Construct ILuaMachines in one go

This means creating an ILuaMachine is largely atomic - it either is
created or it fails.

projects/common/src/testMod/kotlin/dan200/computercraft/gametest/core/ManagedComputers.kt

@@ -4,12 +4,10 @@
 
 package dan200.computercraft.gametest.core
 
-import dan200.computercraft.api.lua.ILuaAPI
 import dan200.computercraft.core.apis.OSAPI
 import dan200.computercraft.core.lua.CobaltLuaMachine
 import dan200.computercraft.core.lua.ILuaMachine
 import dan200.computercraft.core.lua.MachineEnvironment
-import dan200.computercraft.core.lua.MachineResult
 import dan200.computercraft.gametest.api.thenOnComputer
 import dan200.computercraft.mixin.gametest.GameTestInfoAccessor
 import dan200.computercraft.shared.computer.core.ServerContext
@@ -60,52 +58,18 @@ object ManagedComputers : ILuaMachine.Factory {
         return monitor
     }
 
-    override fun create(environment: MachineEnvironment): ILuaMachine = DelegateMachine(environment)
+    override fun create(environment: MachineEnvironment, bios: InputStream): ILuaMachine {
-
+        val os = environment.apis.asSequence().filterIsInstance(OSAPI::class.java).first()
-    private class DelegateMachine(private val environment: MachineEnvironment) : ILuaMachine {
+        val id = os.computerID
-        private val apis = mutableListOf<ILuaAPI>()
+        val label = os.computerLabel
-        private var delegate: ILuaMachine? = null
+        return when {
-
+            id != 1 -> CobaltLuaMachine(environment, bios)
-        override fun addAPI(api: ILuaAPI) {
+            label != null && label[0] != null -> KotlinMachine(environment, label[0] as String)
-            val delegate = this.delegate
+            else -> {
-            if (delegate != null) return delegate.addAPI(api)
+                LOGGER.error("Kotlin Lua machine must have a label")
-
+                CobaltLuaMachine(environment, bios)
-            apis.add(api)
-
-            if (api is OSAPI) {
-                val id = api.computerID
-                val label = api.computerLabel
-                val newMachine = when {
-                    id != 1 -> CobaltLuaMachine(environment)
-                    label != null && label[0] != null -> KotlinMachine(environment, label[0] as String)
-                    else -> {
-                        LOGGER.error("Kotlin Lua machine must have a label")
-                        CobaltLuaMachine(environment)
-                    }
-                }
-
-                this.delegate = newMachine
-                for (api in apis) newMachine.addAPI(api)
             }
         }
-
-        override fun loadBios(bios: InputStream): MachineResult {
-            val delegate = this.delegate ?: return MachineResult.error("Computer not created")
-            return delegate.loadBios(bios)
-        }
-
-        override fun handleEvent(eventName: String?, arguments: Array<out Any>?): MachineResult {
-            val delegate = this.delegate ?: return MachineResult.error("Computer not created")
-            return delegate.handleEvent(eventName, arguments)
-        }
-
-        override fun printExecutionState(out: StringBuilder) {
-            delegate?.printExecutionState(out)
-        }
-
-        override fun close() {
-            delegate?.close()
-        }
     }
 
     private class KotlinMachine(environment: MachineEnvironment, private val label: String) :

projects/core/src/main/java/dan200/computercraft/core/computer/ComputerExecutor.java

@@ -14,15 +14,16 @@ import dan200.computercraft.core.filesystem.FileSystem;
 import dan200.computercraft.core.filesystem.FileSystemException;
 import dan200.computercraft.core.lua.ILuaMachine;
 import dan200.computercraft.core.lua.MachineEnvironment;
+import dan200.computercraft.core.lua.MachineException;
 import dan200.computercraft.core.metrics.Metrics;
 import dan200.computercraft.core.metrics.MetricsObserver;
 import dan200.computercraft.core.util.Colour;
-import dan200.computercraft.core.util.IoUtil;
 import dan200.computercraft.core.util.Nullability;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import javax.annotation.Nullable;
+import java.io.IOException;
 import java.io.InputStream;
 import java.util.ArrayDeque;
 import java.util.ArrayList;
@@ -377,24 +378,20 @@ final class ComputerExecutor {
         }
 
         // Create the lua machine
-        var machine = luaFactory.create(new MachineEnvironment(
+        try (var bios = biosStream) {
-            new LuaContext(computer), metrics, timeout, computer.getGlobalEnvironment().getHostString()
+            return luaFactory.create(new MachineEnvironment(
-        ));
+                new LuaContext(computer), metrics, timeout,
-
+                () -> apis.stream().map(api -> api instanceof ApiWrapper wrapper ? wrapper.getDelegate() : api).iterator(),
-        // Add the APIs. We unwrap them (yes, this is horrible) to get access to the underlying object.
+                computer.getGlobalEnvironment().getHostString()
-        for (var api : apis) machine.addAPI(api instanceof ApiWrapper wrapper ? wrapper.getDelegate() : api);
+            ), bios);
-
+        } catch (IOException e) {
-        // Start the machine running the bios resource
+            LOG.error("Failed to read bios.lua", e);
-        var result = machine.loadBios(biosStream);
+            displayFailure("Error loading bios.lua", null);
-        IoUtil.closeQuietly(biosStream);
+            return null;
-
+        } catch (MachineException e) {
-        if (result.isError()) {
+            displayFailure("Error loading bios.lua", e.getMessage());
-            machine.close();
-            displayFailure("Error loading bios.lua", result.getMessage());
             return null;
         }
-
-        return machine;
     }
 
     private void turnOn() throws InterruptedException {

projects/core/src/main/java/dan200/computercraft/core/lua/CobaltLuaMachine.java

@@ -14,6 +14,7 @@ import dan200.computercraft.core.asm.LuaMethod;
 import dan200.computercraft.core.asm.ObjectSource;
 import dan200.computercraft.core.computer.TimeoutState;
 import dan200.computercraft.core.metrics.Metrics;
+import dan200.computercraft.core.util.Nullability;
 import dan200.computercraft.core.util.ThreadUtils;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -27,6 +28,7 @@ import org.squiddev.cobalt.lib.*;
 import org.squiddev.cobalt.lib.platform.VoidResourceManipulator;
 
 import javax.annotation.Nullable;
+import java.io.IOException;
 import java.io.InputStream;
 import java.io.Serial;
 import java.nio.ByteBuffer;
@@ -62,7 +64,7 @@ public class CobaltLuaMachine implements ILuaMachine {
     private @Nullable LuaThread mainRoutine = null;
     private @Nullable String eventFilter = null;
 
-    public CobaltLuaMachine(MachineEnvironment environment) {
+    public CobaltLuaMachine(MachineEnvironment environment, InputStream bios) throws MachineException, IOException {
         timeout = environment.timeout();
         context = environment.context();
         debug = new TimeoutDebugHandler();
@@ -115,10 +117,20 @@ public class CobaltLuaMachine implements ILuaMachine {
         if (CoreConfig.disableLua51Features) {
             globals.rawset("_CC_DISABLE_LUA51_FEATURES", Constants.TRUE);
         }
+
+        // Add default APIs
+        for (var api : environment.apis()) addAPI(api);
+
+        // And load the BIOS
+        try {
+            var value = LoadState.load(state, bios, "@bios.lua", globals);
+            mainRoutine = new LuaThread(state, value, globals);
+        } catch (CompileException e) {
+            throw new MachineException(Nullability.assertNonNull(e.getMessage()));
+        }
     }
 
-    @Override
+    private void addAPI(ILuaAPI api) {
-    public void addAPI(ILuaAPI api) {
         if (globals == null) throw new IllegalStateException("Machine has been closed");
 
         // Add the methods of an API to the global table
@@ -132,25 +144,6 @@ public class CobaltLuaMachine implements ILuaMachine {
         for (var name : names) globals.rawset(name, table);
     }
 
-    @Override
-    public MachineResult loadBios(InputStream bios) {
-        if (mainRoutine != null) throw new IllegalStateException("Already set up the machine");
-        if (state == null || globals == null) throw new IllegalStateException("Machine has been destroyed.");
-
-        try {
-            var value = LoadState.load(state, bios, "@bios.lua", globals);
-            mainRoutine = new LuaThread(state, value, globals);
-            return MachineResult.OK;
-        } catch (CompileException e) {
-            close();
-            return MachineResult.error(e);
-        } catch (Exception e) {
-            LOG.warn("Could not load bios.lua", e);
-            close();
-            return MachineResult.GENERIC_ERROR;
-        }
-    }
-
     @Override
     public MachineResult handleEvent(@Nullable String eventName, @Nullable Object[] arguments) {
         if (mainRoutine == null || state == null) throw new IllegalStateException("Machine has been closed");

projects/core/src/main/java/dan200/computercraft/core/lua/ILuaMachine.java

@@ -4,10 +4,8 @@
 
 package dan200.computercraft.core.lua;
 
-import dan200.computercraft.api.lua.IDynamicLuaObject;
-import dan200.computercraft.api.lua.ILuaAPI;
-
 import javax.annotation.Nullable;
+import java.io.IOException;
 import java.io.InputStream;
 
 /**
@@ -17,32 +15,8 @@ import java.io.InputStream;
  * There should only be one concrete implementation at any one time, which is currently {@link CobaltLuaMachine}. If
  * external mod authors are interested in registering their own machines, we can look into how we can provide some
  * mechanism for registering these.
- * <p>
- * This should provide implementations of {@link dan200.computercraft.api.lua.ILuaContext}, and the ability to convert
- * {@link IDynamicLuaObject}s into something the VM understands, as well as handling method calls.
  */
 public interface ILuaMachine {
-    /**
-     * Inject an API into the global environment of this machine. This should construct an object, as it would for any
-     * {@link IDynamicLuaObject} and set it to all names in {@link ILuaAPI#getNames()}.
-     * <p>
-     * Called before {@link #loadBios(InputStream)}.
-     *
-     * @param api The API to register.
-     */
-    void addAPI(ILuaAPI api);
-
-    /**
-     * Create a function from the provided program, and set it up to run when {@link #handleEvent(String, Object[])} is
-     * called.
-     * <p>
-     * This should destroy the machine if it failed to load the bios.
-     *
-     * @param bios The stream containing the boot program.
-     * @return The result of loading this machine. Will either be OK, or the error message when loading the bios.
-     */
-    MachineResult loadBios(InputStream bios);
-
     /**
      * Resume the machine, either starting or resuming the coroutine.
      * <p>
@@ -71,6 +45,16 @@ public interface ILuaMachine {
     void close();
 
     interface Factory {
-        ILuaMachine create(MachineEnvironment environment);
+        /**
+         * Attempt to create a Lua machine.
+         *
+         * @param environment The environment under which to create the machine.
+         * @param bios        The {@link InputStream} which contains the initial function to run. This should be used to
+         *                    load the initial function - it should <em>NOT</em> be executed.
+         * @return The successfully created machine, or an error.
+         * @throws IOException      If reading the underlying {@link InputStream} failed.
+         * @throws MachineException An error occurred while creating the machine.
+         */
+        ILuaMachine create(MachineEnvironment environment, InputStream bios) throws IOException, MachineException;
     }
 }

projects/core/src/main/java/dan200/computercraft/core/lua/MachineEnvironment.java

@@ -4,6 +4,7 @@
 
 package dan200.computercraft.core.lua;
 
+import dan200.computercraft.api.lua.ILuaAPI;
 import dan200.computercraft.api.lua.ILuaContext;
 import dan200.computercraft.core.computer.GlobalEnvironment;
 import dan200.computercraft.core.computer.TimeoutState;
@@ -17,6 +18,8 @@ import dan200.computercraft.core.metrics.MetricsObserver;
  * @param metrics    A sink to submit metrics to. You do not need to submit task timings here, it should only be for additional
  *                   metrics such as {@link Metrics#COROUTINES_CREATED}
  * @param timeout    The current timeout state. This should be used by the machine to interrupt its execution.
+ * @param apis       APIs to inject into the global environment. Each API should be converted into a Lua object
+ *                   (following the same rules as any other value), and then set to all names in {@link ILuaAPI#getNames()}.
  * @param hostString A {@linkplain GlobalEnvironment#getHostString() host string} to identify the current environment.
  * @see ILuaMachine.Factory
  */
@@ -24,6 +27,7 @@ public record MachineEnvironment(
     ILuaContext context,
     MetricsObserver metrics,
     TimeoutState timeout,
+    Iterable<ILuaAPI> apis,
     String hostString
 ) {
 }

projects/core/src/main/java/dan200/computercraft/core/lua/MachineException.java

@@ -0,0 +1,25 @@
+// SPDX-FileCopyrightText: 2023 The CC: Tweaked Developers
+//
+// SPDX-License-Identifier: MPL-2.0
+
+package dan200.computercraft.core.lua;
+
+import java.io.Serial;
+
+/**
+ * An exception thrown by a {@link ILuaMachine}.
+ */
+public class MachineException extends Exception {
+    @Serial
+    private static final long serialVersionUID = 400833668352232261L;
+
+    /**
+     * Create a new {@link MachineException}.
+     *
+     * @param message The message to display. This should be user-friendly, and not contain any internal information -
+     *                that should just be logged to the console.
+     */
+    public MachineException(String message) {
+        super(message);
+    }
+}

projects/core/src/main/java/dan200/computercraft/core/lua/MachineResult.java

@@ -7,14 +7,12 @@ package dan200.computercraft.core.lua;
 import dan200.computercraft.core.computer.TimeoutState;
 
 import javax.annotation.Nullable;
-import java.io.InputStream;
 
 /**
  * The result of executing an action on a machine.
  * <p>
  * Errors should halt the machine and display the error to the user.
  *
- * @see ILuaMachine#loadBios(InputStream)
  * @see ILuaMachine#handleEvent(String, Object[])
  */
 public final class MachineResult {

projects/core/src/test/java/dan200/computercraft/core/ComputerTestDelegate.java

@@ -17,7 +17,7 @@ import dan200.computercraft.core.filesystem.FileSystemException;
 import dan200.computercraft.core.filesystem.WritableFileMount;
 import dan200.computercraft.core.lua.CobaltLuaMachine;
 import dan200.computercraft.core.lua.MachineEnvironment;
-import dan200.computercraft.core.lua.MachineResult;
+import dan200.computercraft.core.lua.MachineException;
 import dan200.computercraft.core.terminal.Terminal;
 import dan200.computercraft.test.core.computer.BasicEnvironment;
 import it.unimi.dsi.fastutil.ints.Int2IntArrayMap;
@@ -477,14 +477,8 @@ public class ComputerTestDelegate {
      * This is a super nasty hack, but is also an order of magnitude faster than tracking this in Lua.
      */
     private class CoverageLuaMachine extends CobaltLuaMachine {
-        CoverageLuaMachine(MachineEnvironment environment) {
+        CoverageLuaMachine(MachineEnvironment environment, InputStream bios) throws MachineException, IOException {
-            super(environment);
+            super(environment, bios);
-        }
-
-        @Override
-        public MachineResult loadBios(InputStream bios) {
-            var result = super.loadBios(bios);
-            if (result != MachineResult.OK) return result;
 
             LuaTable globals;
             LuaThread mainRoutine;
@@ -535,8 +529,6 @@ public class ComputerTestDelegate {
                 }
             });
             mainRoutine.getDebugState().setHook(hook, false, true, false, 0);
-
-            return MachineResult.OK;
         }
     }
 }

projects/core/src/testFixtures/kotlin/dan200/computercraft/test/core/computer/KotlinComputerManager.kt

@@ -31,7 +31,7 @@ class KotlinComputerManager : AutoCloseable {
         BasicEnvironment(),
         ComputerThread(1),
         NoWorkMainThreadScheduler(),
-    ) { DummyLuaMachine(it) }
+    ) { env, _ -> DummyLuaMachine(env) }
     private val errorLock: Lock = ReentrantLock()
     private val hasError = errorLock.newCondition()
 
@@ -153,15 +153,11 @@ class KotlinComputerManager : AutoCloseable {
     }
 
     private inner class DummyLuaMachine(private val environment: MachineEnvironment) : KotlinLuaMachine(environment) {
-        private var tasks: Queue<FakeComputerTask>? = null
+        private val tasks: Queue<FakeComputerTask> =
-        override fun addAPI(api: ILuaAPI) {
+            environment.apis.asSequence().filterIsInstance(QueuePassingAPI::class.java).first().tasks
-            super.addAPI(api)
-            if (api is QueuePassingAPI) tasks = api.tasks
-        }
 
         override fun getTask(): (suspend KotlinLuaMachine.() -> Unit)? {
             try {
-                val tasks = this.tasks ?: throw NullPointerException("Not received tasks yet")
                 val task = tasks.remove()
                 return {
                     try {

projects/core/src/testFixtures/kotlin/dan200/computercraft/test/core/computer/KotlinLuaMachine.kt

@@ -4,13 +4,11 @@
 
 package dan200.computercraft.test.core.computer
 
-import dan200.computercraft.api.lua.ILuaAPI
 import dan200.computercraft.api.lua.ILuaContext
 import dan200.computercraft.core.lua.ILuaMachine
 import dan200.computercraft.core.lua.MachineEnvironment
 import dan200.computercraft.core.lua.MachineResult
 import kotlinx.coroutines.*
-import java.io.InputStream
 import kotlin.coroutines.CoroutineContext
 
 /**
@@ -19,9 +17,9 @@ import kotlin.coroutines.CoroutineContext
 abstract class KotlinLuaMachine(environment: MachineEnvironment) : ILuaMachine, AbstractLuaTaskContext() {
     override val context: ILuaContext = environment.context
 
-    override fun addAPI(api: ILuaAPI) = addApi(api)
+    init {
-
+        for (api in environment.apis) addApi(api)
-    override fun loadBios(bios: InputStream): MachineResult = MachineResult.OK
+    }
 
     override fun handleEvent(eventName: String?, arguments: Array<out Any>?): MachineResult {
         if (hasEventListeners) {