imports and better error reporting and stacktraces

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

@@ -1,8 +1,10 @@
 package carpet.script.exception;
 
+import carpet.script.Context;
 import carpet.script.Expression;
 import carpet.script.Fluff;
 import carpet.script.Tokenizer;
+import carpet.script.value.FunctionValue;
 
 import java.util.ArrayList;
 import java.util.List;
@@ -13,38 +15,58 @@ import static carpet.script.ExpressionInspector.Expression_getName;
 /* The expression evaluators exception class. */
 public class ExpressionException extends RuntimeException
 {
-    public ExpressionException(String message)
+    public Context context;
+    public List<FunctionValue> stack = new ArrayList<>();
+    public ExpressionException(Context c, String message)
     {
-        super(message);
+        super(makeMessage(c, null, null, message));
+        context = c;
+    }
+
+    public ExpressionException(Context c, Expression e, Tokenizer.Token t, String message)
+    {
+        super(makeMessage(c, e, t, message));
+        context = c;
+    }
+    public ExpressionException(Context c, Expression e, Tokenizer.Token t, String message, List<FunctionValue> stack)
+    {
+        super(makeMessage(c, e, t, message));
+        this.stack.addAll(stack);
+        context = c;
     }
 
     private static Fluff.TriFunction<Expression, Tokenizer.Token, String, List<String>> errorMaker = (expr, token, errmessage) ->
     {
 
-        List<String> snippet = Expression_getExpressionSnippet(token, expr);
-        List<String> errMsg = new ArrayList<>(snippet);
-        if (snippet.size() != 1)
+        List<String> errMsg = new ArrayList<>();
+        if (expr != null && token != null)
         {
-            errmessage+= " at line "+(token.lineno+1)+", pos "+(token.linepos+1);
-        }
-        else
-        {
-            errmessage += " at pos "+(token.pos+1);
-        }
-        if (Expression_getName(expr) != null)
-        {
-            errmessage += " ("+Expression_getName(expr)+")";
+            List<String> snippet = Expression_getExpressionSnippet(token, expr);
+            errMsg.addAll(snippet);
+
+            if (snippet.size() != 1)
+            {
+                errmessage += " at line " + (token.lineno + 1) + ", pos " + (token.linepos + 1);
+            }
+            else
+            {
+                errmessage += " at pos " + (token.pos + 1);
+            }
+            if (Expression_getName(expr) != null)
+            {
+                errmessage += " (" + Expression_getName(expr) + ")";
+            }
+
         }
         errMsg.add(errmessage);
         return errMsg;
     };
-    public static Fluff.TriFunction<Expression, Tokenizer.Token, String, List<String>> errorSnooper = null;
 
-    static String makeMessage(Expression e, Tokenizer.Token t, String message) throws ExpressionException
+    static String makeMessage(Context c, Expression e, Tokenizer.Token t, String message) throws ExpressionException
     {
-        if (errorSnooper != null)
+        if (c.host.errorSnooper != null)
         {
-            List<String> alternative = errorSnooper.apply(e, t, message);
+            List<String> alternative = c.host.errorSnooper.apply(e, t, message);
             if (alternative!= null)
             {
                 return String.join("\n", alternative);
@@ -52,9 +74,4 @@ public class ExpressionException extends RuntimeException
         }
         return String.join("\n", errorMaker.apply(e, t, message));
     }
-
-    public ExpressionException(Expression e, Tokenizer.Token t, String message)
-    {
-        super(makeMessage(e, t, message));
-    }
 }