Add _assert

This is an assertion, which can be disabled at build time.
For now, it is not disabled by default. For now, it is
also unused.

build.sbt

@@ -94,6 +94,9 @@ ThisBuild / scalaOrganization := "org.scala-lang"
 ThisBuild / evictionErrorLevel := Level.Warn
 ThisBuild / semanticdbEnabled := true
 
+val assertionsEnabled = settingKey[Boolean]("Whether to compile `_assert` calls")
+ThisBuild / assertionsEnabled := !java.lang.Boolean.getBoolean("dev.tauri.choam.build.disableAssertions")
+
 ThisBuild / tlBaseVersion := "0.4"
 ThisBuild / tlUntaggedAreSnapshots := false // => we get versions like 0.4-39d987a
 ThisBuild / tlJdkRelease := Some(11)
@@ -339,13 +342,17 @@ lazy val skiplist = crossProject(JVMPlatform, JSPlatform)
   .in(file("skiplist"))
   .settings(name := "choam-skiplist")
   .disablePlugins(disabledPlugins: _*)
+  .enablePlugins(BuildInfoPlugin)
   .settings(commonSettings)
   .jvmSettings(commonSettingsJvm)
   .jsSettings(commonSettingsJs)
-  .settings(libraryDependencies ++= Seq(
-    dependencies.catsKernel.value,
-    dependencies.catsScalacheck.value % TestInternal,
-  ))
+  .settings(buildInfoSettings(pkg = "dev.tauri.choam.internal"))
+  .settings(
+    libraryDependencies ++= Seq(
+      dependencies.catsKernel.value,
+      dependencies.catsScalacheck.value % TestInternal,
+    ),
+  )
 
 lazy val data = crossProject(JVMPlatform, JSPlatform)
   .crossType(CrossType.Full)
@@ -445,11 +452,15 @@ lazy val ce = crossProject(JVMPlatform, JSPlatform)
 /** Internal use only; no published project may depend on this */
 lazy val internalHelpers = project.in(file("internal-helpers"))
   .settings(name := "choam-internal-helpers")
-  .enablePlugins(NoPublishPlugin)
+  .enablePlugins(NoPublishPlugin, BuildInfoPlugin)
   .disablePlugins(disabledPlugins: _*)
   .settings(commonSettings)
   .settings(commonSettingsJvm)
+  .settings(buildInfoSettings(pkg = "dev.tauri.choam.helpers"))
   .dependsOn(ce.jvm % "compile->compile;test->test")
+  .settings(
+    assertionsEnabled := false, // so that we can test that they're disabled
+  )
 
 lazy val laws = crossProject(JVMPlatform, JSPlatform)
   .crossType(CrossType.Full)
@@ -703,7 +714,6 @@ lazy val commonSettingsJs = Seq[Setting[_]](
 lazy val commonSettings = Seq[Setting[_]](
   scalacOptions ++= Seq(
     "-language:higherKinds",
-    // TODO: "-Xelide-below", "INFO",
     // TODO: experiment with -Ydelambdafy:inline for performance
     // TODO: experiment with -Yno-predef and/or -Yno-imports
   ),
@@ -719,7 +729,7 @@ lazy val commonSettings = Seq[Setting[_]](
         "-Xsource:3-cross",
         "-Wnonunit-statement",
         "-Wvalue-discard",
-      )
+      ) ++ (if (assertionsEnabled.value) Nil else List("-Xelide-below", "2001"))
     } else {
       // 3.x:
       List(
@@ -787,6 +797,17 @@ lazy val commonSettings = Seq[Setting[_]](
   inTask(packageDoc)(extraPackagingSettings)
 ) ++ publishSettings
 
+def buildInfoSettings(pkg: String): Seq[Setting[_]] = Seq(
+  buildInfoPackage := pkg,
+  buildInfoKeys := Seq(
+    assertionsEnabled,
+  ),
+  buildInfoOptions ++= Seq(
+    BuildInfoOption.PackagePrivate,
+    BuildInfoOption.ConstantValue,
+  ),
+)
+
 lazy val publishSettings = Seq[Setting[_]](
   organization := "dev.tauri",
   organizationHomepage := Some(url("https://tauri.dev")),

core/shared/src/main/scala/dev/tauri/choam/package.scala

@@ -17,7 +17,7 @@
 
 package dev.tauri
 
-package object choam {
+package object choam extends internal.ChoamUtils {
 
   private[choam] type tailrec = scala.annotation.tailrec
 

core/shared/src/test/scala/dev/tauri/choam/core/AssertSpec.scala

@@ -0,0 +1,26 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ * Copyright 2016-2024 Daniel Urban and contributors listed in NOTICE.txt
+ *
+ * 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 dev.tauri.choam
+package core
+
+final class AssertSpec extends BaseSpec {
+
+  test("_assert should be enabled during tests (for now)".fail) {
+    _assert(false)
+  }
+}

internal-helpers/src/test/scala-2.13/dev/tauri/choam/helpers/ChoamUtils2.scala

@@ -0,0 +1,34 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ * Copyright 2016-2024 Daniel Urban and contributors listed in NOTICE.txt
+ *
+ * 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 dev.tauri.choam
+package helpers
+
+import scala.annotation.{ elidable, nowarn }
+
+// Note: this is duplicated from `ChoamUtils`,
+// so that we can test disabling `_assert`.
+@nowarn("msg=elidable")
+private[choam] abstract class ChoamUtils2 {
+
+  @elidable(elidable.ASSERTION)
+  private[choam] final def _assert(ok: Boolean): Unit = {
+    if (!ok) {
+      throw new AssertionError
+    }
+  }
+}

internal-helpers/src/test/scala-2.13/dev/tauri/choam/helpers/DisableAssertionsSpecScala213.scala

@@ -0,0 +1,27 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ * Copyright 2016-2024 Daniel Urban and contributors listed in NOTICE.txt
+ *
+ * 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 dev.tauri.choam
+package helpers
+
+final class DisableAssertionsSpecScala213 extends BaseSpec {
+
+  test("The Scala 2.13 `-Xelide-below` also affects Predef.assert") {
+    Predef.assert(false)
+    Predef.assert(false, "foo")
+  }
+}

internal-helpers/src/test/scala-3/dev/tauri/choam/helpers/ChoamUtils2.scala

@@ -0,0 +1,35 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ * Copyright 2016-2024 Daniel Urban and contributors listed in NOTICE.txt
+ *
+ * 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 dev.tauri.choam
+package helpers
+
+// Note: this is duplicated from `ChoamUtils`,
+// so that we can test disabling `_assert`.
+private[choam] abstract class ChoamUtils2 {
+
+  private[choam] inline final val assertionsEnabled =
+    BuildInfo.assertionsEnabled
+
+  private[choam] inline final def _assert(inline ok: Boolean): Unit = {
+    inline if (assertionsEnabled) {
+      if (!ok) {
+        throw new AssertionError
+      }
+    }
+  }
+}

internal-helpers/src/test/scala/dev/tauri/choam/helpers/DisabledAssertionsSpec.scala

@@ -0,0 +1,43 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ * Copyright 2016-2024 Daniel Urban and contributors listed in NOTICE.txt
+ *
+ * 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 dev.tauri.choam
+package helpers
+
+final class DisableAssertionsSpec extends BaseSpec {
+
+  test("_assert should have no effect") {
+    _assert(false)
+    _assert({ throw new Exception; false }) : @nowarn("cat=w-flag-dead-code")
+  }
+
+  test("munit assert should still work".fail) {
+    this.assert(false)
+  }
+
+  test("require(Boolean) should still work".fail) {
+    require(false)
+  }
+
+  test("require(Boolean, => Any) should still work".fail) {
+    require(false, "foo")
+  }
+
+  test("impossible should still work".fail) {
+    impossible("foo")
+  }
+}

internal-helpers/src/test/scala/dev/tauri/choam/helpers/package.scala

@@ -0,0 +1,20 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ * Copyright 2016-2024 Daniel Urban and contributors listed in NOTICE.txt
+ *
+ * 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 dev.tauri.choam
+
+package object helpers extends ChoamUtils2

mcas/shared/src/main/scala/dev/tauri/choam/internal/mcas/package.scala

@@ -18,7 +18,7 @@
 package dev.tauri.choam
 package internal
 
-package object mcas {
+package object mcas extends ChoamUtils {
 
   private[mcas] type tailrec = scala.annotation.tailrec
 

mcas/shared/src/test/scala/dev/tauri/choam/internal/mcas/AssertSpec.scala

@@ -0,0 +1,27 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ * Copyright 2016-2024 Daniel Urban and contributors listed in NOTICE.txt
+ *
+ * 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 dev.tauri.choam
+package internal
+package mcas
+
+final class AssertSpec extends BaseSpec {
+
+  test("_assert should be enabled during tests (for now)".fail) {
+    _assert(false)
+  }
+}

project/plugins.sbt

@@ -37,5 +37,6 @@ addSbtPlugin("org.portable-scala" % "sbt-scalajs-crossproject" % "1.3.2") // htt
 addSbtPlugin("org.scala-js" % "sbt-scalajs" % "1.17.0") // https://www.scala-js.org/
 addSbtPlugin("net.bzzt" % "sbt-strict-scala-versions" % "0.0.1") // https://github.com/raboof/sbt-strict-scala-versions
 addSbtPlugin("com.github.sbt" % "sbt-native-packager" % "1.10.4") // https://github.com/sbt/sbt-native-packager
+addSbtPlugin("com.eed3si9n" % "sbt-buildinfo" % "0.13.1") // https://github.com/sbt/sbt-buildinfo
 
 ThisBuild / semanticdbEnabled := true

skiplist/jvm/src/test/scala/dev/tauri/choam/internal/skiplist/AssertSpec.scala

@@ -0,0 +1,27 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ * Copyright 2016-2024 Daniel Urban and contributors listed in NOTICE.txt
+ *
+ * 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 dev.tauri.choam
+package internal
+package skiplist
+
+final class AssertSpec extends munit.FunSuite {
+
+  test("_assert should be enabled during tests (for now)".fail) {
+    _assert(false)
+  }
+}

skiplist/shared/src/main/scala-2.13/dev/tauri/choam/internal/ChoamUtils.scala

@@ -0,0 +1,33 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ * Copyright 2016-2024 Daniel Urban and contributors listed in NOTICE.txt
+ *
+ * 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 dev.tauri.choam
+package internal
+
+import scala.annotation.{ elidable, nowarn }
+
+// Note: this code is duplicated for (1) Scala 2.13/3, and (2) for tests in `helpers`.
+@nowarn("msg=elidable")
+private[choam] abstract class ChoamUtils {
+
+  @elidable(elidable.ASSERTION)
+  private[choam] final def _assert(ok: Boolean): Unit = {
+    if (!ok) {
+      throw new AssertionError
+    }
+  }
+}