char(n) / bpchar fix (#72)

Author: tanner0101

Sources/PostgresNIO/Data/PostgresData+Int.swift

@@ -115,8 +115,10 @@ private extension PostgresData {
         switch self.formatCode {
         case .binary:
             switch self.type {
-            case .char:
-                assert(value.readableBytes == 1)
+            case .char, .bpchar:
+                guard value.readableBytes == 1 else {
+                    return nil
+                }
                 guard let uint8 = value.getInteger(at: value.readerIndex, as: UInt8.self) else {
                     return nil
                 }

Sources/PostgresNIO/Data/PostgresData+String.swift

@@ -47,7 +47,7 @@ extension PostgresData {
             case .int2, .int4, .int8:
                 return self.int?.description
             case .bpchar:
-                return self.character?.description
+                return value.readString(length: value.readableBytes)
             default:
                 if self.type.isUserDefined {
                     // custom type

Tests/PostgresNIOTests/PostgresNIOTests.swift

@@ -1077,6 +1077,23 @@ final class PostgresNIOTests: XCTestCase {
         }
     }
 
+    // https://github.com/vapor/postgres-nio/issues/71
+    func testChar1Serialization() throws {
+        let conn = try PostgresConnection.test(on: eventLoop).wait()
+        defer { try! conn.close().wait() }
+        let rows = try conn.query("""
+        select
+            '5'::char(1) as one,
+            '5'::char(2) as two
+        """).wait()
+        XCTAssertEqual(rows[0].column("one")?.uint8, 53)
+        XCTAssertEqual(rows[0].column("one")?.uint16, 53)
+        XCTAssertEqual(rows[0].column("one")?.string, "5")
+        XCTAssertEqual(rows[0].column("two")?.uint8, nil)
+        XCTAssertEqual(rows[0].column("two")?.uint16, nil)
+        XCTAssertEqual(rows[0].column("two")?.string, "5 ")
+    }
+
     func testUserDefinedType() throws {
         let conn = try PostgresConnection.test(on: eventLoop).wait()
         defer { try! conn.close().wait() }