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Update and correct macro cross tutorial #3031

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Update and correct macro cross tutorial #3031

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31 changes: 16 additions & 15 deletions _overviews/scala3-migration/tutorial-macro-cross-building.md
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Original file line number Diff line number Diff line change
Expand Up @@ -24,10 +24,11 @@ In order to exemplify this tutorial, we will consider the minimal macro library
lazy val example = project
.in(file("example"))
.settings(
scalaVersion := "2.13.11",
scalaVersion := "2.13.14",
libraryDependencies ++= Seq(
"org.scala-lang" % "scala-reflect" % scalaVersion.value
)
"org.scala-lang" % "scala-reflect" % scalaVersion.value,
"org.scalameta" %% "munit" % "1.0.0" % Test,
),
)
```

Expand All @@ -45,7 +46,7 @@ case class Location(path: String, line: Int)
object Macros {
def location: Location = macro locationImpl

private def locationImpl(c: Context): c.Tree = {
def locationImpl(c: Context): c.Tree = {
import c.universe._
val location = typeOf[Location]
val line = Literal(Constant(c.enclosingPosition.line))
Expand Down Expand Up @@ -73,11 +74,11 @@ The main idea is to build the artifact twice and to publish two releases:
You can add Scala 3 to the list of `crossScalaVersions` of your project:

```scala
crossScalaVersions := Seq("2.13.11", "3.3.1")
crossScalaVersions := Seq("2.13.14", "3.3.3")
```

The `scala-reflect` dependency won't be useful in Scala 3.
Remove it conditionally with something like:
Add it conditionally under Scala 2 with something like:

```scala
// build.sbt
Expand All @@ -91,15 +92,15 @@ libraryDependencies ++= {
}
```

After reloading sbt, you can switch to the Scala 3 context by running `++3.3.1`.
At any point you can go back to the Scala 2.13 context by running `++2.13.11`.
After reloading sbt, you can switch to the Scala 3 context by running `++3.3.3`.
At any point you can go back to the Scala 2.13 context by running `++2.13.14`.

## 2. Rearrange the code in version-specific source directories

If you try to compile with Scala 3 you should see some errors of the same kind as:

{% highlight text %}
sbt:example> ++3.3.1
sbt:example> ++3.3.3
sbt:example> example / compile
[error] -- Error: /example/src/main/scala/location/Location.scala:15:35
[error] 15 | val location = typeOf[Location]
Expand Down Expand Up @@ -143,7 +144,7 @@ import scala.language.experimental.macros
object Macros {
def location: Location = macro locationImpl

private def locationImpl(c: Context): c.Tree = {
def locationImpl(c: Context): c.Tree = {
import c.universe._
val location = typeOf[Location]
val line = Literal(Constant(c.enclosingPosition.line))
Expand All @@ -156,7 +157,7 @@ object Macros {
{% endtabs %}

Now we can initialize each of our Scala 3 macro definitions in the `src/main/scala-3` folder.
They must have the exact same signature than their Scala 2.13 counterparts.
They must have the exact same signature as their Scala 2.13 counterparts.

{% tabs scala-3-location_1 %}
{% tab 'Scala 3 Only' %}
Expand Down Expand Up @@ -191,9 +192,9 @@ object Macros:
private def locationImpl(using quotes: Quotes): Expr[Location] =
import quotes.reflect.Position
val pos = Position.ofMacroExpansion
val file = Expr(pos.sourceFile.jpath.toString)
val path = Expr(pos.sourceFile.path)
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They preferred getJPath.getOrElse on the related PR. But I think source must have a path, but may not have a file. A source must have a path because I need to be able to report errors at a location, even if the location is virtual. It's not a Scala thing but an API thing.

val line = Expr(pos.startLine + 1)
'{new Location($file, $line)}
'{new Location($path, $line)}
```
{% endtab %}
{% endtabs %}
Expand Down Expand Up @@ -222,13 +223,13 @@ class MacrosSpec extends munit.FunSuite {
You should now be able to run the tests in both versions.

{% highlight text %}
sbt:example> ++2.13.11
sbt:example> ++2.13.14
sbt:example> example / test
location.MacrosSpec:
+ location
[info] Passed: Total 1, Failed 0, Errors 0, Passed 1
[success]
sbt:example> ++3.3.1
sbt:example> ++3.3.3
sbt:example> example / test
location.MacrosSpec:
+ location
Expand Down
4 changes: 2 additions & 2 deletions _overviews/scala3-migration/tutorial-macro-mixing.md
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Expand Up @@ -67,9 +67,9 @@ object Macros:

private def locationImpl(using quotes: Quotes): Expr[Location] =
import quotes.reflect.Position
val file = Expr(Position.ofMacroExpansion.sourceFile.jpath.toString)
val path = Expr(Position.ofMacroExpansion.sourceFile.path)
val line = Expr(Position.ofMacroExpansion.startLine + 1)
'{new Location($file, $line)}
'{new Location($path, $line)}
```
{% endtab %}
{% endtabs %}
Expand Down
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