[proposal] ScalacOption class based on types

lib/src/main/scala/org/typelevel/scalacoptions/proposal/ParseFailure.scala

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+/*
+ * Copyright 2022 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 org.typelevel.scalacoptions.proposal
+
+// TODO: TBD
+sealed abstract class ParseFailure
+
+object ParseFailure {}

lib/src/main/scala/org/typelevel/scalacoptions/proposal/ScalacOption.scala

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+/*
+ * Copyright 2022 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 org.typelevel.scalacoptions.proposal
+
+import org.typelevel.scalacoptions.ScalaVersion
+
+trait ScalacOption[A] {
+  type Type <: ScalacOption.Type
+
+  // ..or `isSupportedFor` maybe?
+  def isSupported(sv: ScalaVersion): Boolean
+
+  /** Base option name.
+    *
+    * @return
+    *   - for `"-deprecation"` results to `"deprecation"`
+    *   - for `"-deprecation:true"` results to `"deprecation"`
+    *   - for `"-Xlint"` results to `"Xlint"`
+    *   - for `"-Xlint:deprecation"` results to `"Xlint"`
+    */
+  def baseName: String
+
+  // /** Full option name.
+  //   *
+  //   * @return
+  //   *   - for `"-deprecation"` results to `"deprecation"`
+  //   *   - for `"-deprecation:true"` results to `"deprecation"` (same as above!)
+  //   *   - for `"-Xlint"` results to `"Xlint"`
+  //   *   - for `"-Xlint:deprecation"` results to `"Xlint:deprecation"`
+  //   */
+  // def fullName: String
+
+  /** Parses the option from a raw value found for the option's base name.
+    *
+    * @param rawValue
+    *   a raw option value, can be empty strings for options like `-deprecation`
+    *
+    * @return
+    *   - `None` if the value does not belong to the option and thus cannot be parsed, i.e. when
+    *     `"unused"` is passed where `-Xlint:deprecation` model is expected;
+    *   - `Some(A)` when a correct value is passed for the option, e.g. both `"unused"` and
+    *     `"-unused"` will be accepted for the an option type class that models the `-Xlint:unused`
+    *     option.
+    *
+    * @note
+    *   It deliberately made not returning any failure type like `ParseFailure`, becase
+    *   `ScalacOption.Select` is responsible for that.
+    */
+  def parse(rawValue: String): Option[A]
+}
+
+object ScalacOption {
+  type Aux[A, T <: Type] = ScalacOption[A] { type Type = T }
+
+  // Note: initially I thought that Singe/Recurring might not be necessary.
+  //       But later I realized that `Recurring` can be useful for modeling such options like "-Wconf"
+  sealed trait Type
+  abstract final class Single private ()    extends Type // never instantiated
+  abstract final class Recurring private () extends Type // never instantiated
+
+  sealed trait Select[A] {
+    // Not sure why it is a higher kinded type in http4s' Header.
+    // A regular plain type seems to be just enough here.
+    type Out
+
+    /** Parses all raw option values groupped by their [[ScalacOption.baseName]].
+      *
+      * @param rawValues
+      *   a list of raw option values in the order they occured in a command line.
+      */
+    def parse(rawValues: List[String]): Option[Out]
+  }
+
+  object Select {
+    implicit def singleScalacOption[A](implicit
+      so: ScalacOption.Aux[A, Single]
+    ): Select[A] { type Out = A } =
+      new Select[A] {
+        type Out = A
+
+        def parse(rawValues: List[String]): Option[A] = {
+          // Assume for now that for a single-occuring option the last value occured overrides
+          // all previous values. E.g.: for `Seq("-feature", "-feature:false")` the last one should
+          // take effect.
+          rawValues.iterator.flatMap(so.parse).toList.lastOption
+        }
+      }
+
+    implicit def recurringScalacOption[A](implicit
+      so: ScalacOption.Aux[A, Recurring]
+    ): Select[A] { type Out = List[A] } =
+      new Select[A] {
+        type Out = List[A] // consider NonEmptyList
+
+        def parse(rawValues: List[String]): Option[List[A]] = {
+          // As simple as it is (but with NonEmptyList it would be even simpler).
+          rawValues.iterator.flatMap(so.parse).toList match {
+            case Nil => None
+            case nel => Some(nel) // the result cannot be an empty list!
+          }
+        }
+      }
+  }
+}

lib/src/main/scala/org/typelevel/scalacoptions/proposal/ScalacOptions.scala

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+/*
+ * Copyright 2022 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 org.typelevel.scalacoptions.proposal
+
+/** A collection of scalac options.
+  *
+  * @param rawOptions
+  *   raw untyped scalac options groupped by their base name.
+  *
+  * @example
+  *   The following list of options:
+  *   {{{
+  *   Seq(
+  *     "-deprecation",
+  *     "-feature:false",
+  *     "-Xlint:deprecation,unused",
+  *     "-Wconf:cat=lint&msg=hello:e,any:i",
+  *     "-Xlint:_,-constant",
+  *     "-Wunused"
+  *   )
+  *   }}}
+  *   will be represented as:
+  *   {{{
+  *     Map(
+  *       "deprecation" -> List(""),
+  *       "feature" -> List("false"),
+  *       "Xlint" -> List("deprecation", "unused", "_", "-constant"),
+  *       "Wconf" -> List("msg=cat=lint&msg=hello", "any:i"),
+  *       "Wunused" -> List("")
+  *     )
+  *   }}}
+  *
+  * @note
+  *   Even a single option like `-Xlint` should be kept as a pair of `"Xlint" -> List("")`, because
+  *   it can be important to parse groupped options correctly. It means that the underlying list
+  *   cannot be empty. Thus, the question: can be consider `NonEmptyList` from cats for that?
+  */
+final class ScalacOptions(rawOptions: Map[String, List[String]]) {
+
+  def get[A](implicit opt: ScalacOption[A], sel: ScalacOption.Select[A]): Option[sel.Out] = {
+    rawOptions
+      .get(opt.baseName)
+      .flatMap { sel.parse(_) }
+  }
+}

lib/src/test/scala/org/typelevel/scalacoptions/proposal/ScalacOptionSuite.scala

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+/*
+ * Copyright 2022 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 org.typelevel.scalacoptions.proposal
+
+class ScalacOptionSuite {}

lib/src/test/scala/org/typelevel/scalacoptions/proposal/ScalacOptionsSuite.scala

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+/*
+ * Copyright 2022 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 org.typelevel.scalacoptions.proposal
+
+import org.scalacheck.Arbitrary
+import org.scalacheck.Gen
+import org.scalacheck.Prop
+import org.typelevel.scalacoptions.ScalaVersion
+
+class ScalacOptionsSuite extends munit.ScalaCheckSuite {
+  import ScalacOptionsSuite._
+
+  private val arbStrGen = Arbitrary.arbitrary[String]
+  // uncomment to simplify debugging
+  // TODO: remove!
+  // private val arbStrGen = Gen.asciiPrintableStr
+
+  test("ScalacOptions.get should work for ScalacOption.Single") {
+    val gen =
+      for {
+        targetBaseName    <- arbStrGen
+        targetResultValue <- arbStrGen
+        targetOtherValues <-
+          Gen.listOf(
+            Gen.oneOf(
+              arbStrGen,
+              arbStrGen.map(targetResultValue + _)
+            )
+          )
+        otherOptions <- Gen.mapOf(Gen.zip(arbStrGen, Gen.listOf(arbStrGen)))
+      } yield {
+        (
+          targetBaseName,
+          targetResultValue,
+          otherOptions + (targetBaseName -> (targetOtherValues :+ targetResultValue))
+        )
+      }
+
+    Prop.forAll(gen) { case (targetBaseName, targetResultValue, allOptions) =>
+      implicit val singleScalacOption: ScalacOption.Aux[TestOption, ScalacOption.Single] =
+        new ScalacOption[TestOption] {
+          type Type = ScalacOption.Single
+
+          override def isSupported(sv: ScalaVersion): Boolean = ??? // not a subject for testing
+
+          override def baseName: String = targetBaseName
+
+          override def parse(rawValue: String): Option[TestOption] = {
+            if (rawValue.startsWith(targetResultValue))
+              Some(TestOption(rawValue))
+            else
+              None
+          }
+        }
+
+      val obtained = new ScalacOptions(allOptions).get[TestOption].map(_.value)
+
+      assertEquals(obtained, Some(targetResultValue))
+    }
+  }
+}
+
+object ScalacOptionsSuite {
+  final case class TestOption(value: String) extends AnyVal
+}