Add --offline option

modules/build/src/main/scala/scala/build/compiler/BloopCompilerMaker.scala

@@ -4,20 +4,23 @@ import bloop.rifle.{BloopRifleConfig, BloopServer, BloopThreads}
 import ch.epfl.scala.bsp4j.BuildClient
 
 import scala.build.Logger
+import scala.build.errors.FetchingDependenciesError
 import scala.build.internal.Constants
 import scala.concurrent.duration.DurationInt
+import scala.util.Try
 
 final class BloopCompilerMaker(
   config: BloopRifleConfig,
   threads: BloopThreads,
-  strictBloopJsonCheck: Boolean
+  strictBloopJsonCheck: Boolean,
+  offline: Boolean
 ) extends ScalaCompilerMaker {
   def create(
     workspace: os.Path,
     classesDir: os.Path,
     buildClient: BuildClient,
     logger: Logger
-  ): BloopCompiler = {
+  ): ScalaCompiler = {
     val createBuildServer =
       () =>
         BloopServer.buildServer(
@@ -30,6 +33,20 @@ final class BloopCompilerMaker(
           threads,
           logger.bloopRifleLogger
         )
-    new BloopCompiler(createBuildServer, 20.seconds, strictBloopJsonCheck)
+
+    Try(new BloopCompiler(createBuildServer, 20.seconds, strictBloopJsonCheck))
+      .toEither
+      .left.flatMap {
+        case e if offline =>
+          e.getCause match
+            case _: FetchingDependenciesError =>
+              logger.debug("Couldn't fetch Bloop from cache, fallback to using scalac")
+              Right(
+                SimpleScalaCompilerMaker("java", Nil)
+                  .create(workspace, classesDir, buildClient, logger)
+              )
+            case _ => Left(e)
+        case e => Left(e)
+      }.fold(t => throw t, identity)
   }
 }

modules/build/src/test/scala/scala/build/tests/TestInputs.scala

@@ -86,7 +86,12 @@ final case class TestInputs(
     withCustomInputs(fromDirectory, None, skipCreatingSources) { (root, inputs) =>
       val compilerMaker = bloopConfigOpt match {
         case Some(bloopConfig) =>
-          new BloopCompilerMaker(bloopConfig, buildThreads.bloop, strictBloopJsonCheck = true)
+          new BloopCompilerMaker(
+            bloopConfig,
+            buildThreads.bloop,
+            strictBloopJsonCheck = true,
+            offline = false
+          )
         case None =>
           SimpleScalaCompilerMaker("java", Nil)
       }

modules/cli/src/main/scala/scala/cli/commands/shared/CoursierOptions.scala

@@ -3,7 +3,7 @@ package scala.cli.commands.shared
 import caseapp.*
 import com.github.plokhotnyuk.jsoniter_scala.core.*
 import com.github.plokhotnyuk.jsoniter_scala.macros.*
-import coursier.cache.{CacheLogger, FileCache}
+import coursier.cache.{CacheLogger, CachePolicy, FileCache}
 
 import scala.cli.commands.tags
 import scala.concurrent.duration.Duration
@@ -26,7 +26,12 @@ final case class CoursierOptions(
   @HelpMessage("Enable checksum validation of artifacts downloaded by coursier")
   @Tag(tags.implementation)
   @Hidden
-    coursierValidateChecksums: Option[Boolean] = None
+    coursierValidateChecksums: Option[Boolean] = None,
+
+  @Group(HelpGroup.Dependency.toString)
+  @HelpMessage("Disable using the network to download dependencies, use only the cache")
+  @Tag(tags.experimental)
+    offline: Option[Boolean] = None
 ) {
   // format: on
 
@@ -42,6 +47,12 @@ final case class CoursierOptions(
       baseCache = baseCache.withTtl(ttl0)
     for (loc <- cache.filter(_.trim.nonEmpty))
       baseCache = baseCache.withLocation(loc)
+
+    offline.foreach {
+      case true  => baseCache = baseCache.withCachePolicies(Seq(CachePolicy.LocalOnly))
+      case false => baseCache
+    }
+
     baseCache
   }
 }

modules/cli/src/main/scala/scala/cli/commands/shared/SharedOptions.scala

@@ -401,7 +401,8 @@ final case class SharedOptions(
         verbosity = Some(logging.verbosity),
         strictBloopJsonCheck = strictBloopJsonCheck,
         interactive = Some(() => interactive),
-        exclude = exclude.map(Positioned.commandLine)
+        exclude = exclude.map(Positioned.commandLine),
+        offline = coursier.offline
       ),
       notForBloopOptions = bo.PostBuildOptions(
         scalaJsLinkerOptions = linkerOptions(js),
@@ -543,7 +544,8 @@ final case class SharedOptions(
       new BloopCompilerMaker(
         value(bloopRifleConfig()),
         threads.bloop,
-        strictBloopJsonCheckOrDefault
+        strictBloopJsonCheckOrDefault,
+        coursier.offline.getOrElse(false)
       )
     else
       SimpleScalaCompilerMaker("java", Nil)

modules/integration/src/test/scala/scala/cli/integration/RunTestDefinitions.scala

@@ -1818,4 +1818,134 @@ abstract class RunTestDefinitions(val scalaVersionOpt: Option[String])
       }
     }
   }
+
+  test("offline mode should fail on missing artifacts") {
+    // Kill bloop deamon to test scalac fallback
+    os.proc(TestUtil.cli, "--power", "bloop", "exit")
+      .call(cwd = os.pwd)
+
+    val depScalaVersion = actualScalaVersion match {
+      case sv if sv.startsWith("2.12") => "2.12"
+      case sv if sv.startsWith("2.13") => "2.13"
+      case sv if sv.startsWith("3")    => "3"
+    }
+
+    val dep = s"com.lihaoyi:os-lib_$depScalaVersion:0.9.1"
+    val inputs = TestInputs(
+      os.rel / "NoDeps.scala" ->
+        """//> using jvm zulu:11
+          |object NoDeps extends App {
+          |  println("Hello from NoDeps")
+          |}
+          |""".stripMargin,
+      os.rel / "WithDeps.scala" ->
+        s"""//> using jvm zulu:11
+           |//> using dep $dep
+           |
+           |object WithDeps extends App {
+           |  println("Hello from WithDeps")
+           |}
+           |""".stripMargin
+    )
+    inputs.fromRoot { root =>
+      val cachePath = root / ".cache"
+      os.makeDir(cachePath)
+
+      val extraEnv = Map("COURSIER_CACHE" -> cachePath.toString)
+
+      val emptyCacheWalkSize = os.walk(cachePath).size
+
+      val noArtifactsRes = os.proc(
+        TestUtil.cli,
+        "--power",
+        "NoDeps.scala",
+        extraOptions,
+        "--offline",
+        "--cache",
+        cachePath.toString
+      )
+        .call(cwd = root, check = false, mergeErrIntoOut = true)
+      expect(noArtifactsRes.exitCode == 1)
+
+      // Cache unchanged
+      expect(emptyCacheWalkSize == os.walk(cachePath).size)
+
+      // Download the artifacts for scala
+      os.proc(TestUtil.cs, "install", s"scala:$actualScalaVersion")
+        .call(cwd = root, env = extraEnv)
+      os.proc(TestUtil.cs, "install", s"scalac:$actualScalaVersion")
+        .call(cwd = root, env = extraEnv)
+
+      // Download JVM that won't suit Bloop, also no Bloop artifacts are present
+      os.proc(TestUtil.cs, "java-home", "--jvm", "zulu:11")
+        .call(cwd = root, env = extraEnv)
+
+      val scalaJvmCacheWalkSize = os.walk(cachePath).size
+
+      val scalaAndJvmRes = os.proc(
+        TestUtil.cli,
+        "--power",
+        "NoDeps.scala",
+        extraOptions,
+        "--offline",
+        "--cache",
+        cachePath.toString,
+        "-v",
+        "-v"
+      )
+        .call(cwd = root, mergeErrIntoOut = true)
+      expect(scalaAndJvmRes.exitCode == 0)
+      expect(scalaAndJvmRes.out.trim().contains(
+        "Couldn't fetch Bloop from cache, fallback to using scalac"
+      ))
+      expect(scalaAndJvmRes.out.trim().contains("Hello from NoDeps"))
+
+      // Cache unchanged
+      expect(scalaJvmCacheWalkSize == os.walk(cachePath).size)
+
+      // Missing dependencies
+      val missingDepsRes = os.proc(
+        TestUtil.cli,
+        "--power",
+        "WithDeps.scala",
+        extraOptions,
+        "--offline",
+        "--cache",
+        cachePath.toString
+      )
+        .call(cwd = root, check = false, mergeErrIntoOut = true)
+      expect(missingDepsRes.exitCode == 1)
+      expect(missingDepsRes.out.trim().contains("Error downloading com.lihaoyi:os-lib"))
+
+      // Cache unchanged
+      expect(scalaJvmCacheWalkSize == os.walk(cachePath).size)
+
+      // Download dependencies
+      os.proc(TestUtil.cs, "fetch", dep)
+        .call(cwd = root, env = extraEnv)
+
+      val withDependencyCacheWalkSize = os.walk(cachePath).size
+
+      val depsRes = os.proc(
+        TestUtil.cli,
+        "--power",
+        "WithDeps.scala",
+        extraOptions,
+        "--offline",
+        "--cache",
+        cachePath.toString,
+        "-v",
+        "-v"
+      )
+        .call(cwd = root, mergeErrIntoOut = true)
+      expect(depsRes.exitCode == 0)
+      expect(
+        depsRes.out.trim().contains("Couldn't fetch Bloop from cache, fallback to using scalac")
+      )
+      expect(depsRes.out.trim().contains("Hello from WithDeps"))
+
+      // Cache changed
+      expect(withDependencyCacheWalkSize == os.walk(cachePath).size)
+    }
+  }
 }

modules/options/src/main/scala/scala/build/options/BuildOptions.scala

@@ -1,7 +1,7 @@
 package scala.build.options
 
 import com.github.plokhotnyuk.jsoniter_scala.core.*
-import coursier.cache.{ArchiveCache, FileCache}
+import coursier.cache.{ArchiveCache, FileCache, UnArchiver}
 import coursier.core.{Repository, Version}
 import coursier.parse.RepositoryParser
 import coursier.util.{Artifact, Task}
@@ -305,6 +305,8 @@ final case class BuildOptions(
     val svOpt: Option[String] = scalaOptions.scalaVersion match {
       case Some(MaybeScalaVersion(None)) =>
         None
+      case Some(MaybeScalaVersion(Some(svInput))) if internal.offline.getOrElse(false) =>
+        Some(svInput)
       case Some(MaybeScalaVersion(Some(svInput))) =>
         val sv = value {
           svInput match {
@@ -345,16 +347,19 @@ final case class BuildOptions(
               )
           }
         }
+//        match {
+//          // A maven-metadata containing available scala versions may not be available in the cache,
+//          // so we can skip the version validation hoping that it is correct
+//          // The maven metadata is absent even after cs install scala(c):3.3.0
+//          case Left(e) if internal.offline.getOrElse(false) =>
+//            println(s"!!! Caught exception: $e")
+//            e.printStackTrace(System.out)
+//            svInput
+//          case leftOrRight => value(leftOrRight)
+//        }
         Some(sv)
 
-      case None =>
-        val allStableVersions =
-          ScalaVersionUtil.allMatchingVersions(None, finalCache, value(finalRepositories))
-            .filter(ScalaVersionUtil.isStable)
-        val sv = value {
-          ScalaVersionUtil.default(allStableVersions)
-        }
-        Some(sv)
+      case None => Some(Constants.defaultScalaVersion)
     }
 
     svOpt match {

modules/options/src/main/scala/scala/build/options/InternalOptions.scala

@@ -25,7 +25,8 @@ final case class InternalOptions(
     */
   keepResolution: Boolean = false,
   extraSourceFiles: Seq[Positioned[os.Path]] = Nil,
-  exclude: Seq[Positioned[String]] = Nil
+  exclude: Seq[Positioned[String]] = Nil,
+  offline: Option[Boolean] = None
 ) {
   def verbosityOrDefault: Int = verbosity.getOrElse(0)
   def strictBloopJsonCheckOrDefault: Boolean =

website/docs/reference/cli-options.md

@@ -213,6 +213,33 @@ Aliases: `-f`
 
 Force overwriting values for key
 
+## Coursier options
+
+Available in commands:
+
+[`bloop`](./commands.md#bloop), [`bloop exit`](./commands.md#bloop-exit), [`bloop start`](./commands.md#bloop-start), [`bsp`](./commands.md#bsp), [`compile`](./commands.md#compile), [`config`](./commands.md#config), [`dependency-update`](./commands.md#dependency-update), [`doc`](./commands.md#doc), [`export`](./commands.md#export), [`fmt` , `format` , `scalafmt`](./commands.md#fmt), [`package`](./commands.md#package), [`pgp push`](./commands.md#pgp-push), [`publish`](./commands.md#publish), [`publish local`](./commands.md#publish-local), [`publish setup`](./commands.md#publish-setup), [`repl` , `console`](./commands.md#repl), [`run`](./commands.md#run), [`github secret create` , `gh secret create`](./commands.md#github-secret-create), [`setup-ide`](./commands.md#setup-ide), [`shebang`](./commands.md#shebang), [`test`](./commands.md#test), [`uninstall`](./commands.md#uninstall)
+
+<!-- Automatically generated, DO NOT EDIT MANUALLY -->
+
+### `--ttl`
+
+[Internal]
+Specify a TTL for changing dependencies, such as snapshots
+
+### `--cache`
+
+[Internal]
+Set the coursier cache location
+
+### `--coursier-validate-checksums`
+
+[Internal]
+Enable checksum validation of artifacts downloaded by coursier
+
+### `--offline`
+
+Disable using the network to download dependencies, use only the cache
+
 ## Cross options
 
 Available in commands:
@@ -1848,29 +1875,6 @@ Aliases: `--name`
 [Internal]
 Name of BSP
 
-### Coursier options
-
-Available in commands:
-
-[`bloop`](./commands.md#bloop), [`bloop exit`](./commands.md#bloop-exit), [`bloop start`](./commands.md#bloop-start), [`bsp`](./commands.md#bsp), [`compile`](./commands.md#compile), [`config`](./commands.md#config), [`dependency-update`](./commands.md#dependency-update), [`doc`](./commands.md#doc), [`export`](./commands.md#export), [`fmt` , `format` , `scalafmt`](./commands.md#fmt), [`package`](./commands.md#package), [`pgp push`](./commands.md#pgp-push), [`publish`](./commands.md#publish), [`publish local`](./commands.md#publish-local), [`publish setup`](./commands.md#publish-setup), [`repl` , `console`](./commands.md#repl), [`run`](./commands.md#run), [`github secret create` , `gh secret create`](./commands.md#github-secret-create), [`setup-ide`](./commands.md#setup-ide), [`shebang`](./commands.md#shebang), [`test`](./commands.md#test), [`uninstall`](./commands.md#uninstall)
-
-<!-- Automatically generated, DO NOT EDIT MANUALLY -->
-
-### `--ttl`
-
-[Internal]
-Specify a TTL for changing dependencies, such as snapshots
-
-### `--cache`
-
-[Internal]
-Set the coursier cache location
-
-### `--coursier-validate-checksums`
-
-[Internal]
-Enable checksum validation of artifacts downloaded by coursier
-
 ### Default file options
 
 Available in commands: