Minor improvements to scarpet annotation API (#1239)

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

@@ -481,9 +481,9 @@ public class Expression
     }
 
 
-    public void addLazyFunction(String name, int num_params, TriFunction<Context, Context.Type, List<LazyValue>, LazyValue> fun)
+    public void addLazyFunction(String name, int numParams, TriFunction<Context, Context.Type, List<LazyValue>, LazyValue> fun)
     {
-        functions.put(name, new AbstractLazyFunction(num_params, name)
+        functions.put(name, new AbstractLazyFunction(numParams, name)
         {
             @Override
             public boolean pure() {
@@ -499,8 +499,11 @@ public class Expression
             public LazyValue lazyEval(Context c, Context.Type i, Expression e, Tokenizer.Token t, List<LazyValue> lazyParams)
             {
                 ILazyFunction.checkInterrupts();
-                if (num_params >= 0 && lazyParams.size() != num_params)
-                    throw new InternalExpressionException("'"+name+"' requires "+num_params+" parameters, "+lazyParams.size()+" provided.");
+                if (numParams >= 0 && lazyParams.size() != numParams)
+                {
+                    String error = "Function '"+name+"' requires "+numParams+" arguments, got "+lazyParams.size()+". ";
+                    throw new InternalExpressionException(error + (fun instanceof Fluff.UsageProvider up ? up.getUsage() : ""));
+                }
 
                 try
                 {

src/main/java/carpet/script/Fluff.java

@@ -30,6 +30,8 @@ public abstract class Fluff
     @FunctionalInterface
     public interface SexFunction<A, B, C, D, E, F, R> { R apply(A a, B b, C c, D d, E e, F f);}
 
+    public interface UsageProvider { String getUsage();}
+
     public interface EvalNode
     {
         /**

src/main/java/carpet/script/annotation/AnnotationParser.java

@@ -21,6 +21,7 @@ import carpet.script.Context;
 import carpet.script.Expression;
 import carpet.script.Fluff.AbstractLazyFunction;
 import carpet.script.Fluff.TriFunction;
+import carpet.script.Fluff.UsageProvider;
 import carpet.script.exception.InternalExpressionException;
 import carpet.script.LazyValue;
 import carpet.script.value.Value;
@@ -73,6 +74,7 @@ import it.unimi.dsi.fastutil.objects.ObjectArrayList;
  */
 public final class AnnotationParser
 {
+    static final int UNDEFINED_PARAMS = -2;
     private static final List<ParsedFunction> functionList = new ArrayList<>();
 
     /**
@@ -90,8 +92,8 @@ public final class AnnotationParser
      * {@link InternalExpressionException}).
      * Basically, it's fine as long as you don't add a {@code throws} declaration to your methods.</li>
      * <li>Varargs (or effectively varargs) annotated methods must explicitly declare a maximum number of parameters to ingest in the {@link ScarpetFunction} 
-     * annotation. They can still declare an unlimited amount by setting that maximum to {@code -1}. "Effectively varargs" means a function that has 
-     * a parameter using/requiring a {@link ValueConverter} that has declared {@link ValueConverter#consumesVariableArgs()}.</li>
+     * annotation. They can still declare an unlimited amount by setting that maximum to {@link ScarpetFunction#UNLIMITED_PARAMS}. "Effectively varargs" 
+     * means a function that has at least a parameter requiring a {@link ValueConverter} that has declared {@link ValueConverter#consumesVariableArgs()}.</li>
      * <li>Annotated methods must not have a parameter with generics as the varargs parameter. This is just because it was painful for me (altrisi) and 
      * didn't want to support it. Those will crash with a {@code ClassCastException}</li>
      * </ul>
@@ -141,7 +143,7 @@ public final class AnnotationParser
             expr.addLazyFunction(function.name, function.scarpetParamCount, function);
     }
 
-    private static class ParsedFunction implements TriFunction<Context, Context.Type, List<LazyValue>, LazyValue>
+    private static class ParsedFunction implements TriFunction<Context, Context.Type, List<LazyValue>, LazyValue>, UsageProvider
     {
         private final String name;
         private final boolean isMethodVarArgs;
@@ -186,14 +188,14 @@ public final class AnnotationParser
             if (this.isEffectivelyVarArgs)
             {
                 maxParams = method.getAnnotation(ScarpetFunction.class).maxParams();
-                if (maxParams == -2)
-                    throw new IllegalArgumentException("No maximum number of params specified for " + name + ", use -1 for unlimited. "
+                if (maxParams == UNDEFINED_PARAMS)
+                    throw new IllegalArgumentException("No maximum number of params specified for " + name + ", use ScarpetFunction.UNLIMITED_PARAMS for unlimited. "
                             + "Provided in " + instance.getClass());
+                if (maxParams == ScarpetFunction.UNLIMITED_PARAMS)
+                    maxParams = Integer.MAX_VALUE;
                 if (maxParams < this.minParams)
                     throw new IllegalArgumentException("Provided maximum number of params for " + name + " is smaller than method's param count."
                             + "Provided in " + instance.getClass());
-                if (maxParams == -1)
-                    maxParams = Integer.MAX_VALUE;
             }
             this.maxParams = maxParams;
 
@@ -293,7 +295,8 @@ public final class AnnotationParser
             return params;
         }
 
-        private String getUsage()
+        @Override
+        public String getUsage()
         {
             // Possibility: More descriptive messages using param.getName()? Would need changing gradle setup to keep those
             StringBuilder builder = new StringBuilder("Usage: '");

src/main/java/carpet/script/annotation/ScarpetFunction.java

@@ -51,6 +51,11 @@ import carpet.script.value.Value;
 @Retention(RUNTIME)
 public @interface ScarpetFunction
 {
+    /**
+     * <p>Used to define that this {@link ScarpetFunction} can accept an unlimited number of parameters</p>
+     */
+    public static final int UNLIMITED_PARAMS = -1;
+
     /**
      * <p>If the function can accept a variable number of parameters, either by declaring its last parameter as a varargs parameter or by having one
      * of their parameters use a converter that consumes a variable number of arguments, this must define the maximum number of parameters this
@@ -65,11 +70,11 @@ public @interface ScarpetFunction
      * consider that those can take either a single triple of values or 3 independent values, that would be counted in the maximum number of
      * parameters.</p>
      * 
-     * <p>Use -1 to specify an unlimited number of parameters.</p>
+     * <p>Use {@link ScarpetFunction#UNLIMITED_PARAMS} to allow an unlimited number of parameters.</p>
      * 
      * @return The maximum number of parameters this function can accept
      */
-    int maxParams() default -2;
+    int maxParams() default AnnotationParser.UNDEFINED_PARAMS;
 
     /**
      * <p>Defines the Context Type that will be used when evaluating arguments to annotated methods.</p>

src/main/java/carpet/script/annotation/ValueConverter.java

@@ -162,13 +162,13 @@ public interface ValueConverter<R>
      *           constraints as {@link #convert(Value)}</p>
      * @param valueIterator An {@link Iterator} holding the {@link Value} to convert in next position
      * @param context       The {@link Context} this function has been called with. This was used when this passed lazy values instead in order to
-     *                      evaluate, now it's used to get the context. It is now ignored by the default implementation
-     * @param theLazyT      The {@code t} that the original function was called with. It is ignored by the default implementation.
+     *                      evaluate, now it's used to get the context
+     * @param contextType   The {@link Context.Type} that the original function was called with
      * @return The next {@link Value} (s) converted to the type {@code <R>} of this {@link ValueConverter}
      * @implNote This method's default implementation runs the {@link #convert(Value)} function in the next {@link Value} ignoring {@link Context} and
      *           {@code theLazyT}.
      */
-    default public R checkAndConvert(Iterator<Value> valueIterator, Context context, Context.Type theLazyT)
+    default public R checkAndConvert(Iterator<Value> valueIterator, Context context, Context.Type contextType)
     {
         if (!valueIterator.hasNext())
             return null;