Introduce //libs-scala/scala-utils (#6935)

* Moving `Statements.discard` from //ledger-server/http-json into //libs-scala/scala-utils

changelog_begin
changelog_end

* Add new module to the published artifacts

* `com.daml.scalautil` instead of `com.daml.scala.util`

@S11001001: That's because if this is in classpath and you import com.daml._,
you have a different scala in scope than the one you expect.

ledger-service/http-json/BUILD.bazel

@@ -41,6 +41,7 @@ da_scala_library(
         "//ledger/ledger-api-common",
         "//libs-scala/auth-utils",
         "//libs-scala/ports",
+        "//libs-scala/scala-utils",
         "@maven//:com_chuusai_shapeless_2_12",
         "@maven//:com_github_scopt_scopt_2_12",
         "@maven//:com_lihaoyi_sourcecode_2_12",
@@ -84,6 +85,7 @@ da_scala_binary(
         "//ledger/ledger-api-common",
         "//libs-scala/auth-utils",
         "//libs-scala/ports",
+        "//libs-scala/scala-utils",
         "@maven//:ch_qos_logback_logback_classic",
         "@maven//:com_chuusai_shapeless_2_12",
         "@maven//:com_github_scopt_scopt_2_12",
@@ -129,6 +131,7 @@ da_scala_test(
         "//ledger-service/db-backend",
         "//ledger-service/lf-value-json",
         "//ledger/ledger-api-common",
+        "//libs-scala/scala-utils",
         "//libs-scala/scalatest-utils",
         "@maven//:com_chuusai_shapeless_2_12",
         "@maven//:com_lihaoyi_sourcecode_2_12",
@@ -184,6 +187,7 @@ da_scala_test(
         "//libs-scala/auth-utils",
         "//libs-scala/ports",
         "//libs-scala/postgresql-testing",
+        "//libs-scala/scala-utils",
         "@maven//:ch_qos_logback_logback_classic",
         "@maven//:com_chuusai_shapeless_2_12",
         "@maven//:com_github_ghik_silencer_lib_2_12_11",

ledger-service/http-json/src/it/scala/http/HttpServiceIntegrationTest.scala

@@ -8,7 +8,7 @@ import java.nio.file.Files
 
 import akka.http.scaladsl.Http
 import akka.http.scaladsl.model.{HttpMethods, HttpRequest, StatusCodes, Uri}
-import com.daml.http.Statement.discard
+import com.daml.scalautil.Statement.discard
 import com.daml.http.util.TestUtil.writeToFile
 import org.scalacheck.Gen
 import org.scalatest.{Assertion, BeforeAndAfterAll}

ledger-service/http-json/src/it/scala/http/HttpServiceWithPostgresIntTest.scala

@@ -3,7 +3,7 @@
 
 package com.daml.http
 
-import com.daml.http.Statement.discard
+import com.daml.scalautil.Statement.discard
 import com.daml.testing.postgresql.PostgresAroundAll
 import spray.json.{JsString, JsValue}
 

ledger-service/http-json/src/main/scala/com/digitalasset/http/ContractsFetch.scala

@@ -17,7 +17,7 @@ import akka.stream.scaladsl.{
   Source,
 }
 import akka.stream.{ClosedShape, FanOutShape2, FlowShape, Graph, Materializer}
-import com.daml.http.Statement.discard
+import com.daml.scalautil.Statement.discard
 import com.daml.http.dbbackend.ContractDao.StaleOffsetException
 import com.daml.http.dbbackend.{ContractDao, Queries}
 import com.daml.http.dbbackend.Queries.{DBContract, SurrogateTpId}

ledger-service/http-json/src/main/scala/com/digitalasset/http/Endpoints.scala

@@ -19,7 +19,7 @@ import akka.util.ByteString
 import com.daml.lf
 import com.daml.http.ContractsService.SearchResult
 import com.daml.http.EndpointsCompanion._
-import com.daml.http.Statement.discard
+import com.daml.scalautil.Statement.discard
 import com.daml.http.domain.JwtPayload
 import com.daml.http.json._
 import com.daml.http.util.Collections.toNonEmptySet

ledger-service/http-json/src/main/scala/com/digitalasset/http/HttpService.scala

@@ -12,7 +12,7 @@ import akka.http.scaladsl.settings.ServerSettings
 import akka.stream.Materializer
 import com.daml.auth.TokenHolder
 import com.daml.grpc.adapter.ExecutionSequencerFactory
-import com.daml.http.Statement.discard
+import com.daml.scalautil.Statement.discard
 import com.daml.http.dbbackend.ContractDao
 import com.daml.http.json.{
   ApiValueToJsValueConverter,

ledger-service/http-json/src/main/scala/com/digitalasset/http/Main.scala

@@ -10,7 +10,7 @@ import akka.actor.ActorSystem
 import akka.http.scaladsl.Http.ServerBinding
 import akka.stream.Materializer
 import com.daml.grpc.adapter.{AkkaExecutionSequencerPool, ExecutionSequencerFactory}
-import com.daml.http.Statement.discard
+import com.daml.scalautil.Statement.discard
 import com.daml.http.dbbackend.ContractDao
 import com.daml.ledger.api.tls.TlsConfigurationCli
 import com.daml.ledger.api.refinements.ApiTypes.ApplicationId

ledger-service/http-json/src/main/scala/com/digitalasset/http/WebSocketService.scala

@@ -292,7 +292,7 @@ class WebSocketService(
     extends LazyLogging {
 
   import WebSocketService._
-  import Statement.discard
+  import com.daml.scalautil.Statement.discard
   import util.ErrorOps._
   import com.daml.http.json.JsonProtocol._
 

ledger-service/http-json/src/test/scala/com/digitalasset/http/json/JsonProtocolTest.scala

@@ -16,7 +16,7 @@ import com.daml.http.Generators.{
   genUnknownTemplateIds,
   genWarningsWrapper
 }
-import com.daml.http.Statement.discard
+import com.daml.scalautil.Statement.discard
 import com.daml.http.domain
 import org.scalacheck.Arbitrary.arbitrary
 import org.scalacheck.Gen.{identifier, listOf}

libs-scala/scala-utils/BUILD.bazel

@@ -0,0 +1,36 @@
+# Copyright (c) 2020 Digital Asset (Switzerland) GmbH and/or its affiliates. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+
+load(
+    "//bazel_tools:scala.bzl",
+    "da_scala_library",
+    "da_scala_test",
+    "lf_scalacopts",
+)
+
+scalacopts = lf_scalacopts + [
+    "-P:wartremover:traverser:org.wartremover.warts.NonUnitStatements",
+]
+
+da_scala_library(
+    name = "scala-utils",
+    srcs = glob(["src/main/scala/**/*.scala"]),
+    scalacopts = scalacopts,
+    tags = ["maven_coordinates=com.daml:scala-utils:__VERSION__"],
+    visibility = [
+        "//visibility:public",
+    ],
+    deps = [
+    ],
+)
+
+da_scala_test(
+    name = "test",
+    srcs = glob(["src/test/scala/**/*.scala"]),
+    scalacopts = scalacopts,
+    deps = [
+        ":scala-utils",
+        "//libs-scala/scalatest-utils",
+        "@maven//:org_scalaz_scalaz_core_2_12",
+    ],
+)

libs-scala/scala-utils/src/main/scala/com/daml/scalautil/Statement.scala

@@ -1,9 +1,16 @@
 // Copyright (c) 2020 Digital Asset (Switzerland) GmbH and/or its affiliates. All rights reserved.
 // SPDX-License-Identifier: Apache-2.0
 
-package com.daml.http
+package com.daml.scalautil
 
 object Statement {
+
+  /**
+    *  Suppresses `traverser:org.wartremover.warts.NonUnitStatements` warning on the expression level.
+    *
+    * @param evaluateForSideEffectOnly an expression with a side-effect that needs to be evaluated.
+    * @tparam A return type of the expression that gets discarded.
+    */
   @specialized def discard[A](evaluateForSideEffectOnly: A): Unit = {
     val _: A = evaluateForSideEffectOnly
     () //Return unit to prevent warning due to discarding value

libs-scala/scala-utils/src/test/scala/com/daml/scalautil/StatementSpec.scala

@@ -0,0 +1,40 @@
+// Copyright (c) 2020 Digital Asset (Switzerland) GmbH and/or its affiliates. All rights reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+package com.daml.scalautil
+
+import org.scalatest.{FlatSpec, Matchers}
+
+class StatementSpec extends FlatSpec with Matchers {
+  import com.daml.scalatest.Equalz._
+  import scalaz.std.anyVal._
+
+  behavior of Statement.getClass.getSimpleName
+
+  it should "evaluate passed expression for side effects" in {
+    var counter: Int = 0
+
+    def increment(): Int = {
+      counter += 1
+      counter
+    }
+
+    Statement.discard(increment()): Unit
+
+    Statement.discard {
+      counter += 1
+    }: Unit
+
+    counter shouldx equalz(2)
+  }
+
+  it should "not evaluate passed lambda expression" in {
+    var counter: Int = 0
+
+    Statement.discard { () =>
+      counter += 1
+    }
+
+    counter shouldx equalz(0)
+  }
+}

release/artifacts.yaml

@@ -149,3 +149,5 @@
   type: jar-scala
 - target: //libs-scala/build-info:build-info
   type: jar-scala
+- target: //libs-scala/scala-utils:scala-utils
+  type: jar-scala