Support eval

README.md

@@ -14,7 +14,6 @@ For Maven dependency resolution, the kernel is using [ShrinkWrap resolvers](http
 
 *   [Try online](#try-online)
 *   [Features](#features)
-    *   [TODO](#todo)
 *   [Requirements](#requirements)
 *   [Installing](#installing)
 *   [Configuring](#configuring)
@@ -45,14 +44,11 @@ Currently the kernel supports
     ![maven-pom-dep](docs/img/maven-pom-dep.png)
 *   Display rich output (See also [display.md](docs/display.md) and [maven magic](docs/magics.md#addmavendependencies)). Chart library in the demo photo is [XChart](https://github.com/knowm/XChart) with the sample code taken from their README.
     ![display-img](docs/img/display-img.png)
+*   `eval` function. **Note: the signature is `Object eval(String) throws Exception`.** This evaluates the expression (a cell) in the user scope and returns the actual evaluation result instead of a serialized one.
+    ![eval](docs/img/eval.png)
 *   Configurable evaluation timeout
     ![timeout](docs/img/timeout.png)
 
-#### TODO
-
-- [ ] Support magics for making queries about the current environment.
-- [ ] Compile javadocs when displaying introspection requests as html.
-
 ### Requirements
 
 1.  [Java JDK >=9](http://www.oracle.com/technetwork/java/javase/downloads/index.html). **Not the JRE**

src/main/java/io/github/spencerpark/ijava/IJava.java

@@ -48,6 +48,7 @@ public class IJava {
     public static final String DEFAULT_SHELL_INIT_RESOURCE_PATH = "ijava-jshell-init.jshell";
     public static final String MAGICS_INIT_RESOURCE_PATH = "ijava-magics-init.jshell";
     public static final String DISPLAY_INIT_RESOURCE_PATH = "ijava-display-init.jshell";
+    public static final String EVAL_INIT_RESOURCE_PATH = "ijava-eval-init.jshell";
 
     public static final String VERSION;
 

src/main/java/io/github/spencerpark/ijava/JavaKernel.java

@@ -75,6 +75,7 @@ public JavaKernel() {
                 .startupScript(IJava.resource(IJava.DEFAULT_SHELL_INIT_RESOURCE_PATH))
                 .startupScript(IJava.resource(IJava.MAGICS_INIT_RESOURCE_PATH))
                 .startupScript(IJava.resource(IJava.DISPLAY_INIT_RESOURCE_PATH))
+                .startupScript(IJava.resource(IJava.EVAL_INIT_RESOURCE_PATH))
                 .startupScriptFiles(System.getenv(IJava.STARTUP_SCRIPTS_KEY))
                 .startupScript(System.getenv(IJava.STARTUP_SCRIPT_KEY))
                 .timeoutFromString(System.getenv(IJava.TIMEOUT_DURATION_KEY))
@@ -244,11 +245,15 @@ private List<String> formatEvaluationTimeoutException(EvaluationTimeoutException
         return fmt;
     }
 
-    @Override
-    public DisplayData eval(String expr) throws Exception {
+    public Object evalRaw(String expr) throws Exception {
         expr = this.magicsTransformer.transformMagics(expr);
 
-        Object result = this.evaluator.eval(expr);
+        return this.evaluator.eval(expr);
+    }
+
+    @Override
+    public DisplayData eval(String expr) throws Exception {
+        Object result = this.evalRaw(expr);
 
         if (result != null)
             return result instanceof DisplayData

src/main/java/io/github/spencerpark/ijava/execution/IJavaExecutionControl.java

@@ -32,6 +32,7 @@
 import java.util.Objects;
 import java.util.UUID;
 import java.util.concurrent.*;
+import java.util.concurrent.atomic.AtomicInteger;
 
 /**
  * An ExecutionControl very similar to {@link jdk.jshell.execution.LocalExecutionControl} but which
@@ -46,13 +47,13 @@ public class IJavaExecutionControl extends DirectExecutionControl {
 
     private static final Object NULL = new Object();
 
+    private static final AtomicInteger EXECUTOR_THREAD_ID = new AtomicInteger(0);
+
     private final ExecutorService executor;
 
     private final long timeoutTime;
     private final TimeUnit timeoutUnit;
 
-    private volatile Future<Object> runningTask;
-
     private final Map<String, Object> results = new ConcurrentHashMap<>();
 
     public IJavaExecutionControl() {
@@ -62,7 +63,7 @@ public IJavaExecutionControl() {
     public IJavaExecutionControl(long timeoutTime, TimeUnit timeoutUnit) {
         this.timeoutTime = timeoutTime;
         this.timeoutUnit = timeoutTime > 0 ? Objects.requireNonNull(timeoutUnit) : TimeUnit.MILLISECONDS;
-        this.executor = Executors.newSingleThreadExecutor((r) -> new Thread(r, "IJava-executor"));
+        this.executor = Executors.newCachedThreadPool(r -> new Thread(r, "IJava-executor-" + EXECUTOR_THREAD_ID.getAndIncrement()));
     }
 
     public long getTimeoutDuration() {
@@ -81,12 +82,12 @@ public Object takeResult(String key) {
     }
 
     private Object execute(Method doitMethod) throws TimeoutException, Exception {
-        this.runningTask = this.executor.submit(() -> doitMethod.invoke(null));
+        Future<Object> runningTask = this.executor.submit(() -> doitMethod.invoke(null));
 
         try {
             if (this.timeoutTime > 0)
-                return this.runningTask.get(this.timeoutTime, this.timeoutUnit);
-            return this.runningTask.get();
+                return runningTask.get(this.timeoutTime, this.timeoutUnit);
+            return runningTask.get();
         } catch (CancellationException e) {
             // If canceled this means that stop() was invoked in which case the protocol is to
             // throw an ExecutionControl.StoppedException.
@@ -132,8 +133,7 @@ protected String invoke(Method doitMethod) throws Exception {
 
     @Override
     public void stop() throws EngineTerminationException, InternalException {
-        if (this.runningTask != null)
-            this.runningTask.cancel(true);
+        this.executor.shutdownNow();
     }
 
     @Override

src/main/java/io/github/spencerpark/ijava/execution/IncompleteSourceException.java

@@ -27,6 +27,7 @@ public class IncompleteSourceException extends Exception {
     private final String source;
 
     public IncompleteSourceException(String source) {
+        super(source);
         this.source = source;
     }
 

src/main/resources/ijava-eval-init.jshell

@@ -0,0 +1,9 @@
+Object eval(String expr) throws Exception {
+    io.github.spencerpark.ijava.JavaKernel kernel = io.github.spencerpark.ijava.IJava.getKernelInstance();
+
+    if (kernel != null) {
+        return kernel.evalRaw(expr);
+    } else {
+        throw new RuntimeException("No IJava kernel running");
+    }
+}