From a3277888ca50c1fb241c54ba17e983dda6002caa Mon Sep 17 00:00:00 2001
From: Yisrael Union <yunion@caesars.com>
Date: Tue, 17 Sep 2024 03:09:30 -0400
Subject: [PATCH] add apply method for Mapref

---
 package-lock.json                             | 36 +------------------
 .../main/scala/cats/effect/std/MapRef.scala   | 16 +++++++++
 .../scala/cats/effect/std/MapRefSpec.scala    | 17 ++++++---
 3 files changed, 30 insertions(+), 39 deletions(-)

diff --git a/package-lock.json b/package-lock.json
index 7c5355ceb9..69951c8a6a 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,39 +1,5 @@
 {
-  "name": "cats-effect",
-  "lockfileVersion": 2,
-  "requires": true,
-  "packages": {
-    "": {
-      "devDependencies": {
-        "source-map-support": "^0.5.19"
-      }
-    },
-    "node_modules/buffer-from": {
-      "version": "1.1.2",
-      "resolved": "https://registry.npmjs.org/buffer-from/-/buffer-from-1.1.2.tgz",
-      "integrity": "sha512-E+XQCRwSbaaiChtv6k6Dwgc+bx+Bs6vuKJHHl5kox/BaKbhiXzqQOwK4cO22yElGp2OCmjwVhT3HmxgyPGnJfQ==",
-      "dev": true
-    },
-    "node_modules/source-map": {
-      "version": "0.6.1",
-      "resolved": "https://registry.npmjs.org/source-map/-/source-map-0.6.1.tgz",
-      "integrity": "sha512-UjgapumWlbMhkBgzT7Ykc5YXUT46F0iKu8SGXq0bcwP5dz/h0Plj6enJqjz1Zbq2l5WaqYnrVbwWOWMyF3F47g==",
-      "dev": true,
-      "engines": {
-        "node": ">=0.10.0"
-      }
-    },
-    "node_modules/source-map-support": {
-      "version": "0.5.19",
-      "resolved": "https://registry.npmjs.org/source-map-support/-/source-map-support-0.5.19.tgz",
-      "integrity": "sha512-Wonm7zOCIJzBGQdB+thsPar0kYuCIzYvxZwlBa87yi/Mdjv7Tip2cyVbLj5o0cFPN4EVkuTwb3GDDyUx2DGnGw==",
-      "dev": true,
-      "dependencies": {
-        "buffer-from": "^1.0.0",
-        "source-map": "^0.6.0"
-      }
-    }
-  },
+  "lockfileVersion": 1,
   "dependencies": {
     "buffer-from": {
       "version": "1.1.2",
diff --git a/std/shared/src/main/scala/cats/effect/std/MapRef.scala b/std/shared/src/main/scala/cats/effect/std/MapRef.scala
index 17b8d4ac97..69b6dd80d2 100644
--- a/std/shared/src/main/scala/cats/effect/std/MapRef.scala
+++ b/std/shared/src/main/scala/cats/effect/std/MapRef.scala
@@ -45,6 +45,22 @@ trait MapRef[F[_], K, V] extends Function1[K, Ref[F, V]] {
 
 object MapRef extends MapRefCompanionPlatform {
 
+  /**
+   * the default Constructor for MapRef.
+   * If Async is available, it will use a ConcurrentHashMap, otherwise it will use a sharded immutable map.
+   */
+  def apply[F[_]: Concurrent, K, V](): F[MapRef[F, K, Option[V]]] = {
+
+    Concurrent[F] match {
+      case a: Async[_] =>
+        implicit val async: Async[F] = a
+        ofConcurrentHashMap()
+      case _ =>
+        ofShardedImmutableMap[F, K, V](Runtime.getRuntime.availableProcessors())
+    }
+
+  }
+
   /**
    * Creates a sharded map ref to reduce atomic contention on the Map, given an efficient and
    * equally distributed hash, the contention should allow for interaction like a general
diff --git a/tests/shared/src/test/scala/cats/effect/std/MapRefSpec.scala b/tests/shared/src/test/scala/cats/effect/std/MapRefSpec.scala
index 2ee9166631..9a8cdf4886 100644
--- a/tests/shared/src/test/scala/cats/effect/std/MapRefSpec.scala
+++ b/tests/shared/src/test/scala/cats/effect/std/MapRefSpec.scala
@@ -16,18 +16,27 @@
 
 package cats.effect.std
 
-import cats._
+import cats.*
 import cats.data.State
-import cats.effect._
-import cats.implicits._
+import cats.effect.*
+import cats.effect.unsafe.implicits.global
+import cats.implicits.*
 
-import scala.concurrent.duration._
+import java.util.concurrent.ConcurrentHashMap
+import scala.concurrent.duration.*
 
 class MapRefSpec extends BaseSpec {
   private val smallDelay: IO[Unit] = IO.sleep(20.millis)
   private def awaitEqual[A: Eq](t: IO[A], success: A): IO[Unit] =
     t.flatMap(a => if (Eq[A].eqv(a, success)) IO.unit else smallDelay *> awaitEqual(t, success))
 
+  "MapRef[Async]()" should {
+    "be instance of ConcurrentHashMap" in real {
+        val mapRef =  MapRef[IO,Int, Int]().unsafeRunSync()
+      mapRef.isInstanceOf[ConcurrentHashMap[ Int, Int]] must_=== true
+
+    }
+  }
   "MapRef.ofSingleImmutableMapRef" should {
 
     "concurrent modifications" in real {