Scala 3 #143

tpolecat · 2021-05-04T21:03:37Z

resolves #104

This adds a cross-build for Scala 3.0.0.

Removed sbt-gsp (which doesn't work with Scala 3) and inlined the necessary settings.
Added version-dependent Circe dependencies, with 0.13 for Scala 2 and 0.14 for Scala 3. They are not compatible and forcing Scala 2 people to use Circe 0.14 would likely break things. We can revisit this when things settle down a bit.
Removed the dependency on circe-optics, which doesn't exist for Scala 3. Workaround is JsonExtractors and a bit of ACursor bumbling in the tests.
The inability to have a term of type Codec[_] forced me to write ExistentialCodec which pushes the type parameter down into a type member. The Anti-Aux pattern.
generic is ported as-is, with all sources under scala-2 an publishing disabled for Scala 3. We can add Scala 3 support in a followup PR.

TODO:

enable demo (http4s is available now)

tpolecat · 2021-05-05T17:31:44Z

modules/core/src/main/scala/compiler.scala

-      val q = parseSelections(sels, None, fragments)
-      val vs = vds.map {
-        case VariableDefinition(nme, tpe, _) => UntypedVarDef(nme.value, tpe, None)
+  def parseOperation(op: Operation, fragments: Map[String, FragmentDefinition]): Result[UntypedOperation] = {


Scala 3 warns that this single-case match would only fail with case null => so I collapsed it to a destructuring assignment. There are a few more of these.

tpolecat · 2021-05-05T17:32:28Z

modules/core/src/main/scala/jsonextractors.scala

+import io.circe.Json
+import io.circe.JsonObject
+
+object JsonExtractor {


Because circe-optics doesn't exist for Scala 3 [yet].

tpolecat · 2021-05-05T17:33:13Z

modules/core/src/main/scala/predicate.scala

@@ -21,7 +21,7 @@ import QueryInterpreter.mkErrorResult
 * we need to be able to construct where clauses from predicates over fields/attributes), so
 * these cannot be arbitrary functions `Cursor => Boolean`.
 */
-trait Term[T] extends Product with Serializable {
+trait Term[T] extends Product with Serializable { // fun fact: making this covariant crashes Scala 3


Because Term[+T] crashes Scala 3 there are some upcasts to Term[Any] later on.

tpolecat · 2021-05-05T17:34:32Z

modules/core/src/main/scala/predicate.scala

-      c.flatListPath(path).map(_.map { case ScalarFocus(f: T @unchecked) => f })
+      c.flatListPath(path).map(_.map {
+        case ScalarFocus(f: T @unchecked) => f
+        case _ => sys.error("impossible")


The exhaustiveness checker is a lot better so I needed to add a few of these. All these cases should be impossible but maybe the error messages could be better. What do you think?

tpolecat · 2021-05-05T17:35:22Z

modules/core/src/main/scala/queryinterpreter.scala

@@ -170,7 +170,7 @@ class QueryInterpreter[F[_]](mapping: Mapping[F]) {
            case Ior.Right(elem) => (errors, elem :: elems)
            case Ior.Both(errs, elem) => (errs.toChain ++ errors, elem :: elems)
          }
-      }).map(_.reverse)
+      }).fmap(_.reverse)


Functor .map syntax doesn't work for tuples in Scala 3 because there's polymorphic map on Tuple now.

tpolecat · 2021-05-05T17:36:48Z

modules/core/src/main/scala/schema.scala

@@ -630,7 +630,7 @@ case class NullableType(
 *
 * @see https://facebook.github.io/graphql/draft/#sec-The-__Field-Type
 */
-case class Field private(
+case class Field(


We're calling this from a place that Scala 2 allows but Scala 3 doesn't. I don't think it needs to be private anyway.

tpolecat · 2021-05-05T17:38:14Z

modules/core/src/test/scala/compiler/Environment.scala

 // For license information see LICENSE or https://opensource.org/licenses/BSD-3-Clause

 package compiler

 import cats.Id
 import cats.implicits._
+import cats.catsInstancesForId


Scala 3 can't find instances for cats.Id but it's not clear why. This fixes it.

tpolecat · 2021-05-05T17:40:02Z

modules/doobie/src/main/scala/DoobieMapping.scala


 abstract class DoobieMapping[F[_]: Sync](
  val transactor: Transactor[F],
  val monitor:    DoobieMonitor[F]
 ) extends SqlMapping[F] {

  type Codec[A]   = (Meta[A], Boolean)
-  type Encoder[A] = (Put[A], Boolean)
+  type Encoder[-A] = (Put[A], Boolean) @uncheckedVariance


See SqlModule for more on this.

tpolecat · 2021-05-05T17:41:45Z

modules/sql/src/main/scala/SqlMapping.scala

@@ -190,7 +190,7 @@ trait SqlMapping[F[_]] extends CirceMapping[F] with SqlModule[F] { self =>
  final class MappedQuery(
    table: String,
    columns: List[ColumnRef],
-    metas: List[(Boolean, Codec[_])],
+    metas: List[(Boolean, ExistentialCodec)],


ExistentialCodec is defined in SqlModule, see below.

tpolecat · 2021-05-05T17:43:12Z

modules/sql/src/main/scala/SqlModule.scala

@@ -14,8 +14,24 @@ trait SqlModule[F[_]] {
  /** The type of a codec that reads and writes column values of type `A`. */
  type Codec[A]

+  /** A codec that has forgotten its type argument. */


Codec[_] isn't a type in Scala 3 so we have to push the existential down into a type member.

tpolecat · 2021-05-05T17:44:24Z

modules/sql/src/main/scala/SqlModule.scala

  /** The type of an encoder that writes column values of type `A`. */
-  type Encoder[A]
+  type Encoder[-A]


If Encoder is invariant there are one million pages of type errors in MappedQuery. Scala 2 is happy to crush stuff to Any after a while but Scala 3 keeps up and doesn't like what's happening in calls to loop(...).

tpolecat · 2021-05-07T14:56:27Z

build.sbt

-      "io.circe"          %% "circe-core"             % circeVersion,
-      "io.circe"          %% "circe-optics"           % circeOpticsVersion,
-      "io.circe"          %% "circe-parser"           % circeVersion
-    )


These dependencies all arrive transitively so I removed them as a simplification. Same in a few places below.

tpolecat · 2021-05-07T14:57:17Z

docs/src/main/paradox/tutorial/in-memory-model.md

@@ -193,7 +193,7 @@ Here the root of the result is "Luke Skywalker" and we loop back to Luke through
 The data type is not itself recursive, instead friend are identified by their ids. When traversing through the list of
 friends the `resolveFriends` method is used to locate the next `Character` value to visit.


No idea why this is being rendered in red.

tpolecat · 2021-05-07T14:57:38Z

modules/circe/src/test/scala/CirceData.scala

@@ -5,6 +5,7 @@ package edu.gemini.grackle
 package circetests

 import cats.Id
+import cats.catsInstancesForId


These instances are unavailable in Scala 3. I don't know why.

tpolecat · 2021-05-07T14:58:51Z

modules/core/src/main/scala/parser.scala

@@ -189,7 +189,7 @@ object GraphQLParser {
    QueryShorthand.widen[Ast.OperationDefinition] | Operation.widen

  lazy val QueryShorthand: Parser[Ast.OperationDefinition.QueryShorthand] =
-    SelectionSet.map(Ast.OperationDefinition.QueryShorthand)
+    SelectionSet.map(Ast.OperationDefinition.QueryShorthand.apply)


Scala 3 warns that apply-insertion is deprecated. I guess the companions no longer extend function types?

milessabin

LGTM!

tpolecat · 2021-05-10T15:56:41Z

Waiting on test-containers, which is having some issues. testcontainers/testcontainers-scala#177

tpolecat · 2021-05-25T14:28:58Z

test-containers is fixed, now waiting on cats-testkit-scalatest

tpolecat · 2021-05-25T14:30:37Z

(updated to 3.0.0 final)

tpolecat · 2021-05-25T17:23:09Z

Squashing since most commits don't build.

tpolecat added 4 commits May 4, 2021 14:37

core

dcdda29

circe

e2b8ce6

headerCreate doesn't work

1d0fd4c

sql, doobie

1cdb7d1

tpolecat commented May 5, 2021

View reviewed changes

tpolecat added 7 commits May 6, 2021 09:20

undo header update

a873ca1

undo header update

08592d4

skunk

aed947b

generic

e37a484

demo

878ee84

move off doobie shapshot

f49310b

docs

c044b34

tpolecat commented May 7, 2021

View reviewed changes

tpolecat marked this pull request as ready for review May 7, 2021 15:06

tpolecat requested a review from milessabin May 7, 2021 15:06

tpolecat changed the title ~~WIP: Scala 3~~ Scala 3 May 7, 2021

milessabin approved these changes May 7, 2021

View reviewed changes

scala 3.0 final

26e0d5c

tpolecat added 2 commits May 25, 2021 10:50

re-enable demo

e3a73b9

update doobie

ac97040

tpolecat merged commit fd9f78a into main May 25, 2021

tpolecat deleted the scala-3 branch May 25, 2021 17:23

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Scala 3 #143

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tpolecat commented May 25, 2021

		@@ -193,7 +193,7 @@ Here the root of the result is "Luke Skywalker" and we loop back to Luke through
		The data type is not itself recursive, instead friend are identified by their ids. When traversing through the list of
		friends the `resolveFriends` method is used to locate the next `Character` value to visit.

Scala 3 #143

Scala 3 #143

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