Update dottyLatestNightlyBuild to use major version from dotty.epfl.ch

Author: allanrenucci

project/Build.scala

@@ -858,7 +858,7 @@ object Build {
 
 
       sbtPlugin := true,
-      version := "0.1.6",
+      version := "0.1.7",
       ScriptedPlugin.scriptedSettings,
       ScriptedPlugin.sbtTestDirectory := baseDirectory.value / "sbt-test",
       ScriptedPlugin.scriptedLaunchOpts += "-Dplugin.version=" + version.value,

sbt-dotty/src/dotty/tools/sbtplugin/DottyPlugin.scala

@@ -13,17 +13,39 @@ object DottyPlugin extends AutoPlugin {
     // - if this was a taskKey, then you couldn't do `scalaVersion := dottyLatestNightlyBuild`
     // - if this was a settingKey, then this would evaluate even if you don't use it.
     def dottyLatestNightlyBuild: Option[String] = {
-      println("Fetching latest Dotty nightly version (requires an internet connection)...")
-      val Version = """      <version>(0.5\..*-bin.*)</version>""".r
-      val latest = scala.io.Source
-          .fromURL(
-            "http://repo1.maven.org/maven2/ch/epfl/lamp/dotty_0.5/maven-metadata.xml")
-          .getLines()
-          .collect { case Version(version) => version }
-          .toSeq
-          .lastOption
-      println(s"Latest Dotty nightly build version: $latest")
-      latest
+      println("Fetching latest Dotty nightly version...")
+
+      val nightly = try {
+        // get majorVersion from dotty.epfl.ch/versions
+        val in = new java.net.URL("http://dotty.epfl.ch/versions").openStream()
+        val versions = new java.util.Properties()
+        versions.load(in)
+        in.close()
+        val baseVersion = versions.getProperty("baseVersion")
+        val majorVersion = baseVersion.take(baseVersion.lastIndexOf('.'))
+
+        // get latest nightly version from maven
+        val Version = s"      <version>($majorVersion\\..*-bin.*)</version>".r
+        scala.io.Source
+            .fromURL(
+              s"http://repo1.maven.org/maven2/ch/epfl/lamp/dotty_$majorVersion/maven-metadata.xml")
+            .getLines()
+            .collect { case Version(version) => version }
+            .toSeq
+            .lastOption
+      } catch {
+        case _: java.io.IOException =>
+          None
+      }
+
+      nightly match {
+        case Some(version) =>
+          println(s"Latest Dotty nightly build version: $version")
+        case None =>
+          println(s"Unable to get Dotty latest nightly build version. Make sure you are connected to internet")
+      }
+
+      nightly
     }
 
     implicit class DottyCompatModuleID(moduleID: ModuleID) {