Use ENSO_JAVA=espresso to turn on Espresso support

CHANGELOG.md

@@ -923,6 +923,7 @@
 - [Warning.get_all returns only unique warnings][6372]
 - [Reimplement `enso_project` as a proper builtin][6352]
 - [Limit number of reported warnings per value][6577]
+- [Experimental support for Espresso Java interpreter][6966]
 - [Suggestions are updated only when the type of the expression changes][6755]
 - [Add project creation time to project metadata][6780]
 - [Upgrade GraalVM to 22.3.1 JDK17][6750]
@@ -1064,6 +1065,7 @@
 [6372]: https://github.com/enso-org/enso/pull/6372
 [6352]: https://github.com/enso-org/enso/pull/6352
 [6577]: https://github.com/enso-org/enso/pull/6577
+[6966]: https://github.com/enso-org/enso/pull/6966
 [6750]: https://github.com/enso-org/enso/pull/6750
 [6755]: https://github.com/enso-org/enso/pull/6755
 [6780]: https://github.com/enso-org/enso/pull/6780

docs/infrastructure/native-image.md

@@ -201,9 +201,7 @@ safely.
 ### Engine runner Configuration
 
 The Native Image generation for the Engine Runner is currently in a preview
-state. Limitations are currently mostly due to
-[Java interop](https://www.pivotaltracker.com/story/show/183260380) and loading
-of stdlib components. To generate the Native Image for runner simply execute
+state. To generate the Native Image for runner simply execute
 
 ```
 sbt> engine-runner/buildNativeImage
@@ -217,4 +215,27 @@ and execute the binary on a sample factorial test program
 
 The task that generates the Native Image, along with all the necessary
 configuration, reside in a separate project due to a bug in the currently used
-GraalVM version.
+GraalVM version. As September 2023 it can execute all Enso code, but cannot invoke `IO.println`
+or other library functions that require [polyglot java import](../../docs/polyglot/java.md),
+but read on...
+
+### Engine with Espresso
+
+Since [PR-6966](https://github.com/enso-org/enso/pull/6966) there is an experimental
+support for including [Espresso Java interpreter](https://www.graalvm.org/jdk17/reference-manual/java-on-truffle/)
+to allow use of some library functions (like `IO.println`) in the _Native Image_ built
+runner.
+
+The support can be enabled by setting environment variable `ENSO_JAVA=espresso` and
+making sure Espresso is installed in GraalVM executing the Enso engine - e.g. by
+running `graalvm/bin/gu install espresso`. Then execute:
+
+```bash
+$ cat >hello.enso
+import Standard.Base.IO
+
+main = IO.println <| "Hello World!"
+$ ENSO_JAVA=espresso ./enso-x.y.z-dev/bin/enso --run hello.enso
+```
+Unless you see a warning containing _"No language for id java found."_ your code
+has just successfully been executed by [Espresso](https://www.graalvm.org/jdk17/reference-manual/java-on-truffle/)!

engine/runtime/src/main/java/org/enso/interpreter/runtime/EnsoContext.java

@@ -1,17 +1,5 @@
 package org.enso.interpreter.runtime;
 
-import com.oracle.truffle.api.CompilerDirectives.CompilationFinal;
-import com.oracle.truffle.api.CompilerDirectives.TruffleBoundary;
-import com.oracle.truffle.api.TruffleFile;
-import com.oracle.truffle.api.TruffleLanguage;
-import com.oracle.truffle.api.TruffleLanguage.Env;
-import com.oracle.truffle.api.TruffleLogger;
-import com.oracle.truffle.api.interop.InteropLibrary;
-import com.oracle.truffle.api.interop.UnknownIdentifierException;
-import com.oracle.truffle.api.interop.UnsupportedMessageException;
-import com.oracle.truffle.api.nodes.Node;
-import com.oracle.truffle.api.object.Shape;
-import com.oracle.truffle.api.source.Source;
 import java.io.BufferedReader;
 import java.io.File;
 import java.io.InputStream;
@@ -26,7 +14,7 @@
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.atomic.AtomicLong;
 import java.util.logging.Level;
-import java.util.stream.StreamSupport;
+
 import org.enso.compiler.Compiler;
 import org.enso.compiler.PackageRepository;
 import org.enso.compiler.PackageRepositoryUtils;
@@ -66,6 +54,7 @@
 import com.oracle.truffle.api.interop.UnsupportedMessageException;
 import com.oracle.truffle.api.nodes.Node;
 import com.oracle.truffle.api.object.Shape;
+import com.oracle.truffle.api.source.Source;
 
 import scala.jdk.javaapi.OptionConverters;
 
@@ -405,14 +394,6 @@ public Optional<Module> findModuleByExpressionId(UUID expressionId) {
    */
   @TruffleBoundary
   public Object lookupJavaClass(String className) {
-    var isHosted = "hosted".equals(System.getenv("ENSO_JAVA"));
-    Object java;
-    if (!isHosted) {
-      var src = Source.newBuilder("java", "<Bindings>", "getbindings.java").build();
-      java = environment.parsePublic(src).call();
-    } else {
-      java = null;
-    }
     List<String> items = Arrays.asList(className.split("\\."));
     for (int i = items.size() - 1; i >= 0; i--) {
       String pkgName = String.join(".", items.subList(0, i));
@@ -421,10 +402,10 @@ public Object lookupJavaClass(String className) {
           i < items.size() - 1 ? items.subList(i + 1, items.size()) : List.of();
       try {
         Object hostSymbol;
-        if (isHosted) {
+        if (findGuestJava() == null) {
           hostSymbol = environment.lookupHostSymbol(pkgName + "." + curClassName);
         } else {
-          hostSymbol = InteropLibrary.getUncached().readMember(java, pkgName + "." + curClassName);
+          hostSymbol = InteropLibrary.getUncached().readMember(findGuestJava(), pkgName + "." + curClassName);
         }
         if (nestedClassPart.isEmpty()) {
           return hostSymbol;
@@ -438,6 +419,34 @@ public Object lookupJavaClass(String className) {
     return null;
   }
 
+  private Object guestJava = this;
+
+  @TruffleBoundary
+  private Object findGuestJava() throws IllegalStateException {
+    if (guestJava != this) {
+      return guestJava;
+    }
+    guestJava = null;
+    var envJava = System.getenv("ENSO_JAVA");
+    if ("espresso".equals(envJava)) {
+      var src = Source.newBuilder("java", "<Bindings>", "getbindings.java").build();
+      try {
+        guestJava = environment.parsePublic(src).call();
+      } catch (Exception ex) {
+        if (ex.getMessage().contains("No language for id java found.")) {
+          logger.log(Level.SEVERE, "Environment variable ENSO_JAVA=" + envJava + ", but " + ex.getMessage());
+          logger.log(Level.SEVERE, "Use " + System.getProperty("java.home") + "/bin/gu install espresso");
+          logger.log(Level.SEVERE, "Continuing in regular Java mode");
+        } else {
+          var ise = new IllegalStateException(ex.getMessage());
+          ise.setStackTrace(ex.getStackTrace());
+          throw ise;
+        }
+      }
+    }
+    return guestJava;
+  }
+
   /**
    * Finds the package the provided module belongs to.
    *

engine/runtime/src/main/java/org/enso/interpreter/runtime/scope/DebugLocalScope.java

@@ -6,25 +6,22 @@
 import com.oracle.truffle.api.interop.InteropLibrary;
 import com.oracle.truffle.api.interop.UnknownIdentifierException;
 import com.oracle.truffle.api.interop.UnsupportedMessageException;
+import com.oracle.truffle.api.library.CachedLibrary;
 import com.oracle.truffle.api.library.ExportLibrary;
 import com.oracle.truffle.api.library.ExportMessage;
 import com.oracle.truffle.api.source.SourceSection;
-
 import java.util.ArrayList;
 import java.util.Comparator;
 import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;
 import java.util.stream.Collectors;
-
 import org.enso.interpreter.EnsoLanguage;
 import org.enso.interpreter.node.EnsoRootNode;
 import org.enso.interpreter.runtime.callable.function.Function;
 import org.enso.interpreter.runtime.data.EnsoObject;
 import org.enso.interpreter.runtime.error.DataflowError;
 
-import com.oracle.truffle.api.library.CachedLibrary;
-
 /**
  * This class serves as a basic support for debugging with Chrome inspector. Currently, only
  * function scopes are supported.