Update README to show new CompletedRequestMap constructors (#472)

* Update doco with new CompletedRequestMap constructors

* Update doco and improve `fromIterableWith`

docs/creating-data-sources.md

@@ -41,22 +41,20 @@ val identifier: String = "UserDataSource"
 We will define two different behaviors depending on whether we receive a single request or multiple requests at once. For each request, we need to insert into the result map a value of type `Exit` (`fail` for an error and `succeed` for a success).
 
 ```scala mdoc:silent
-def run(requests: Chunk[GetUserName]): ZIO[Any, Nothing, CompletedRequestMap] = {
-  val resultMap = CompletedRequestMap.empty
+def run(requests: Chunk[GetUserName]): ZIO[Any, Nothing, CompletedRequestMap] =
   requests.toList match {
     case request :: Nil =>
       // get user by ID e.g. SELECT name FROM users WHERE id = $id
       val result: Task[String] = ???
-      result.exit.map(resultMap.insert(request, _))
+      result.exit.map(CompletedRequestMap.single(request, _))
     case batch =>
       // get multiple users at once e.g. SELECT id, name FROM users WHERE id IN ($ids)
       val result: Task[List[(Int, String)]] = ???
-      result.fold(
-        err => requests.foldLeft(resultMap) { case (map, req) => map.insert(req, Exit.fail(err)) },
-        _.foldLeft(resultMap) { case (map, (id, name)) => map.insert(GetUserName(id), Exit.succeed(name)) }
+      result.foldCause(
+        CompletedRequestMap.failCause(requests, _),
+        CompletedRequestMap.fromIterableWith(_)(kv => GetUserName(kv._1), kv => Exit.succeed(kv._2))
       )
   }
-}
 ```
 
 Now to build a `ZQuery`, we can use `ZQuery.fromRequest` and just pass the request and the data source:

docs/index.md

@@ -89,35 +89,27 @@ object ZQueryExample extends ZIOAppDefault {
     new DataSource.Batched[Any, GetUserName] {
       val identifier: String = "UserDataSource"
 
-      def run(requests: Chunk[GetUserName])(implicit trace: Trace): ZIO[Any, Nothing, CompletedRequestMap] = {
-        val resultMap = CompletedRequestMap.empty
+      def run(requests: Chunk[GetUserName])(implicit trace: Trace): ZIO[Any, Nothing, CompletedRequestMap] =
         requests.toList match {
           case request :: Nil =>
             val result: Task[String] = {
               // get user by ID e.g. SELECT name FROM users WHERE id = $id
               ZIO.succeed(???)
             }
 
-            result.exit.map(resultMap.insert(request, _))
+            result.exit.map(CompletedRequestMap.single(request, _))
 
           case batch: Seq[GetUserName] =>
             val result: Task[List[(Int, String)]] = {
               // get multiple users at once e.g. SELECT id, name FROM users WHERE id IN ($ids)
               ZIO.succeed(???)
             }
 
-            result.fold(
-              err =>
-                requests.foldLeft(resultMap) { case (map, req) =>
-                  map.insert(req, Exit.fail(err))
-                },
-              _.foldLeft(resultMap) { case (map, (id, name)) =>
-                map.insert(GetUserName(id), Exit.succeed(name))
-              }
+            result.foldCause(
+              CompletedRequestMap.failCause(requests, _),
+              CompletedRequestMap.fromIterableWith(_)(kv => GetUserName(kv._1), kv => Exit.succeed(kv._2))
             )
         }
-      }
-
     }
 
   def getUserNameById(id: Int): ZQuery[Any, Throwable, String] =

zio-query/shared/src/main/scala/zio/query/CompletedRequestMap.scala

@@ -170,18 +170,6 @@ object CompletedRequestMap {
   def fromIterable[E, A](iterable: Iterable[(Request[E, A], Exit[E, A])]): CompletedRequestMap =
     Mutable(mutable.HashMap.from(iterable))
 
-  /**
-   * Constructs a completed requests map an iterable of requests and a function
-   * that maps each request to a result
-   */
-  def fromIterableWith[E, A, B](
-    iterable: Iterable[A]
-  )(f: A => Exit[E, B])(implicit ev: A <:< Request[E, B]): CompletedRequestMap = {
-    val map = Mutable.empty(iterable.size)
-    iterable.foreach(req => map.update(req, f(req)))
-    map
-  }
-
   /**
    * Constructs a completed requests map from the specified optional results.
    */
@@ -195,6 +183,26 @@ object CompletedRequestMap {
     map
   }
 
+  /**
+   * Constructs a completed requests map an iterable of A and functions that map
+   * each A to a request and a result
+   *
+   * @param f1
+   *   function that maps each element of A to a request
+   * @param f2
+   *   function that maps each element of A to an Exit, e.g., Exit.succeed(_)
+   */
+  def fromIterableWith[E, A, B](
+    iterable: Iterable[A]
+  )(
+    f1: A => Request[E, B],
+    f2: A => Exit[E, B]
+  ): CompletedRequestMap = {
+    val map = Mutable.empty(iterable.size)
+    iterable.foreach(req => map.update(f1(req), f2(req)))
+    map
+  }
+
   /**
    * Constructs a completed requests map containing a single entry
    */

zio-query/shared/src/main/scala/zio/query/DataSource.scala

@@ -226,7 +226,7 @@ object DataSource {
     new DataSource.Batched[Any, A] {
       val identifier: String = name
       def run(requests: Chunk[A])(implicit trace: Trace): ZIO[Any, Nothing, CompletedRequestMap] =
-        ZIO.succeed(CompletedRequestMap.fromIterableWith(requests)(a => Exit.succeed(f(a))))
+        ZIO.succeed(CompletedRequestMap.fromIterableWith(requests)(ev.apply, a => Exit.succeed(f(a))))
     }
 
   /**