Update Scala to version 3

pom.xml

@@ -1,16 +1,16 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
 	<modelVersion>4.0.0</modelVersion>
 
 	<parent>
 		<groupId>org.scijava</groupId>
 		<artifactId>pom-scijava</artifactId>
-		<version>27.0.1</version>
+		<version>34.0.0</version>
 		<relativePath />
 	</parent>
 
 	<artifactId>scripting-scala</artifactId>
-	<version>0.2.3-SNAPSHOT</version>
+	<version>0.3.0-SNAPSHOT</version>
 
 	<name>SciJava Scripting: Scala</name>
 	<description>JSR-223-compliant Scala scripting language plugin.</description>
@@ -53,6 +53,10 @@
 			<name>Keith Schulze</name>
 			<properties><id>keithschulze</id></properties>
 		</contributor>
+		<contributor>
+			<name>Jarek Sacha</name>
+			<properties><id>jpsacha</id></properties>
+		</contributor>
 	</contributors>
 
 	<mailingLists>
@@ -82,6 +86,7 @@
 
 	<properties>
 		<package-name>org.scijava.plugins.scripting.scala</package-name>
+		<main-class>org.scijava.plugins.scripting.scala.Main</main-class>
 
 		<license.licenseName>bsd_2</license.licenseName>
 		<license.copyrightOwners>Board of Regents of the University of
@@ -91,22 +96,62 @@ Wisconsin-Madison.</license.copyrightOwners>
 		<!-- NB: Deploy releases to the SciJava Maven repository. -->
 		<releaseProfiles>sign,deploy-to-scijava</releaseProfiles>
 
-		<scala.version>2.12.1</scala.version>
+		<scala.version>3.2.2</scala.version>
 	</properties>
 
-	<dependencies>
-		<!-- SciJava dependencies -->
-		<dependency>
-			<groupId>org.scijava</groupId>
-			<artifactId>scijava-common</artifactId>
-		</dependency>
 
-		<!-- Scala dependencies -->
-		<dependency>
-			<groupId>org.scala-lang</groupId>
-			<artifactId>scala-compiler</artifactId>
-			<version>${scala.version}</version>
-		</dependency>
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>net.alchim31.maven</groupId>
+                <artifactId>scala-maven-plugin</artifactId>
+                <version>4.8.0</version>
+				<configuration>
+					<args>
+						<arg>-unchecked</arg>
+						<arg>-deprecation</arg>
+						<arg>-explain</arg>
+						<arg>-explain-types</arg>
+						<arg>-release</arg>
+						<arg>8</arg>
+					</args>
+				</configuration>
+				<executions>
+					<execution>
+						<id>scala-compile-first</id>
+						<phase>process-resources</phase>
+						<goals>
+							<goal>add-source</goal>
+							<goal>compile</goal>
+						</goals>
+					</execution>
+					<execution>
+						<id>scala-test-compile</id>
+						<phase>process-test-resources</phase>
+						<goals>
+							<goal>testCompile</goal>
+						</goals>
+					</execution>
+				</executions>
+            </plugin>
+        </plugins>
+    </build>
+
+    <dependencies>
+        <!-- SciJava dependencies -->
+        <dependency>
+            <groupId>org.scijava</groupId>
+            <artifactId>scijava-common</artifactId>
+        </dependency>
+
+        <!-- Scala dependencies -->
+        <dependency>
+            <groupId>org.scala-lang</groupId>
+            <artifactId>scala3-compiler_3</artifactId>
+            <version>${scala.version}</version>
+            <exclusions>
+            </exclusions>
+        </dependency>
 
 		<!-- Test dependencies -->
 		<dependency>

src/main/java/org/scijava/plugins/scripting/scala/ScalaScriptEngine.java → src/main/java/org/scijava/plugins/scripting/scala/Main.java

@@ -1,19 +1,18 @@
-/*
+/*-
  * #%L
  * JSR-223-compliant Scala scripting language plugin.
  * %%
- * Copyright (C) 2013 - 2016 Board of Regents of the University of
- * Wisconsin-Madison.
+ * Copyright (C) 2014 - 2023 SciJava developers.
  * %%
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
- *
+ * 
  * 1. Redistributions of source code must retain the above copyright notice,
  *    this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright notice,
  *    this list of conditions and the following disclaimer in the documentation
  *    and/or other materials provided with the distribution.
- *
+ * 
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
@@ -27,45 +26,13 @@
  * POSSIBILITY OF SUCH DAMAGE.
  * #L%
  */
-
 package org.scijava.plugins.scripting.scala;
 
-import javax.script.ScriptEngine;
-import javax.script.ScriptException;
-
-import org.scijava.script.AdaptedScriptEngine;
-
-/**
- * Scala interpreter
- *
- * @author Keith Schulze
- * @see ScriptEngine
- */
-public class ScalaScriptEngine extends AdaptedScriptEngine {
-
-    public ScalaScriptEngine(ScriptEngine engine) {
-        super(engine);
-    }
-
-    @Override
-    public Object get(String key) {
-        // First try to get value from bindings
-        Object value = super.get(key);
+import org.scijava.script.ScriptREPL;
 
-        // NB: Extracting values from Scala Script Engine are a little tricky.
-        // Values (variables) initialised or computed in the script are
-        // not added to the bindings of the CompiledScript AFAICT. Therefore
-        // the only way to extract them is to evaluate the variable and
-        // capture the return. If it evaluates to null or throws a
-        // a ScriptException, we simply return null.
-        if (value == null) try {
-            value = super.eval(key);
-        } catch (ScriptException ignored) {
-            // HACK: Explicitly ignore ScriptException, which arises if
-            // key is not found. This feels bad because it fails silently
-            // for the user, but it mimics behaviour in other script langs.
-        }
+public class Main {
 
-        return value;
-    }
+	public static void main(String... args) throws Exception {
+		ScriptREPL.main(args);
+	}
 }

src/main/java/org/scijava/plugins/scripting/scala/ScalaScriptLanguage.java

@@ -30,10 +30,6 @@
 
 package org.scijava.plugins.scripting.scala;
 
-import java.net.URLClassLoader;
-import java.util.Arrays;
-import java.util.stream.Collectors;
-
 import javax.script.ScriptEngine;
 
 import org.scijava.log.LogService;
@@ -42,17 +38,13 @@
 import org.scijava.script.AdaptedScriptLanguage;
 import org.scijava.script.ScriptLanguage;
 
-import scala.tools.nsc.ConsoleWriter;
-import scala.tools.nsc.NewLinePrintWriter;
-import scala.tools.nsc.Settings;
-import scala.tools.nsc.interpreter.Scripted;
-
 /**
  * An adapter of the Scala interpreter to the SciJava scripting interface.
  * 
  * @author Curtis Rueden
  * @author Keith Schulze
  * @author Johannes Schindelin
+ * @author Jarek Sacha
  * @see ScriptEngine
  */
 @Plugin(type = ScriptLanguage.class, name = "Scala")
@@ -67,25 +59,7 @@ public ScalaScriptLanguage() {
 
 	@Override
 	public ScriptEngine getScriptEngine() {
-		final Settings settings = new Settings();
-		settings.classpath().value_$eq(getClasspath());
-
-		Scripted eng = Scripted.apply(new Scripted.Factory(), settings,
-				new NewLinePrintWriter(new ConsoleWriter(), true));
-
-		return new ScalaScriptEngine(eng);
-	}
-
-	/** Retrieves the current classpath as a string. */
-	private String getClasspath() {
-		final ClassLoader cl = ClassLoader.getSystemClassLoader();
-		if (!(cl instanceof URLClassLoader)) {
-			log.warn("Cannot retrieve classpath from class loader of type '" +
-				cl.getClass().getName() + "'");
-			return System.getProperty("java.class.path");
-		}
-		return Arrays.stream(((URLClassLoader) cl).getURLs()).map(//
-			url -> url.getPath() //
-		).collect(Collectors.joining(System.getProperty("path.separator")));
+		final ScriptEngine eng = new dotty.tools.repl.ScriptEngine();
+		return new ScalaAdaptedScriptEngine(eng);
 	}
 }

src/main/scala/org/scijava/plugins/scripting/scala/ScalaAdaptedScriptEngine.scala

@@ -0,0 +1,135 @@
+package org.scijava.plugins.scripting.scala
+
+import java.io.{OutputStream, Reader, StringWriter, Writer}
+import javax.script.*
+import scala.collection.mutable
+import scala.jdk.CollectionConverters.*
+import scala.util.Try
+
+/**
+ * Adapted Scala ScriptEngine
+ *
+ * @author Jarek Sacha
+ * @author Keith Schulze
+ * @see ScriptEngine
+ */
+class ScalaAdaptedScriptEngine(engine: ScriptEngine) extends AbstractScriptEngine:
+
+  import ScalaAdaptedScriptEngine.*
+
+  private val buffer = new Array[Char](8192)
+
+  @throws[ScriptException]
+  override def eval(reader: Reader, context: ScriptContext): AnyRef = eval(stringFromReader(reader), context)
+
+  @throws[ScriptException]
+  override def eval(script: String, context: ScriptContext): AnyRef =
+    emulateBinding(context)
+    val r = evalInner(script, context)
+    // Scala returns `Unit` when no value is returned. Script Engine (or the
+    // Java side) expects `null` when no value was returned.
+    // Anything else return as is.
+    r match
+      case _: Unit => null
+      case x       => x
+
+  private def emulateBinding(context: ScriptContext): Unit =
+
+    // Scala 3.2.2 ignores bindings, emulate binding using setup script
+    // Create a line with variable declaration for each binding item
+    val lines =
+      for
+        scope    <- context.getScopes.asScala
+        bindings <- Option(context.getBindings(scope)).map(_.asScala) // bindings in context can be null
+      yield {
+        for (name, value) <- bindings yield {
+          value match
+            case v: Double  => s"val $name : Double = ${v}d"
+            case v: Float   => s"val $name : Float = ${v}f"
+            case v: Long    => s"val $name : Long = ${v}L"
+            case v: Int     => s"val $name : Int = $v"
+            case v: Char    => s"val $name : Char = '$v'"
+            case v: Short   => s"val $name : Short = $v"
+            case v: Byte    => s"val $name : Byte = $v"
+            case v: Boolean => s"val $name : Int = $v"
+            case o: AnyRef if isValidVariableName(name) =>
+              _transfer = o
+              val typeName = Option(o).map(_.getClass.getCanonicalName).getOrElse("AnyRef")
+              s"""
+                 |val $name : $typeName = {
+                 |  val t = org.scijava.plugins.scripting.scala.ScalaAdaptedScriptEngine._transfer
+                 |  t.asInstanceOf[$typeName]
+                 |}""".stripMargin
+            case _: AnyRef => "" // ignore if name is not a variable
+            case v: Unit =>
+              throw ScriptException(s"Unsupported type for bind variable $name: ${v.getClass}")
+        }
+      }
+
+    val script = lines
+      .flatten
+      .filter(_.nonEmpty)
+      .mkString("\n")
+
+    if script.nonEmpty then
+      evalInner(script, context)
+
+  end emulateBinding
+
+  private def evalInner(script: String, context: ScriptContext) =
+    class WriterOutputStream(w: Writer) extends OutputStream:
+      override def write(b: Int): Unit = w.write(b)
+
+    // Redirect output to writes provided by context
+    Console.withOut(WriterOutputStream(context.getWriter)) {
+      Console.withErr(WriterOutputStream(context.getErrorWriter)) {
+        engine.eval(script, context)
+      }
+    }
+
+  private def stringFromReader(in: Reader) =
+    val out = new StringWriter()
+    var n   = in.read(buffer)
+    while n > -1 do
+      out.write(buffer, 0, n)
+      n = in.read(buffer)
+    in.close()
+    out.toString
+
+  override def createBindings(): Bindings = engine.createBindings
+
+  override def getFactory: ScriptEngineFactory = engine.getFactory
+
+  override def get(key: String): AnyRef =
+    // First try to get value from bindings
+    var value = super.get(key)
+
+    // NB: Extracting values from Scala Script Engine are a little tricky.
+    // Values (variables) initialised or computed in the script are
+    // not added to the bindings of the CompiledScript AFAICT. Therefore
+    // the only way to extract them is to evaluate the variable and
+    // capture the return. If it evaluates to null or throws a
+    // a ScriptException, we simply return null.
+    if value == null then
+      try
+        value = evalInner(key, getContext)
+      catch
+        case _: ScriptException =>
+        // HACK: Explicitly ignore ScriptException, which arises if
+        // key is not found. This feels bad because it fails silently
+        // for the user, but it mimics behaviour in other script langs.
+
+    value
+  end get
+
+end ScalaAdaptedScriptEngine
+
+object ScalaAdaptedScriptEngine:
+  private lazy val variableNamePattern = """^[a-zA-Z_$][a-zA-Z_$0-9]*$""".r
+
+  /** Do not use externally despite it is declared public. IT is public so it is accessible from scripts */
+  // noinspection ScalaWeakerAccess
+  var _transfer: Object = _
+
+  private def isValidVariableName(name: String): Boolean = variableNamePattern.matches(name)
+end ScalaAdaptedScriptEngine