Merge branch 'master' into 1.17

src/main/java/carpet/CarpetSettings.java

@@ -417,20 +417,26 @@ public class CarpetSettings
 
     private static class ModulePermissionLevel extends Validator<String> {
         @Override public String validate(ServerCommandSource source, ParsedRule<String> currentRule, String newValue, String string) {
-            CarpetSettings.runPermissionLevel = SettingsManager.getCommandLevel(newValue);
+            int permissionLevel = SettingsManager.getCommandLevel(newValue);
+            if (source != null && !source.hasPermissionLevel(permissionLevel))
+                return null;
+            CarpetSettings.runPermissionLevel = permissionLevel;
+            CarpetServer.settingsManager.notifyPlayersCommandsChanged();
             return newValue;
         }
         @Override
-        public String description() { return "Also controls permission level of commands executed via `run()`";}
+        public String description() { return "When changing the rule, you must at least have the permission level you are trying to give it";}
     }
     @Rule(
             desc = "Enables restrictions for arbitrary code execution with scarpet",
             extra = {
                     "Users that don't have this permission level",
-                    "won't be able to load apps or /script run"
+                    "won't be able to load apps or /script run.",
+                    "It is also the permission level apps will",
+                    "have when running commands with run()"
             },
-            category = {COMMAND, SCARPET},
-            validate = ModulePermissionLevel.class
+            category = {SCARPET},
+            validate = {Validator._COMMAND_LEVEL_VALIDATOR.class, ModulePermissionLevel.class}
     )
     public static String commandScriptACE = "ops";
 

src/main/java/carpet/script/CarpetScriptServer.java

@@ -26,6 +26,7 @@ import net.minecraft.util.WorldSavePath;
 import net.minecraft.util.math.BlockPos;
 
 import java.io.IOException;
+import java.nio.file.FileVisitOption;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.ArrayList;
@@ -136,7 +137,8 @@ public class CarpetScriptServer
     {
         try {
             Path folder = server.getSavePath(WorldSavePath.ROOT).resolve("scripts");
-            Files.createDirectories(folder);
+            if (!Files.exists(folder)) 
+                Files.createDirectories(folder);
             Optional<Path>
             scriptPath = Files.list(folder)
                 .filter(script -> 
@@ -149,7 +151,8 @@ public class CarpetScriptServer
             if (FabricLoader.getInstance().getEnvironmentType() == EnvType.CLIENT)
             {
                 Path globalFolder = FabricLoader.getInstance().getConfigDir().resolve("carpet/scripts");
-                Files.createDirectories(globalFolder);
+                if (!Files.exists(globalFolder)) 
+                    Files.createDirectories(globalFolder);
                 scriptPath = Files.walk(globalFolder)
                         .filter(script -> script.getFileName().toString().equalsIgnoreCase(name + ".sc") ||
                                 (allowLibraries && script.getFileName().toString().equalsIgnoreCase(name + ".scl")))
@@ -194,7 +197,8 @@ public class CarpetScriptServer
         }
         try {
             Path worldScripts = server.getSavePath(WorldSavePath.ROOT).resolve("scripts");
-            Files.createDirectories(worldScripts);
+            if (!Files.exists(worldScripts)) 
+                Files.createDirectories(worldScripts);
             Files.list(worldScripts)
                 .filter(f -> f.toString().endsWith(".sc"))
                 .forEach(f -> moduleNames.add(f.getFileName().toString().replaceFirst("\\.sc$","").toLowerCase(Locale.ROOT)));
@@ -202,8 +206,9 @@ public class CarpetScriptServer
             if (includeBuiltIns && (FabricLoader.getInstance().getEnvironmentType() == EnvType.CLIENT))
             {
                 Path globalScripts = FabricLoader.getInstance().getConfigDir().resolve("carpet/scripts");
-                Files.createDirectories(globalScripts);
-                Files.walk(globalScripts)
+                if (!Files.exists(globalScripts))
+                    Files.createDirectories(globalScripts);
+                Files.walk(globalScripts, FileVisitOption.FOLLOW_LINKS)
                     .filter(f -> f.toString().endsWith(".sc"))
                     .forEach(f -> moduleNames.add(f.getFileName().toString().replaceFirst("\\.sc$","").toLowerCase(Locale.ROOT)));
             }

src/main/java/carpet/script/Expression.java

@@ -19,7 +19,6 @@ import carpet.script.exception.ExpressionException;
 import carpet.script.exception.InternalExpressionException;
 import carpet.script.exception.ResolvedException;
 import carpet.script.exception.ReturnStatement;
-import carpet.script.exception.ThrowStatement;
 import carpet.script.language.Arithmetic;
 import carpet.script.language.ControlFlow;
 import carpet.script.language.DataStructures;
@@ -232,7 +231,7 @@ public class Expression
         if (exc instanceof ExitStatement)
             return exc;
         if (exc instanceof InternalExpressionException)
-            return new ExpressionException(c, e, token, exc.getMessage(), ((InternalExpressionException) exc).stack);
+            return ((InternalExpressionException) exc).promote(c, e, token);
         if (exc instanceof ArithmeticException)
             return new ExpressionException(c, e, token, "Your math is wrong, "+exc.getMessage());
         if (exc instanceof ResolvedException)
@@ -624,9 +623,9 @@ public class Expression
         {
             return exprProvider.get().evalValue(c, expectedType);
         }
-        catch (ContinueStatement | BreakStatement | ReturnStatement | ThrowStatement exc)
+        catch (ContinueStatement | BreakStatement | ReturnStatement exc)
         {
-            throw new ExpressionException(c, this, "Control flow functions, like continue, break, throw or return, should only be used in loops, try blocks, and functions respectively.");
+            throw new ExpressionException(c, this, "Control flow functions, like continue, break or return, should only be used in loops, and functions respectively.");
         }
         catch (ExitStatement exit)
         {

src/main/java/carpet/script/Tokenizer.java

@@ -406,6 +406,7 @@ public class Tokenizer implements Iterator<Tokenizer.Token>
         public int pos;
         public int linepos;
         public int lineno;
+        public static final Token NONE = new Token();
         public Token morphedInto(TokenType newType, String newSurface)
         {
             Token created = new Token();

src/main/java/carpet/script/api/Auxiliary.java

@@ -19,6 +19,8 @@ import carpet.script.argument.FunctionArgument;
 import carpet.script.argument.Vector3Argument;
 import carpet.script.exception.ExitStatement;
 import carpet.script.exception.InternalExpressionException;
+import carpet.script.exception.ThrowStatement;
+import carpet.script.exception.Throwables;
 import carpet.script.utils.FixedCommandSource;
 import carpet.script.utils.InputValidator;
 import carpet.script.utils.ScarpetJsonDeserializer;
@@ -79,6 +81,7 @@ import net.minecraft.text.LiteralText;
 import net.minecraft.text.Text;
 import net.minecraft.util.Identifier;
 import net.minecraft.util.InvalidIdentifierException;
+import net.minecraft.util.crash.CrashException;
 import net.minecraft.util.Util;
 import net.minecraft.util.WorldSavePath;
 import net.minecraft.util.dynamic.RegistryOps;
@@ -166,10 +169,11 @@ public class Auxiliary {
     {
         expression.addLazyFunction("sound", -1, (c, t, lv) -> {
             CarpetContext cc = (CarpetContext)c;
-            Identifier soundName = new Identifier(lv.get(0).evalValue(c).getString());
+            String rawString = lv.get(0).evalValue(c).getString();
+            Identifier soundName = new Identifier(rawString);
             Vector3Argument locator = Vector3Argument.findIn(cc, lv, 1);
             if (Registry.SOUND_EVENT.get(soundName) == null)
-                throw new InternalExpressionException("No such sound: "+soundName.getPath());
+                throw new ThrowStatement(rawString, Throwables.UNKNOWN_SOUND);
             float volume = 1.0F;
             float pitch = 1.0F;
             SoundCategory mixer = SoundCategory.MASTER;
@@ -876,7 +880,15 @@ public class Auxiliary {
             Value retVal;
             if (fdesc.getMiddle().equals("nbt"))
             {
-                Tag state = ((CarpetScriptHost) c.host).readFileTag(fdesc.getLeft(), fdesc.getRight());
+                Tag state;
+                try
+                {
+                    state = ((CarpetScriptHost) c.host).readFileTag(fdesc.getLeft(), fdesc.getRight());
+                } catch (CrashException e)
+                {
+                    throw new ThrowStatement((fdesc.getRight()?"shared/":"")+ fdesc.getLeft(), Throwables.NBT_READ);
+                }
+
                 if (state == null) return LazyValue.NULL;
                 retVal = new NBTSerializableValue(state);
             }
@@ -889,10 +901,13 @@ public class Auxiliary {
                 }
                 catch (JsonParseException e)
                 {
-                    Throwable exception = e;
+                    Throwable exc = e;
                     if(e.getCause() != null)
-                        exception = e.getCause();
-                    throw new InternalExpressionException("Failed to read JSON file: "+exception.getMessage());
+                        exc = e.getCause();
+                    throw new ThrowStatement(MapValue.wrap(ImmutableMap.of(
+                            StringValue.of("error"), StringValue.of(exc.getMessage()),
+                            StringValue.of("path"), StringValue.of((fdesc.getRight()?"shared/":"")+ fdesc.getLeft())
+                    )), Throwables.JSON_READ);
                 }
                 Value parsedJson = GSON.fromJson(json, Value.class);
                 if (parsedJson == null)
@@ -980,7 +995,14 @@ public class Auxiliary {
                     shared = lv.get(1).evalValue(c).getBoolean();
                 }
             }
-            Tag state = ((CarpetScriptHost)((CarpetContext)c).host).readFileTag(file, shared);
+            Tag state;
+            try
+            {
+                state = ((CarpetScriptHost)((CarpetContext)c).host).readFileTag(file, shared);
+            } catch (CrashException e)
+            {
+                throw new ThrowStatement("app data", Throwables.NBT_READ);
+            }
             if (state == null)
                 return (cc, tt) -> Value.NULL;
             Value retVal = new NBTSerializableValue(state);

src/main/java/carpet/script/api/Inventories.java

@@ -6,6 +6,8 @@ import carpet.script.CarpetContext;
 import carpet.script.Expression;
 import carpet.script.LazyValue;
 import carpet.script.exception.InternalExpressionException;
+import carpet.script.exception.ThrowStatement;
+import carpet.script.exception.Throwables;
 import carpet.script.value.ListValue;
 import carpet.script.value.NBTSerializableValue;
 import carpet.script.value.NullValue;
@@ -119,14 +121,7 @@ public class Inventories {
                 }
             }
             List<Recipe<?>> recipes;
-            try
-            {
-                recipes = ((RecipeManagerInterface) cc.s.getMinecraftServer().getRecipeManager()).getAllMatching(type, new Identifier(recipeName));
-            }
-            catch (InvalidIdentifierException ignored)
-            {
-                return LazyValue.NULL;
-            }
+            recipes = ((RecipeManagerInterface) cc.s.getMinecraftServer().getRecipeManager()).getAllMatching(type, new Identifier(recipeName));
             if (recipes.isEmpty())
                 return LazyValue.NULL;
             List<Value> recipesOutput = new ArrayList<>();
@@ -197,17 +192,9 @@ public class Inventories {
         {
             String itemStr = lv.get(0).evalValue(c).getString();
             Item item;
-            try
-            {
-                Identifier id = new Identifier(itemStr);
-                item = Registry.ITEM.get(id);
-                if (item == Items.AIR && !id.getPath().equalsIgnoreCase("air"))
-                    throw new InvalidIdentifierException("boo");
-            }
-            catch (InvalidIdentifierException ignored)
-            {
-                throw new InternalExpressionException("Incorrect item: "+itemStr);
-            }
+            Identifier id = new Identifier(itemStr);
+            item = Registry.ITEM.getOrEmpty(id).orElseThrow(() -> new ThrowStatement(itemStr, Throwables.UNKNOWN_ITEM));
+
             if (!item.hasRecipeRemainder()) return LazyValue.NULL;
             Value ret = new StringValue(NBTSerializableValue.nameFromRegistryId(Registry.ITEM.getId(item.getRecipeRemainder())));
             return (_c, _t ) -> ret;

src/main/java/carpet/script/api/Scoreboards.java

@@ -6,6 +6,8 @@ import carpet.script.CarpetContext;
 import carpet.script.Expression;
 import carpet.script.LazyValue;
 import carpet.script.exception.InternalExpressionException;
+import carpet.script.exception.ThrowStatement;
+import carpet.script.exception.Throwables;
 import carpet.script.value.EntityValue;
 import carpet.script.value.ListValue;
 import carpet.script.value.NullValue;
@@ -131,7 +133,7 @@ public class Scoreboards {
                 criterion = ScoreboardCriterion.getOrCreateStatCriterion(critetionName).orElse(null);
                 if (criterion==null)
                 {
-                    throw new InternalExpressionException("Unknown scoreboard criterion: "+critetionName);
+                    throw new ThrowStatement(critetionName, Throwables.UNKNOWN_CRITERION);
                 }
             }
 

src/main/java/carpet/script/api/WorldAccess.java

@@ -19,6 +19,8 @@ import carpet.script.LazyValue;
 import carpet.script.argument.BlockArgument;
 import carpet.script.argument.Vector3Argument;
 import carpet.script.exception.InternalExpressionException;
+import carpet.script.exception.ThrowStatement;
+import carpet.script.exception.Throwables;
 import carpet.script.utils.BiomeInfo;
 import carpet.script.utils.WorldTools;
 import carpet.script.value.BlockValue;
@@ -59,7 +61,6 @@ import net.minecraft.item.SwordItem;
 import net.minecraft.item.TridentItem;
 import net.minecraft.nbt.CompoundTag;
 import net.minecraft.nbt.Tag;
-import net.minecraft.server.MinecraftServer;
 import net.minecraft.server.network.ServerPlayerEntity;
 import net.minecraft.server.world.ChunkTicket;
 import net.minecraft.server.world.ChunkTicketType;
@@ -106,7 +107,6 @@ import java.util.Locale;
 import java.util.Map;
 import java.util.Optional;
 import java.util.function.BiFunction;
-import java.util.function.Function;
 import java.util.function.Predicate;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
@@ -336,8 +336,8 @@ public class WorldAccess {
                 String poiType = lv.get(locator.offset+1).evalValue(c).getString().toLowerCase(Locale.ROOT);
                 if (!"any".equals(poiType))
                 {
-                    PointOfInterestType type =  Registry.POINT_OF_INTEREST_TYPE.get(new Identifier(poiType));
-                    if (type == PointOfInterestType.UNEMPLOYED && !"unemployed".equals(poiType)) return LazyValue.NULL;
+                    PointOfInterestType type =  Registry.POINT_OF_INTEREST_TYPE.getOrEmpty(new Identifier(poiType))
+                            .orElseThrow(() -> new ThrowStatement(poiType, Throwables.UNKNOWN_POI));
                     condition = (tt) -> tt == type;
                 }
                 if (locator.offset + 2 < lv.size())
@@ -391,9 +391,8 @@ public class WorldAccess {
                 return LazyValue.FALSE;
             }
             String poiTypeString = poi.getString().toLowerCase(Locale.ROOT);
-            PointOfInterestType type =  Registry.POINT_OF_INTEREST_TYPE.get(new Identifier(poiTypeString));
-            // solving lack of null with defaulted registries
-            if (type == PointOfInterestType.UNEMPLOYED && !"unemployed".equals(poiTypeString)) throw new InternalExpressionException("Unknown POI type: "+poiTypeString);
+            PointOfInterestType type =  Registry.POINT_OF_INTEREST_TYPE.getOrEmpty(new Identifier(poiTypeString))
+            		.orElseThrow(() -> new ThrowStatement(poiTypeString, Throwables.UNKNOWN_POI));
             int occupancy = 0;
             if (locator.offset + 1 < lv.size())
             {
@@ -872,9 +871,8 @@ public class WorldAccess {
                 {
                     playerBreak = true;
                     String itemString = val.getString();
-                    item = Registry.ITEM.get(new Identifier(itemString));
-                    if (item == Items.AIR && !itemString.equals("air"))
-                        throw new InternalExpressionException("Incorrect item: " + itemString);
+                    item = Registry.ITEM.getOrEmpty(new Identifier(itemString))
+                            .orElseThrow(() -> new ThrowStatement(itemString, Throwables.UNKNOWN_ITEM));
                 }
             }
             CompoundTag tag = null;
@@ -1152,7 +1150,7 @@ public class WorldAccess {
             if (locator.replacement != null)
             {
                 biome = world.getRegistryManager().get(Registry.BIOME_KEY).get(new Identifier(locator.replacement));
-                if (biome == null) return LazyValue.NULL;
+                if (biome == null) throw new ThrowStatement(locator.replacement, Throwables.UNKNOWN_BIOME) ;
             }
             else
             {
@@ -1181,9 +1179,8 @@ public class WorldAccess {
                 throw new InternalExpressionException("'set_biome' needs a biome name as an argument");
             String biomeName = lv.get(locator.offset+0).evalValue(c).getString();
             // from locatebiome command code
-            Biome biome = cc.s.getMinecraftServer().getRegistryManager().get(Registry.BIOME_KEY).get(new Identifier(biomeName));
-            if (biome == null)
-                throw new InternalExpressionException("Unknown biome: "+biomeName);
+            Biome biome = cc.s.getMinecraftServer().getRegistryManager().get(Registry.BIOME_KEY).getOrEmpty(new Identifier(biomeName))
+                .orElseThrow(() -> new ThrowStatement(biomeName, Throwables.UNKNOWN_BIOME));
             boolean doImmediateUpdate = true;
             if (lv.size() > locator.offset+1)
             {
@@ -1252,8 +1249,8 @@ public class WorldAccess {
                 if (!(requested instanceof NullValue))
                 {
                     String reqString = requested.getString();
-                    structure = Registry.STRUCTURE_FEATURE.get(new Identifier(reqString));
-                    if (structure == null) throw new InternalExpressionException("Unknown structure: " + reqString);
+                    structure = Registry.STRUCTURE_FEATURE.getOrEmpty(new Identifier(reqString))
+                            .orElseThrow(() -> new ThrowStatement(reqString, Throwables.UNKNOWN_STRUCTURE));
                 }
                 if (lv.size() > locator.offset+1)
                 {
@@ -1333,7 +1330,7 @@ public class WorldAccess {
                 throw new InternalExpressionException("'set_structure requires at least position and a structure name");
             String structureName = lv.get(locator.offset).evalValue(c).getString().toLowerCase(Locale.ROOT);
             ConfiguredStructureFeature<?, ?> configuredStructure = FeatureGenerator.resolveConfiguredStructure(structureName, world, pos);
-            if (configuredStructure == null) throw new InternalExpressionException("Unknown structure: "+structureName);
+            if (configuredStructure == null) throw new ThrowStatement(structureName, Throwables.UNKNOWN_STRUCTURE);
             // good 'ol pointer
             Value[] result = new Value[]{Value.NULL};
             // technically a world modification. Even if we could let it slide, we will still park it

src/main/java/carpet/script/exception/ExpressionException.java

@@ -8,28 +8,44 @@ import carpet.script.value.FunctionValue;
 
 import java.util.ArrayList;
 import java.util.List;
+import java.util.function.Supplier;
 
 /* The expression evaluators exception class. */
 public class ExpressionException extends RuntimeException implements ResolvedException
 {
     public final Context context;
+    public final Tokenizer.Token token;
     public final List<FunctionValue> stack = new ArrayList<>();
+    private final Supplier<String> lazyMessage;
+    private String cachedMessage = null;
 
     public ExpressionException(Context c, Expression e, String message)
     {
-        super(makeMessage(c, e, null, message));
-        context = c;
+        this(c, e, Tokenizer.Token.NONE, message);
     }
 
     public ExpressionException(Context c, Expression e, Tokenizer.Token t, String message)
     {
-        super(makeMessage(c, e, t, message));
+        super("Error");
+        lazyMessage = () -> makeMessage(c, e, t, message);
+        token = t;
         context = c;
     }
     public ExpressionException(Context c, Expression e, Tokenizer.Token t, String message, List<FunctionValue> stack)
     {
-        super(makeMessage(c, e, t, message));
+        super("Error");
         this.stack.addAll(stack);
+        lazyMessage = () -> makeMessage(c, e, t, message);
+        token = t;
+        context = c;
+    }
+
+    public ExpressionException(Context c, Expression e, Tokenizer.Token t, Supplier<String> messageSupplier, List<FunctionValue> stack)
+    {
+        super("Error");
+        this.stack.addAll(stack);
+        lazyMessage = () -> makeMessage(c, e, t, messageSupplier.get());
+        token = t;
         context = c;
     }
 
@@ -68,4 +84,13 @@ public class ExpressionException extends RuntimeException implements ResolvedExc
         }
         return String.join("\n", errorMaker.apply(e, t, message));
     }
+    
+    @Override
+    public String getMessage() {
+        if (cachedMessage == null)
+        {
+        	cachedMessage = lazyMessage.get();
+        }
+        return cachedMessage;
+    }
 }

src/main/java/carpet/script/exception/InternalExpressionException.java

@@ -1,5 +1,8 @@
 package carpet.script.exception;
 
+import carpet.script.Context;
+import carpet.script.Expression;
+import carpet.script.Tokenizer;
 import carpet.script.value.FunctionValue;
 
 import java.util.ArrayList;
@@ -13,4 +16,20 @@ public class InternalExpressionException extends RuntimeException
     {
         super(message);
     }
+    
+    /**
+     * <p>Promotes this simple exception into one with context and extra information.
+     * 
+     * <p>Provides a cleaner way of handling similar exceptions, in this case
+     * {@link InternalExpressionException} and {@link ThrowStatement} 
+     * @param c Context
+     * @param e Expression
+     * @param token Token
+     * @return The new {@link ExpressionException} (or {@link ProcessedThrowStatement}),
+     *         depending on the implementation.
+     */
+    public ExpressionException promote(Context c, Expression e, Tokenizer.Token token)
+    {
+        return new ExpressionException(c, e, token, getMessage(), stack);
+    }
 }

src/main/java/carpet/script/exception/ProcessedThrowStatement.java

@@ -0,0 +1,20 @@
+package carpet.script.exception;
+
+import java.util.List;
+
+import carpet.script.Context;
+import carpet.script.Expression;
+import carpet.script.Tokenizer.Token;
+import carpet.script.value.FunctionValue;
+import carpet.script.value.Value;
+
+public class ProcessedThrowStatement extends ExpressionException {
+    public final Throwables thrownExceptionType;
+    public final Value data;
+    
+    public ProcessedThrowStatement(Context c, Expression e, Token token, List<FunctionValue> stack, Throwables thrownExceptionType, Value data) {
+        super(c, e, token, ()  -> "Unhandled "+thrownExceptionType.getId()+" exception: "+data.getString(), stack);
+        this.thrownExceptionType = thrownExceptionType;
+        this.data = data;
+    }
+}

src/main/java/carpet/script/exception/ThrowStatement.java

@@ -1,11 +1,54 @@
 package carpet.script.exception;
 
+import carpet.script.Context;
+import carpet.script.Expression;
+import carpet.script.Tokenizer.Token;
+import carpet.script.value.StringValue;
 import carpet.script.value.Value;
 
-public class ThrowStatement extends ExitStatement
+public class ThrowStatement extends InternalExpressionException
 {
-    public ThrowStatement(Value value)
+    private final Throwables type;
+    private final Value data;
+    
+    /**
+     * Creates a throw exception from a value, and assigns it a specified message.
+     * <p>To be used when throwing from Scarpet's {@code throw} function
+     * @param data The value to pass
+     * @param type Exception type
+     */
+    public ThrowStatement(Value data, Throwables type)
     {
-        super(value);
+        super(type.getId());
+        this.data = data;
+        this.type = type;
+    }
+
+    public ThrowStatement(Value data, Throwables parent, String subtype)
+    {
+        super(subtype);
+        this.data = data;
+        this.type = new Throwables(subtype, parent);
+    }
+
+    /**
+     * Creates a throw exception.<br>
+     * Conveniently creates a value from the {@code value} String
+     * to be used easily in Java code
+     * @param message The message to display when not handled
+     * @param type An {@link Throwables} containing the inheritance data
+     *                  for this exception. When throwing from Java,
+     *                  those exceptions should be pre-registered.
+     */
+    public ThrowStatement(String message, Throwables type)
+    {
+        super(type.getId());
+        this.data = StringValue.of(message);
+        this.type = type;
+    }
+    
+    @Override
+    public ExpressionException promote(Context c, Expression e, Token token) {
+        return new ProcessedThrowStatement(c, e, token, stack, type, data);
     }
 }

src/main/java/carpet/script/exception/Throwables.java

@@ -0,0 +1,89 @@
+package carpet.script.exception;
+
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * This class contains default Scarpet catchable types, as well as their inheritance and
+ * methods to check whether filters are compatible with those.
+ */
+public class Throwables {
+    private final String id;
+    private final Throwables parent;
+
+    private static final Map<String, Throwables> byId = new HashMap<>();
+
+    public static final Throwables THROWN_EXCEPTION_TYPE = register("exception", null);
+    public static final Throwables VALUE_EXCEPTION       = register("value_exception", THROWN_EXCEPTION_TYPE);
+    public static final Throwables UNKNOWN_ITEM          = register("unknown_item", VALUE_EXCEPTION);
+    public static final Throwables UNKNOWN_BLOCK         = register("unknown_block", VALUE_EXCEPTION);
+    public static final Throwables UNKNOWN_BIOME         = register("unknown_biome", VALUE_EXCEPTION);
+    public static final Throwables UNKNOWN_SOUND         = register("unknown_sound", VALUE_EXCEPTION);
+    public static final Throwables UNKNOWN_PARTICLE      = register("unknown_particle", VALUE_EXCEPTION);
+    public static final Throwables UNKNOWN_POI           = register("unknown_poi", VALUE_EXCEPTION);
+    public static final Throwables UNKNOWN_DIMENSION     = register("unknown_dimension", VALUE_EXCEPTION);
+    public static final Throwables UNKNOWN_STRUCTURE     = register("unknown_structure", VALUE_EXCEPTION);
+    public static final Throwables UNKNOWN_CRITERION     = register("unknown_criterion", VALUE_EXCEPTION);
+    public static final Throwables IO_EXCEPTION          = register("io_exception", THROWN_EXCEPTION_TYPE);
+    public static final Throwables NBT_READ              = register("nbt_read_error", IO_EXCEPTION);
+    public static final Throwables JSON_READ             = register("json_read_error", IO_EXCEPTION);
+    public static final Throwables USER_DEFINED          = register("user_exception", THROWN_EXCEPTION_TYPE);
+
+    /**
+     * Creates an exception and registers it to be used as parent for
+     * user defined exceptions in Scarpet's throw function.
+     * <p>Scarpet exceptions should have a top-level parent being {@link Throwables#THROWN_EXCEPTION_TYPE}
+     * @param id The value for the exception as a {@link String}.
+     * @param parent The parent of the exception being created, or <code>null</code> if top-level
+     * @return The created exception
+     */
+    public static Throwables register(String id, Throwables parent)
+    {
+        Throwables exc = new Throwables(id, parent);
+        byId.put(id, exc);
+        return exc;
+    }
+
+    /**
+     * Creates a new exception.
+     * <p>Not suitable for creating exceptions that can't be caught.
+     * Use an {@link InternalExpressionException} for that
+     * @param id The exception's value as a {@link String}
+     */
+    public Throwables(String id, Throwables parent)
+    {
+        this.id = id;
+        this.parent = parent;
+    }
+
+    public static Throwables getTypeForException(String type)
+    {
+        Throwables properType = byId.get(type);
+        if (properType == null) throw new InternalExpressionException("Unknown exception type: "+type);
+        return properType;
+    }
+
+    /**
+     * Checks whether the given filter matches an instance of this exception, by checking equality
+     * with itself and possible parents.
+     * @param filter The type to check against
+     * @return Whether or not the given value matches this exception's hierarchy
+     */
+    public boolean isRelevantFor(String filter)
+    {
+        return (id.equals(filter) || (parent != null && parent.isRelevantFor(filter)));
+    }
+
+    public boolean isUserException()
+    {
+        return this == USER_DEFINED || parent == USER_DEFINED;
+    }
+
+    /**
+     * Returns the throwable type
+     * @return The type of this exception
+     */
+    public String getId() {
+        return id;
+    }
+}

src/main/java/carpet/script/language/ControlFlow.java

@@ -5,8 +5,17 @@ import carpet.script.Expression;
 import carpet.script.LazyValue;
 import carpet.script.exception.ExitStatement;
 import carpet.script.exception.InternalExpressionException;
+import carpet.script.exception.ProcessedThrowStatement;
 import carpet.script.exception.ThrowStatement;
+import carpet.script.exception.Throwables;
+import carpet.script.value.ListValue;
+import carpet.script.value.MapValue;
+import carpet.script.value.NumericValue;
+import carpet.script.value.StringValue;
 import carpet.script.value.Value;
+import com.google.common.collect.ImmutableMap;
+
+import java.util.stream.Collectors;
 
 public class ControlFlow {
     public static void apply(Expression expression) // public just to get the javadoc right
@@ -42,26 +51,98 @@ public class ControlFlow {
 
         expression.addFunction("exit", (lv) -> { throw new ExitStatement(lv.size()==0?Value.NULL:lv.get(0)); });
 
-        expression.addFunction("throw", (lv)-> {throw new ThrowStatement(lv.size()==0?Value.NULL:lv.get(0)); });
+        expression.addLazyFunction("throw", -1, (c, t, lv)-> 
+        {
+            switch (lv.size()) 
+            {
+                case 0:
+                    throw new ThrowStatement(Value.NULL, Throwables.USER_DEFINED);
+                case 1:
+                    throw new ThrowStatement(lv.get(0).evalValue(c), Throwables.USER_DEFINED );
+                case 2:
+                    throw new ThrowStatement(lv.get(1).evalValue(c), Throwables.getTypeForException(lv.get(0).evalValue(c).getString()));
+                case 3:
+                    throw new ThrowStatement(lv.get(2).evalValue(c), Throwables.getTypeForException(lv.get(1).evalValue(c).getString()), lv.get(0).evalValue(c).getString());
+                default:
+                    throw new InternalExpressionException("throw() can't accept more than 3 parameters");
+            }
+        });
 
         expression.addLazyFunction("try", -1, (c, t, lv) ->
         {
             if (lv.size()==0)
-                throw new InternalExpressionException("'try' needs at least an expression block");
+                throw new InternalExpressionException("'try' needs at least an expression block, and either a catch_epr, or a number of pairs of filters and catch_expr");
             try
             {
                 Value retval = lv.get(0).evalValue(c, t);
                 return (c_, t_) -> retval;
             }
-            catch (ThrowStatement ret)
+            catch (ProcessedThrowStatement ret)
             {
                 if (lv.size() == 1)
+                {
+                    if (!ret.thrownExceptionType.isUserException())
+                        throw ret;
                     return (c_, t_) -> Value.NULL;
+                }
+                if (lv.size() > 3 && lv.size() % 2 == 0)
+                {
+                    throw new InternalExpressionException("Try-catch block needs the code to run, and either a catch expression for user thrown exceptions, or a number of pairs of filters and catch expressions");
+                }
+                
+                Value val = null; // This is always assigned at some point, just the compiler doesn't know
+                
                 LazyValue __ = c.getVariable("_");
-                c.setVariable("_", (__c, __t) -> ret.retval.reboundedTo("_"));
-                Value val = lv.get(1).evalValue(c, t);
-                c.setVariable("_",__);
-                return (c_, t_) -> val;
+                c.setVariable("_", (__c, __t) -> ret.data.reboundedTo("_"));
+                LazyValue _trace = c.getVariable("_trace");
+                c.setVariable("_trace", (__c, __t) -> MapValue.wrap(ImmutableMap.of(
+                        StringValue.of("stack"), ListValue.wrap(ret.stack.stream().map(f -> ListValue.of(
+                                StringValue.of(f.getModule().getName()),
+                                StringValue.of(f.getString()),
+                                NumericValue.of(f.getToken().lineno+1),
+                                NumericValue.of(f.getToken().linepos+1)
+                        )).collect(Collectors.toList())),
+
+                        StringValue.of("locals"), MapValue.wrap(ret.context.variables.entrySet().stream().filter(e -> !e.getKey().equals("_trace")).collect(Collectors.toMap(
+                                e -> StringValue.of(e.getKey()),
+                                e -> e.getValue().evalValue(ret.context)
+                        ))),
+                        StringValue.of("token"), ListValue.of(
+                                StringValue.of(ret.token.surface),
+                                NumericValue.of(ret.token.lineno+1),
+                                NumericValue.of(ret.token.linepos+1)
+                        )
+                )));
+
+                if (lv.size() == 2)
+                {
+                    if (ret.thrownExceptionType.isUserException())
+                        val = lv.get(1).evalValue(c, t);
+                }
+                else
+                {
+                    int pointer = 1;
+                    while (pointer < lv.size() -1)
+                    {
+                        if (ret.thrownExceptionType.isRelevantFor(lv.get(pointer).evalValue(c).getString()))
+                        {
+                            val = lv.get(pointer + 1).evalValue(c, t);
+                            break;
+                        }
+                        pointer += 2;
+                    }
+                }
+                c.setVariable("_", __);
+                if (_trace != null)
+                    c.setVariable("_trace", _trace);
+                else
+                    c.delVariable("_trace");
+                if (val == null)  // not handled
+                {
+                    throw ret;
+                }
+                Value retval = val;
+                return (c_, t_) -> retval;
             }
         });
     }

src/main/java/carpet/script/utils/ShapeDispatcher.java

@@ -4,6 +4,8 @@ import carpet.CarpetSettings;
 import carpet.network.ServerNetworkHandler;
 import carpet.script.CarpetContext;
 import carpet.script.exception.InternalExpressionException;
+import carpet.script.exception.ThrowStatement;
+import carpet.script.exception.Throwables;
 import carpet.script.language.Sys;
 import carpet.script.value.BlockValue;
 import carpet.script.value.EntityValue;
@@ -156,7 +158,7 @@ public class ShapeDispatcher
         }
         catch (CommandSyntaxException e)
         {
-            throw new InternalExpressionException("No such particle: "+name);
+            throw new ThrowStatement(name, Throwables.UNKNOWN_PARTICLE);
         }
         particleCache.put(name, particle);
         return particle;

src/main/java/carpet/script/value/BlockValue.java

@@ -2,6 +2,9 @@ package carpet.script.value;
 
 import carpet.script.CarpetContext;
 import carpet.script.exception.InternalExpressionException;
+import carpet.script.exception.ThrowStatement;
+import carpet.script.exception.Throwables;
+
 import com.mojang.brigadier.StringReader;
 import com.mojang.brigadier.exceptions.CommandSyntaxException;
 import net.minecraft.block.BlockState;
@@ -73,7 +76,7 @@ public class BlockValue extends Value
         catch (CommandSyntaxException ignored)
         {
         }
-        throw new InternalExpressionException("Cannot parse block: "+str);
+        throw new ThrowStatement(str, Throwables.UNKNOWN_BLOCK);
     }
 
     public static BlockPos locateBlockPos(CarpetContext c, int xpos, int ypos, int zpos)

src/main/java/carpet/script/value/FunctionValue.java

@@ -215,7 +215,6 @@ public class FunctionValue extends Value implements Fluff.ILazyFunction
 
         }
         Value retVal;
-        boolean rethrow = false;
         try
         {
             retVal = body.evalValue(newFrame, type); // todo not sure if we need to propagete type / consider boolean context in defined functions - answer seems ye
@@ -228,15 +227,6 @@ public class FunctionValue extends Value implements Fluff.ILazyFunction
         {
             retVal = returnStatement.retval;
         }
-        catch (ThrowStatement throwStatement) // might not be really necessary
-        {
-            retVal = throwStatement.retval;
-            rethrow = true;
-        }
-        if (rethrow)
-        {
-            throw new ThrowStatement(retVal);
-        }
         Value otherRetVal = retVal;
         return (cc, tt) -> otherRetVal;
     }

src/main/java/carpet/script/value/NBTSerializableValue.java

@@ -4,6 +4,8 @@ import carpet.fakes.InventoryBearerInterface;
 import carpet.script.CarpetContext;
 import carpet.script.LazyValue;
 import carpet.script.exception.InternalExpressionException;
+import carpet.script.exception.ThrowStatement;
+import carpet.script.exception.Throwables;
 import carpet.script.utils.EquipmentInventory;
 import com.mojang.brigadier.StringReader;
 import com.mojang.brigadier.exceptions.CommandSyntaxException;
@@ -297,7 +299,7 @@ public class NBTSerializableValue extends Value implements ContainerValueInterfa
         }
         catch (CommandSyntaxException e)
         {
-            throw new InternalExpressionException("Incorrect item: "+itemString);
+            throw new ThrowStatement(itemString, Throwables.UNKNOWN_ITEM);
         }
     }
 

src/main/java/carpet/script/value/ValueConversions.java

@@ -2,6 +2,8 @@ package carpet.script.value;
 
 import carpet.fakes.BlockPredicateInterface;
 import carpet.script.exception.InternalExpressionException;
+import carpet.script.exception.ThrowStatement;
+import carpet.script.exception.Throwables;
 import carpet.utils.BlockInfo;
 import net.minecraft.block.BlockState;
 import net.minecraft.block.MapColor;
@@ -158,7 +160,7 @@ public class ValueConversions
                         }
                     }
                     if (dim == null)
-                        throw new InternalExpressionException("Incorrect dimension string: "+dimString);
+                        throw new ThrowStatement(dimString, Throwables.UNKNOWN_DIMENSION);
                     return server.getWorld(dim);
             }
         }