add isUserDefined + fix optional (vapor#75)

Author: tanner0101

Sources/PostgresNIO/Data/PostgresData+Optional.swift

@@ -12,7 +12,7 @@ extension Optional: PostgresDataConvertible where Wrapped: PostgresDataConvertib
         case .some(let wrapped):
             return wrapped.postgresData
         case .none:
-            return PostgresData.null
+            return .init(type: Wrapped.postgresDataType, value: nil)
         }
     }
 }

Sources/PostgresNIO/Data/PostgresData+String.swift

@@ -49,7 +49,12 @@ extension PostgresData {
             case .bpchar:
                 return self.character?.description
             default:
-                return nil
+                if self.type.isUserDefined {
+                    // custom type
+                    return value.readString(length: value.readableBytes)
+                } else {
+                    return nil
+                }
             }
         case .text:
             guard let string = value.readString(length: value.readableBytes) else {

Sources/PostgresNIO/Data/PostgresData.swift

@@ -71,7 +71,12 @@ public struct PostgresData: CustomStringConvertible, CustomDebugStringConvertibl
         case .jsonbArray:
             description = self.array?.description
         default:
-            description = nil
+            if self.type.isUserDefined {
+                // custom type
+                description = value.readString(length: value.readableBytes)
+            } else {
+                description = nil
+            }
         }
 
         if let description = description {

Sources/PostgresNIO/Data/PostgresDataType.swift

@@ -106,6 +106,13 @@ public struct PostgresDataType: Codable, Equatable, ExpressibleByIntegerLiteral,
 
     /// The raw data type code recognized by PostgreSQL.
     public var rawValue: UInt32
+
+    /// Returns `true` if the type's raw value is greater than `2^14`.
+    /// This _appears_ to be true for all user-defined types, but I don't
+    /// have any documentation to back this up.
+    public var isUserDefined: Bool {
+        self.rawValue >= 1 << 14
+    }
 
     /// See `ExpressibleByIntegerLiteral.init(integerLiteral:)`
     public init(integerLiteral value: UInt32) {

Tests/PostgresNIOTests/PostgresNIOTests.swift

@@ -1028,6 +1028,27 @@ final class PostgresNIOTests: XCTestCase {
             XCTFail("\(error)")
         }
     }
+
+    func testUserDefinedType() throws {
+        let conn = try PostgresConnection.test(on: eventLoop).wait()
+        defer { try! conn.close().wait() }
+
+        _ = try conn.query("DROP TYPE IF EXISTS foo").wait()
+        _ = try conn.query("CREATE TYPE foo AS ENUM ('bar', 'qux')").wait()
+        defer {
+            _ = try! conn.query("DROP TYPE foo").wait()
+        }
+        let res = try conn.query("SELECT 'qux'::foo as foo").wait()
+        XCTAssertEqual(res[0].column("foo")?.string, "qux")
+    }
+
+    func testNullBind() throws {
+        let conn = try PostgresConnection.test(on: eventLoop).wait()
+        defer { try! conn.close().wait() }
+
+        let res = try conn.query("SELECT $1::text as foo", [String?.none.postgresData!]).wait()
+        XCTAssertEqual(res[0].column("foo")?.string, nil)
+    }
 }
 
 private func performance(function: String = #function) -> Bool {