
     func test_prepare_preparesAndReturnsStatements() throws {
         _ = try db.prepare("SELECT * FROM users WHERE admin = 0")
         _ = try db.prepare("SELECT * FROM users WHERE admin = ?", 0)

Tests/SQLiteTests/Core/ResultTests.swift

@@ -53,4 +53,17 @@ class ResultTests: XCTestCase {
         XCTAssertEqual("not an error (SELECT 1) (code: 21)",
             Result(errorCode: SQLITE_MISUSE, connection: connection, statement: statement)?.description)
     }
+
+    func test_init_extended_with_other_code_returns_error() {
+        connection.usesExtendedErrorCodes = true
+        if case .some(.extendedError(let message, let extendedCode, let statement)) =
+            Result(errorCode: SQLITE_MISUSE, connection: connection, statement: nil) {
+            XCTAssertEqual("not an error", message)
+            XCTAssertEqual(extendedCode, 0)
+            XCTAssertNil(statement)
+            XCTAssert(connection === connection)
+        } else {
+            XCTFail("no error")
+        }
+    }
 }

Tests/SQLiteTests/Typed/QueryIntegrationTests.swift

@@ -229,6 +229,19 @@ class QueryIntegrationTests: SQLiteTestCase {
         }
     }
 
+    func test_extendedErrorCodes_catchConstraintError() throws {
+        db.usesExtendedErrorCodes = true
+        try db.run(users.insert(email <- "[email protected]"))
+        do {
+            try db.run(users.insert(email <- "[email protected]"))
+            XCTFail("expected error")
+        } catch let Result.extendedError(_, extendedCode, _) where extendedCode == 2_067 {
+            // SQLITE_CONSTRAINT_UNIQUE expected
+        } catch let error {
+            XCTFail("unexpected error: \(error)")
+        }
+    }
+
     // https://github.com/stephencelis/SQLite.swift/issues/285
     func test_order_by_random() throws {
         try insertUsers(["a", "b", "c'"])