Allow catching of exceptions in chained runnables

The user can handle exceptions of a specified type occurring in a chained
runnable by calling `executeCatching` and optionally passing a handler
function.

This is needed needed in order to gracefully stop the execution of a
runnable chain without the exception being caught by Bukkit and
resulting in it being logged as uncaught, while also allowing further
handling of the exception.

gradlew

@@ -82,6 +82,7 @@ esac
 
 CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
 
+
 # Determine the Java command to use to start the JVM.
 if [ -n "$JAVA_HOME" ] ; then
     if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
@@ -129,6 +130,7 @@ fi
 if [ "$cygwin" = "true" -o "$msys" = "true" ] ; then
     APP_HOME=`cygpath --path --mixed "$APP_HOME"`
     CLASSPATH=`cygpath --path --mixed "$CLASSPATH"`
+    
     JAVACMD=`cygpath --unix "$JAVACMD"`
 
     # We build the pattern for arguments to be converted via cygpath

gradlew.bat

@@ -29,6 +29,9 @@ if "%DIRNAME%" == "" set DIRNAME=.
 set APP_BASE_NAME=%~n0
 set APP_HOME=%DIRNAME%
 
+@rem Resolve any "." and ".." in APP_HOME to make it shorter.
+for %%i in ("%APP_HOME%") do set APP_HOME=%%~fi
+
 @rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
 set DEFAULT_JVM_OPTS="-Xmx64m" "-Xms64m"
 
@@ -81,6 +84,7 @@ set CMD_LINE_ARGS=%*
 
 set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar
 
+
 @rem Execute Gradle
 "%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %CMD_LINE_ARGS%
 

src/main/kotlin/net/axay/kspigot/runnables/ChainableRunnables.kt

@@ -4,6 +4,7 @@ package net.axay.kspigot.runnables
 
 import net.axay.kspigot.main.KSpigotMainInstance
 import org.bukkit.Bukkit
+import kotlin.reflect.KClass
 
 abstract class ChainedRunnablePart<T, R>(
     val sync: Boolean
@@ -12,20 +13,44 @@ abstract class ChainedRunnablePart<T, R>(
     var next: ChainedRunnablePart<R, *>? = null
 
     abstract fun execute()
-    
+
+    abstract fun <E : Exception> executeCatching(clazz: KClass<E>, handler: (E) -> Unit = {})
+
     protected abstract fun invoke(data: T): R
 
     protected fun start(data: T) {
-        val realRunnable = Runnable {
+        run {
             val result = invoke(data)
             next?.start(result)
         }
+    }
+
+    protected fun <E : Exception> startCatching(
+        data: T,
+        clazz: KClass<E>,
+        exceptionHandler: (E) -> Unit = {}
+    ) {
+        run {
+            try {
+                val result = invoke(data)
+                next?.startCatching(result, clazz, exceptionHandler)
+            } catch (e: Exception) {
+                if (clazz.isInstance(e)) {
+                    @Suppress("UNCHECKED_CAST")
+                    exceptionHandler(e as E)
+                } else {
+                    throw e
+                }
+            }
+        }
+    }
+
+    private fun run(realRunnable: () -> Unit) {
         if (sync)
             Bukkit.getScheduler().runTask(KSpigotMainInstance, realRunnable)
         else
             Bukkit.getScheduler().runTaskAsynchronously(KSpigotMainInstance, realRunnable)
     }
-
 }
 
 class ChainedRunnablePartFirst<R>(
@@ -35,6 +60,9 @@ class ChainedRunnablePartFirst<R>(
 
     override fun execute() = start(Unit)
 
+    override fun <E : Exception> executeCatching(clazz: KClass<E>, handler: (E) -> Unit) =
+        startCatching(Unit, clazz, handler)
+
     override fun invoke(data: Unit) = runnable.invoke()
 
 }
@@ -47,6 +75,9 @@ class ChainedRunnablePartThen<T, R>(
 
     override fun execute() = previous.execute()
 
+    override fun <E : Exception> executeCatching(clazz: KClass<E>, handler: (E) -> Unit) =
+        previous.executeCatching(clazz, handler)
+
     override fun invoke(data: T) = runnable.invoke(data)
 
 }
@@ -57,7 +88,7 @@ fun <R> firstSync(runnable: () -> R) = firstDo(true, runnable)
 fun <R> firstAsync(runnable: () -> R) = firstDo(false, runnable)
 
 // THEN
-fun <T, R, U> ChainedRunnablePart<T, R>.thenDo(sync: Boolean, runnable: (R) -> U)
-    = ChainedRunnablePartThen(runnable, sync, this).apply { previous.next = this }
+fun <T, R, U> ChainedRunnablePart<T, R>.thenDo(sync: Boolean, runnable: (R) -> U) =
+    ChainedRunnablePartThen(runnable, sync, this).apply { previous.next = this }
 fun <T, R, U> ChainedRunnablePart<T, R>.thenSync(runnable: (R) -> U) = thenDo(true, runnable)
 fun <T, R, U> ChainedRunnablePart<T, R>.thenAsync(runnable: (R) -> U) = thenDo(false, runnable)