tests: Move toolArgsFor out of PatmatExhaustivityTest

Author: dwijnand

compiler/src/dotty/tools/dotc/CompilationUnit.scala

@@ -122,7 +122,7 @@ object CompilationUnit {
         NoSource
       }
       else if (!source.file.exists) {
-        report.error(s"not found: ${source.file.path}")
+        report.error(s"source file not found: ${source.file.path}")
         NoSource
       }
       else source

compiler/test/dotty/tools/dotc/transform/PatmatExhaustivityTest.scala

@@ -10,9 +10,8 @@ import reporting.TestReporter
 import dotty.tools.io.Directory
 
 import java.io._
-import java.nio.file.{Files, Path => JPath}
+import java.nio.file.{Path => JPath}
 
-import scala.io.Source._
 import org.junit.Test
 
 class PatmatExhaustivityTest {
@@ -79,22 +78,4 @@ class PatmatExhaustivityTest {
 
     println(msg)
   }
-
-  // inspect given files for tool args of the form `tool: args`
-  // if args string ends in close comment, drop the `*` `/`
-  // if split, parse the args string as command line.
-  // (from scala.tools.partest.nest.Runner#toolArgsFor)
-  private def toolArgsFor(files: List[JPath]): List[String] = {
-    import scala.jdk.OptionConverters._
-    import config.CommandLineParser.tokenize
-    files.flatMap { path =>
-      val tag  = "scalac:"
-      val endc = "*" + "/"    // be forgiving of /* scalac: ... */
-      def stripped(s: String) = s.substring(s.indexOf(tag) + tag.length).stripSuffix(endc)
-      val args = scala.util.Using.resource(Files.lines(path, scala.io.Codec.UTF8.charSet))(
-        _.limit(10).filter(_.contains(tag)).map(stripped).findAny.toScala
-      )
-      args.map(tokenize).getOrElse(Nil)
-    }
-  }
 }

compiler/test/dotty/tools/utils.scala

@@ -3,8 +3,9 @@ package tools
 
 import java.io.File
 import java.nio.charset.StandardCharsets.UTF_8
+import java.nio.file.{Files, Path => JPath}
 
-import scala.io.Source
+import scala.io.{Codec, Source}
 import scala.reflect.ClassTag
 import scala.util.Using.resource
 import scala.util.chaining.given
@@ -25,11 +26,10 @@ extension (f: File) def absPath =
 extension (str: String) def dropExtension =
   str.reverse.dropWhile(_ != '.').drop(1).reverse
 
-private def withFile[T](file: File)(action: Source => T): T =
-  resource(Source.fromFile(file, UTF_8.name))(action)
-
-def readLines(f: File): List[String] = withFile(f)(_.getLines.toList)
-def readFile(f: File): String = withFile(f)(_.mkString)
+private
+def withFile[T](file: File)(action: Source => T)(using Codec): T      = resource(Source.fromFile(file))(action)
+def readLines(f: File)(using codec: Codec = Codec.UTF8): List[String] = withFile(f)(_.getLines.toList)
+def readFile(f: File)(using codec: Codec = Codec.UTF8): String        = withFile(f)(_.mkString)
 
 private object Unthrown extends ControlThrowable
 
@@ -43,3 +43,24 @@ def assertThrows[T <: Throwable: ClassTag](p: T => Boolean)(body: => Any): Unit
     case failed: T       => throw AssertionError(s"Exception failed check: $failed").tap(_.addSuppressed(failed))
     case NonFatal(other) => throw AssertionError(s"Wrong exception: expected ${implicitly[ClassTag[T]]} but was ${other.getClass.getName}").tap(_.addSuppressed(other))
 end assertThrows
+
+def toolArgsFor(files: List[JPath])(using codec: Codec = Codec.UTF8): List[String] =
+  files.flatMap(path => toolArgsParse(readLines(path.toFile)))
+
+// Inspect the first 10 of the given lines for compiler options of the form
+// `// scalac: args`, `/* scalac: args`, ` * scalac: args`.
+// If args string ends in close comment, drop the `*` `/`.
+// If split, parse the args string as a command line.
+// (from scala.tools.partest.nest.Runner#toolArgsFor)
+def toolArgsParse(lines: List[String]): List[String] = {
+  val tag  = "scalac:"
+  val endc = "*" + "/"    // be forgiving of /* scalac: ... */
+  def stripped(s: String) = s.substring(s.indexOf(tag) + tag.length).stripSuffix(endc)
+  val args = lines.to(LazyList).take(10).filter { s =>
+       s.contains("// " + tag)
+    || s.contains("/* " + tag)
+    || s.contains(" * " + tag)
+    // but avoid picking up comments like "% scalac ./a.scala" and "$ scalac a.scala"
+  }.map(stripped).headOption
+  args.map(dotc.config.CommandLineParser.tokenize).getOrElse(Nil)
+}