add maybeFound convenience extension method (#376)

dynamodb/src/it/scala/zio/dynamodb/TypeSafeApiCrudSpec.scala

@@ -5,7 +5,8 @@ import zio.test._
 import zio.test.assertTrue
 import zio.test.Assertion._
 import zio.dynamodb.DynamoDBError.ItemError
-import zio.dynamodb.DynamoDBQuery.{ deleteFrom, forEach, get, put, scanAll, update }
+import zio.dynamodb.DynamoDBQuery.{ deleteFrom, forEach, get, put, putItem, scanAll, update }
+import zio.dynamodb.syntax._
 import zio.Chunk
 import software.amazon.awssdk.services.dynamodb.model.ConditionalCheckFailedException
 import zio.stream.ZStream
@@ -51,6 +52,27 @@ object TypeSafeApiCrudSpec extends DynamoDBLocalSpec {
           } yield assertTrue(p == person)
         }
       },
+      test("and get using maybeFound extension method") {
+        withSingleIdKeyTable { tableName =>
+          val person = Person("1", "Smith", Some("John"), 21)
+          for {
+            _               <- put(tableName, person).execute
+            personFound     <- get(tableName)(Person.id.partitionKey === "1").execute.maybeFound
+            personNotFound  <- get(tableName)(Person.id.partitionKey === "DOES_NOT_EXIST").execute.maybeFound
+            _               <- putItem(tableName, Item("id" -> "WILL_GIVE_DECODE_ERROR")).execute
+            decodeErrorExit <-
+              get(tableName)(Person.id.partitionKey === "WILL_GIVE_DECODE_ERROR").execute.maybeFound.exit
+          } yield assertTrue(personFound == Some(person) && personNotFound == None) && assert(decodeErrorExit)(
+            fails(
+              equalTo(
+                DynamoDBError.ItemError.DecodingError(
+                  "field 'surname' not found in Map(Map(String(id) -> String(WILL_GIVE_DECODE_ERROR)))"
+                )
+              )
+            )
+          )
+        }
+      },
       test("with condition expression that id not exists fails when item exists") {
         withSingleIdKeyTable { tableName =>
           val person = Person("1", "Smith", Some("John"), 21)

dynamodb/src/main/scala/zio/dynamodb/syntax.scala

@@ -0,0 +1,20 @@
+package zio.dynamodb
+
+import zio.ZIO
+
+object syntax {
+  implicit class MaybeFound[R, A](zio: ZIO[R, DynamoDBError, Either[DynamoDBError.ItemError, A]]) {
+
+    /**
+     * Moves Left[ItemError.DecodingError] to the error channel and returns Some(a) if the item is found else None
+     * eg {{{ DynamoDBQuery.get("table")(Person.id.partitionKey === 1).execute.maybeFound }}}
+     */
+    def maybeFound: ZIO[R, DynamoDBError, Option[A]] =
+      zio.flatMap {
+        case Left(e @ DynamoDBError.ItemError.DecodingError(_)) => ZIO.fail(e)
+        case Left(DynamoDBError.ItemError.ValueNotFound(_))     => ZIO.succeed(None)
+        case Right(a)                                           => ZIO.succeed(Some(a))
+      }
+  }
+
+}

examples/src/main/scala/zio/dynamodb/examples/dynamodblocal/DynamoDBLocalMain.scala

@@ -13,6 +13,7 @@ import zio.dynamodb.DynamoDBExecutor
 import zio.dynamodb.DynamoDBQuery.get
 import zio.dynamodb.DynamoDBQuery.put
 import zio.dynamodb.ProjectionExpression
+import zio.dynamodb.syntax._
 import zio.schema.DeriveSchema
 import zio.schema.Schema
 
@@ -66,9 +67,9 @@ object DynamoDBLocalMain extends ZIOAppDefault {
   val examplePerson = Person(1, "avi")
 
   private val program = for {
-    _      <- put("person", examplePerson).execute
-    person <- get("person")(Person.id.partitionKey === 1).execute
-    _      <- zio.Console.printLine(s"hello $person")
+    _           <- put("person", examplePerson).execute
+    maybePerson <- get("person")(Person.id.partitionKey === 1).execute.maybeFound
+    _           <- zio.Console.printLine(s"hello $maybePerson")
   } yield ()
 
   override def run =