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Sep 17, 2025
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Update the nightlies doc #3213

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Update the nightlies doc to mention repo.scala-lang.org
Gedochao Sep 16, 2025
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Update _overviews/core/nightlies.md
Gedochao Sep 17, 2025
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99 changes: 54 additions & 45 deletions _overviews/core/nightlies.md
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Expand Up @@ -8,80 +8,89 @@ We regularly publish nightly versions of both Scala 3 and 2 so that users can pr

Here's how to find and use these versions.

## Scala 3
## General information on nightlies

Scala 3 nightly versions are published to Maven Central. If you know the full version number of the nightly you want to use, you can use it just like any other Scala 3 version.
### Scala 3

One quick way to get that version number is to visit [https://dotty.epfl.ch](https://dotty.epfl.ch) and look in the upper left corner.
Scala 3 nightly versions are published to [https://repo.scala-lang.org](https://repo.scala-lang.org). Historically, they used to be published to Maven Central. Old nightly versions of Scala 3 (all the way until `3.8.0-RC1-bin-20250822-658c8bd-NIGHTLY` in August 2025) are still available there, as well as via [https://repo.scala-lang.org](https://repo.scala-lang.org).

Another way is to scrape Maven Central, as shown in this script: [https://raw.githubusercontent.com/VirtusLab/community-build3/master/scripts/lastVersionNightly.sc](https://raw.githubusercontent.com/VirtusLab/community-build3/master/scripts/lastVersionNightly.sc)
If you know the full version number of the nightly you want to use, you can use it just like any other Scala 3 version.

A third way is to use [scala-cli](https://scala-cli.virtuslab.org), as follows. (Since Scala 3.5.0, the `scala` command runs `scala-cli`.)
There are a number of ways to get that version number, as listed below.

### scala-cli
### Scala 2

You can run nightlies with commands such as:

scala-cli -S 3.nightly
scala-cli -S 3.3.nightly

The default command is `repl`, but all the other scala-cli subcommands such as `compile` and `run` work, too. It also works with `//>` directives in your script itself, for example:
We informally refer to Scala 2 “nightly” versions, but technically it's a misnomer. A so-called “nightly” is built for every merged PR in the Scala 2 repo.

//> using scala 3.nightly

See this [scala-cli doc page](https://scala-cli.virtuslab.org/docs/commands/compile#scala-nightlies) for details.
Similarly to Scala 3 nightlies, they are available at [https://repo.scala-lang.org/artifactory/maven-nightlies](https://repo.scala-lang.org/artifactory/maven-nightlies).

## Scala 2.13 or 2.12
## How to use nightly versions

We informally refer to Scala 2 “nightly” versions, but technically it's a misnomer. A so-called “nightly” is built for every merged PR.
### Scala CLI

Scala 2 nightly versions are published to a special resolver. Unless you are using scala-cli, you'll need to add that resolver to your build configuration in order to use these versions.
Scala CLI is the official runner of the language and has nightlies available without any extra configuration. From Scala 3.5.0 and on it's available under the `scala` command in Scala 3 installations. It can also be installed separately as `scala-cli`.

### quick version (sbt)
Note: The nightly repository is supported since Scala CLI v1.9.0 onwards (or `scala` installed with Scala 3.7.3 or newer).

Global / resolvers += "scala-integration" at
"https://scala-ci.typesafe.com/artifactory/scala-integration/"
scalaVersion := "2.13.15-bin-abcd123"
You can run nightlies with commands such as:

For a 2.12 nightly, substitute e.g. `2.12.20` for `2.13.15`; in either case, it's the version number of the _next_ release on that branch.
scala -e 'println("Hello") -S 3.nightly
scala -e 'println("Hello") -S 3.3.nightly
scala -e 'println("Hello") -S 2.13.nightly
scala -e 'println("Hello") -S 2.nightly # same as 2.13.nightly
scala -e 'println("Hello") -S 2.12.nightly

For `abcd123`, substitute the first 7 characters of the SHA of the latest commit to the [2.13.x branch](https://github.com/scala/scala/commits/2.13.x) or [2.12.x branch](https://github.com/scala/scala/commits/2.12.x) that has a green checkmark. (Clicking the checkmark will show a CI job name with the whole version in its name.)
The default command is `repl` (unless sources are passed, in which case it switches to `run`), but all the other scala-cli subcommands such as `compile` and `run` work, too. It also works with `//> using` directives in your script itself, for example:

A quick way to find out the full version number of a current nightly is to use [scala-cli](https://scala-cli.virtuslab.org), as follows.
//> using scala 3.nightly
//> using scala 3.3.nightly
//> using scala 2.nightly
//> using scala 2.13.nightly
//> using scala 2.12.nightly

### quick version (scala-cli)
See this [scala-cli doc page](https://scala-cli.virtuslab.org/docs/commands/compile#scala-nightlies) for details.

You can run nightlies with:
### Get it from the nightly website

scala-cli -S 2.13.nightly
scala-cli -S 2.nightly # same as 2.13.nightly
scala-cli -S 2.12.nightly
A quick way to get that version number is to visit [https://nightly.scala-lang.org](https://nightly.scala-lang.org) and look in the upper left corner.

The default command is `repl`, but all the other scala-cli subcommands such as `compile` and `run` work, too. It also works with `//>` directives in your script itself, for example:
### Check the repository, directly

//> using scala 2.nightly
Another way is to scrape the repository, as shown in this script: [https://raw.githubusercontent.com/VirtusLab/community-build3/master/scripts/lastVersionNightly.sc](https://raw.githubusercontent.com/VirtusLab/community-build3/master/scripts/lastVersionNightly.sc)

### Longer explanation
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the Longer explanation section feels redundant now, at least for the scope of this document, so I ended up removing it.
repo.scala-lang.org proxies to Scala 2 nightlies, so that part is basically an implementation detail.
Let me know if we want to preserve it somewhere.
cc @SethTisue @lrytz

### SBT

We no longer publish `-SNAPSHOT` versions of Scala 2.
To use recent nightlies with SBT, adding the appropriate resolver to the build configuration is necessary.

But the team does publish nightly versions, each with its own fixed version number. The version number of a nightly looks like e.g. `2.13.1-bin-abcd123`. (`-bin-` signals binary compatibility to sbt; all 2.13.x releases since 2.13.0 are binary compatible with each other.)
ThisBuild / scalaVersion := "3.8.0-RC1-bin-20250916-eb1bb73-NIGHTLY"
ThisBuild / resolvers += Resolver.scalaNightlyRepository
lazy val root = (project in file("."))
.settings(name := "sbt-with-scala-nightlies")

To tell sbt to use one of these nightlies, you need to do three things.
Also note that SBT 1.11.5 or newer is necessary.

First, add the resolver where the nightlies are kept:
### Mill

Global / resolvers += "scala-integration" at
"https://scala-ci.typesafe.com/artifactory/scala-integration/"
To use recent nightlies with Mill, a custom resolver for the initial bootstrap of the build is needed.
Here's an example `build.mill` file:

Second, specify the Scala version:
package build
import mill.*
import mill.api.*
import scalalib.*

scalaVersion := "2.13.1-bin-abcd123"
def scalaNightlyRepo = "https://repo.scala-lang.org/artifactory/maven-nightlies"

But that isn't a real version number. Manually substitute a version number containing the 7-character SHA of the last commit in the [scala/scala repository](https://github.com/scala/scala) for which a nightly version was published. Look at [https://travis-ci.org/scala/scala/branches](https://travis-ci.org/scala/scala/branches) and you'll see the SHA in the upper right corner of the 2.13.x (or 2.12.x) section.
object project extends ScalaModule {
def jvmWorker = ModuleRef(CustomJvmWorkerModule)
override def scalaVersion = "3.8.0-RC1-bin-20250916-eb1bb73-NIGHTLY"
override def repositories = Task { super.repositories() ++ Seq(scalaNightlyRepo)}
}

As soon as 2.13.1 is released, the version number in the nightly will bump to 2.13.2, and so on.
object CustomJvmWorkerModule extends JvmWorkerModule, CoursierModule {
override def repositories = Task { super.repositories() ++ Seq(scalaNightlyRepo)}
}

If you have a multiproject build, be sure you set these settings across all projects when you modify your build definition. Or, you may set them temporarily in the sbt shell with `++2.13.1-bin-abcd123` (sbt 0.13.x) or `++2.13.1-bin-abcd123!` (sbt 1.x; the added exclamation point is necessary to force a version not included in `crossScalaVersions` to be used).
Note how the custom `JvmWorkerModule` is necessary with the added repository. It is not enough to just define it as a repository for the module dependencies.

Ideally, we would suggest an automated way to ask Travis-CI for the right SHA. This is presumably possible via Travis-CI's API, but as far as we know, nobody has looked into it yet. (Is there a volunteer?)
Also note that Mill 1.0.5 or newer is necessary for this.