fix: Handle exceptions when reporting warnings in Scala 3 compiler pl…

…ugin (#3872)

* Handle exceptions when reporting warnings in ScalaNativePlugin when using incomplete Context

* Disable fatal warning when testing deprecated plugin settings

nscplugin/src/main/scala-3/scala/scalanative/nscplugin/ScalaNativePlugin.scala

@@ -2,7 +2,7 @@ package scala.scalanative.nscplugin
 
 import dotty.tools.dotc.plugins._
 import dotty.tools.dotc.report
-import dotty.tools.dotc.core.Contexts.NoContext
+import dotty.tools.dotc.core.Contexts.ContextBase
 import java.net.URI
 import java.net.URISyntaxException
 import dotty.tools.dotc.core.Contexts.Context
@@ -45,7 +45,7 @@ class ScalaNativePlugin extends StandardPlugin:
               .filter(_.isAbsolute())).distinct.sortBy(-_.getNameCount())
           )
         case (config, s"mapSourceURI:${mapping}") =>
-          given Context = NoContext
+          given Context = ContextBase().initialCtx
           report.warning("'mapSourceURI' is deprecated, it's ignored.")
           config
         case (config, _) => config

project/Build.scala

@@ -642,6 +642,9 @@ object Build {
       .enablePlugins(MyScalaNativePlugin)
       .settings(noPublishSettings)
       .settings(
+        // Setting only used to ensure that compiler does not crash when reporting deprecated options
+        scalacOptions += "-P:scalanative:mapSourceURI:path->unused",
+        scalacOptions -= "-Xfatal-warnings",
         nativeConfig ~= {
           _.withLinkStubs(true)
         },