Add SystemProperties

core/shared/src/main/scala/cats/effect/IO.scala

@@ -40,7 +40,7 @@ import cats.data.Ior
 import cats.effect.instances.spawn
 import cats.effect.kernel.CancelScope
 import cats.effect.kernel.GenTemporal.handleDuration
-import cats.effect.std.{Backpressure, Console, Env, Supervisor, UUIDGen}
+import cats.effect.std.{Backpressure, Console, Env, Supervisor, SystemProperties, UUIDGen}
 import cats.effect.tracing.{Tracing, TracingEvent}
 import cats.effect.unsafe.IORuntime
 import cats.syntax._
@@ -2159,6 +2159,8 @@ object IO extends IOCompanionPlatform with IOLowPriorityImplicits with TuplePara
 
   implicit val envForIO: Env[IO] = Env.make
 
+  implicit val systemPropertiesForIO: SystemProperties[IO] = SystemProperties.make
+
   // This is cached as a val to save allocations, but it uses ops from the Async
   // instance which is also cached as a val, and therefore needs to appear
   // later in the file

std/shared/src/main/scala/cats/effect/std/SystemProperties.scala

@@ -0,0 +1,132 @@
+/*
+ * Copyright 2020-2024 Typelevel
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package cats.effect.std
+
+import cats.{~>, Applicative, Functor}
+import cats.data.{EitherT, IorT, Kleisli, OptionT, ReaderWriterStateT, StateT, WriterT}
+import cats.effect.kernel.Sync
+import cats.kernel.Monoid
+
+trait SystemProperties[F[_]] { self =>
+
+  /**
+   * Gets the system property indicated by `key`.
+   */
+  def get(key: String): F[Option[String]]
+
+  /**
+   * Sets the system property indicated by `key`.
+   */
+  def set(key: String, value: String): F[Option[String]]
+
+  /**
+   * Removes the system property indicated by `key`.
+   */
+  def clear(key: String): F[Option[String]]
+
+  def mapK[G[_]](f: F ~> G): SystemProperties[G] = new SystemProperties[G] {
+    def get(key: String) = f(self.get(key))
+    def set(key: String, value: String) = f(self.set(key, value))
+    def clear(key: String) = f(self.clear(key))
+  }
+}
+
+object SystemProperties {
+
+  /**
+   * Summoner method for `SystemProperties` instances.
+   */
+  def apply[F[_]](implicit ev: SystemProperties[F]): ev.type = ev
+
+  /**
+   * Constructs a `SystemProperties` instance for `F` data types that are
+   * [[cats.effect.kernel.Sync]].
+   */
+  def make[F[_]](implicit F: Sync[F]): SystemProperties[F] = new SyncSystemProperties[F]
+
+  /**
+   * [[SystemProperties]] instance built for `cats.data.EitherT` values initialized with any `F`
+   * data type that also implements [[SystemProperties]].
+   */
+  implicit def catsEitherTSystemProperties[F[_]: SystemProperties: Functor, L]
+      : SystemProperties[EitherT[F, L, *]] =
+    SystemProperties[F].mapK(EitherT.liftK)
+
+  /**
+   * [[SystemProperties]] instance built for `cats.data.Kleisli` values initialized with any `F`
+   * data type that also implements [[SystemProperties]].
+   */
+  implicit def catsKleisliSystemProperties[F[_]: SystemProperties, R]
+      : SystemProperties[Kleisli[F, R, *]] =
+    SystemProperties[F].mapK(Kleisli.liftK)
+
+  /**
+   * [[SystemProperties]] instance built for `cats.data.OptionT` values initialized with any `F`
+   * data type that also implements [[SystemProperties]].
+   */
+  implicit def catsOptionTSystemProperties[F[_]: SystemProperties: Functor]
+      : SystemProperties[OptionT[F, *]] =
+    SystemProperties[F].mapK(OptionT.liftK)
+
+  /**
+   * [[SystemProperties]] instance built for `cats.data.StateT` values initialized with any `F`
+   * data type that also implements [[SystemProperties]].
+   */
+  implicit def catsStateTSystemProperties[F[_]: SystemProperties: Applicative, S]
+      : SystemProperties[StateT[F, S, *]] =
+    SystemProperties[F].mapK(StateT.liftK)
+
+  /**
+   * [[SystemProperties]] instance built for `cats.data.WriterT` values initialized with any `F`
+   * data type that also implements [[SystemProperties]].
+   */
+  implicit def catsWriterTSystemProperties[
+      F[_]: SystemProperties: Applicative,
+      L: Monoid
+  ]: SystemProperties[WriterT[F, L, *]] =
+    SystemProperties[F].mapK(WriterT.liftK)
+
+  /**
+   * [[SystemProperties]] instance built for `cats.data.IorT` values initialized with any `F`
+   * data type that also implements [[SystemProperties]].
+   */
+  implicit def catsIorTSystemProperties[F[_]: SystemProperties: Functor, L]
+      : SystemProperties[IorT[F, L, *]] =
+    SystemProperties[F].mapK(IorT.liftK)
+
+  /**
+   * [[SystemProperties]] instance built for `cats.data.ReaderWriterStateT` values initialized
+   * with any `F` data type that also implements [[SystemProperties]].
+   */
+  implicit def catsReaderWriterStateTSystemProperties[
+      F[_]: SystemProperties: Applicative,
+      E,
+      L: Monoid,
+      S
+  ]: SystemProperties[ReaderWriterStateT[F, E, L, S, *]] =
+    SystemProperties[F].mapK(ReaderWriterStateT.liftK)
+
+  private[std] final class SyncSystemProperties[F[_]](implicit F: Sync[F])
+      extends SystemProperties[F] {
+
+    def get(key: String) = F.delay(Option(System.getProperty(key)))
+
+    def set(key: String, value: String) = F.blocking(Option(System.setProperty(key, value)))
+
+    def clear(key: String) = F.blocking(Option(System.clearProperty(key)))
+  }
+}

tests/shared/src/test/scala/cats/effect/std/SystemPropertiesSpec.scala

@@ -0,0 +1,39 @@
+/*
+ * Copyright 2020-2024 Typelevel
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package cats.effect
+package std
+
+class SystemPropertiesSpec extends BaseSpec {
+
+  "SystemProperties" should {
+    "retrieve a property just set" in real {
+      Random.javaUtilConcurrentThreadLocalRandom[IO].nextString(12).flatMap { key =>
+        SystemProperties[IO].set(key, "bar") *>
+          SystemProperties[IO].get(key).flatMap(x => IO(x mustEqual Some("bar")))
+      }
+    }
+    "return none for a non-existent property" in real {
+      SystemProperties[IO].get("MADE_THIS_UP").flatMap(x => IO(x must beNone))
+    }
+    "clear" in real {
+      Random.javaUtilConcurrentThreadLocalRandom[IO].nextString(12).flatMap { key =>
+        SystemProperties[IO].set(key, "bar") *> SystemProperties[IO].clear(key) *>
+          SystemProperties[IO].get(key).flatMap(x => IO(x must beNone))
+      }
+    }
+  }
+}