added custom context to be used in optimization evaluations that should expose all programmers issues, while allowing reporting errors to the error snooping entity. Fixes #875

src/main/java/carpet/script/Context.java

@@ -1,5 +1,6 @@
 package carpet.script;
 
+import carpet.script.exception.InternalExpressionException;
 import carpet.script.value.Value;
 
 import java.util.HashMap;
@@ -83,4 +84,63 @@ public class Context
     {
         return new Context(this.host);
     }
+    public ScriptHost.ErrorSnooper getErrorSnooper()
+    {
+        return host.errorSnooper;
+    }
+
+
+    /**
+     * immutable context only for reason on reporting access violations in evaluating expressions in optimizization
+     * mode detecting any potential violations that may happen on the way
+     */
+    public static class ContextForErrorReporting extends Context
+    {
+        public ScriptHost.ErrorSnooper optmizerEerrorSnooper;
+        public ContextForErrorReporting(Context parent)
+        {
+            super(null);
+            optmizerEerrorSnooper =  parent.host.errorSnooper;
+        }
+
+        @Override
+        public ScriptHost.ErrorSnooper getErrorSnooper()
+        {
+            return optmizerEerrorSnooper;
+        }
+
+        public void badProgrammer()
+        {
+            throw new InternalExpressionException("Attempting to access the execution context while optimizing the code;" +
+                    " This is not the problem with your code, but the error cause by improper use of code compile optimizations" +
+                    "of scarpet authors. Please report this issue directly to the scarpet issue tracker");
+
+        }
+        @Override
+        public LazyValue getVariable(String name) { badProgrammer(); return null;}
+
+        @Override
+        public void setVariable(String name, LazyValue lv) { badProgrammer(); }
+
+        @Override
+        public void delVariable(String variable) { badProgrammer(); }
+
+        @Override
+        public void removeVariablesMatching(String varname) { badProgrammer(); }
+
+        @Override
+        public Context with(String variable, LazyValue lv) { badProgrammer(); return this; }
+
+        @Override
+        public Set<String> getAllVariableNames() { badProgrammer(); return null;}
+
+        @Override
+        public Context recreate() { badProgrammer(); return null;}
+
+        @Override
+        protected void initialize() { badProgrammer();}
+
+        @Override
+        public Context duplicate() { badProgrammer(); return null;}
+    }
 }

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

@@ -1072,6 +1072,7 @@ public class Expression
         if (!CarpetSettings.scriptsOptimization)
             return root.op;
 
+        Context optimizeOnlyContext = new Context.ContextForErrorReporting(context);
         CarpetScriptServer.LOG.info("Input code size for "+getModuleName()+": " + treeSize(root) + " nodes, " + treeDepth(root) + " deep");
 
         boolean changed = true;
@@ -1088,13 +1089,13 @@ public class Expression
             while (true) {
                 int tree_size = treeSize(root);
                 int tree_depth = treeDepth(root);
-                boolean optimized = optimizeTree(context, root, Context.Type.NONE, 0);
+                boolean optimized = optimizeTree(optimizeOnlyContext, root, Context.Type.NONE, 0);
                 if (!optimized) break;
                 changed = true;
                 CarpetScriptServer.LOG.info("Optimized from " + tree_size + " nodes, " + tree_depth + " code depth to " + treeSize(root) + " nodes, " + treeDepth(root) + " code depth");
             }
         }
-        return extractOp(context, root, Context.Type.NONE);
+        return extractOp(optimizeOnlyContext, root, Context.Type.NONE);
     }
 
     private int treeSize(ExpressionNode node)
@@ -1222,25 +1223,25 @@ public class Expression
                     Value val = ((LazyValue.Constant) arg.op).get();
                     args.add((c, t) -> val);
                 }
-                else args.add((c, t) -> arg.op.evalValue(null, requestedType));
+                else args.add((c, t) -> arg.op.evalValue(ctx, requestedType));
             } catch (NullPointerException npe) {
                 throw new ExpressionException(ctx, this, node.token, "Attempted to evaluate context free expression");
             }
         }
         // applying argument unpacking
-        args= AbstractLazyFunction.lazify(AbstractLazyFunction.unpackLazy(args, null, requestedType));
+        args= AbstractLazyFunction.lazify(AbstractLazyFunction.unpackLazy(args, ctx, requestedType));
         Value result;
         if (operation instanceof ILazyFunction)
         {
-            result = ((ILazyFunction) operation).lazyEval(null, expectedType, this, node.token, args).evalValue(null, expectedType);
+            result = ((ILazyFunction) operation).lazyEval(ctx, expectedType, this, node.token, args).evalValue(null, expectedType);
         }
         else if (args.size() == 1)
         {
-            result = ((ILazyOperator)operation).lazyEval(null, expectedType, this, node.token, args.get(0), null).evalValue(null, expectedType);
+            result = ((ILazyOperator)operation).lazyEval(ctx, expectedType, this, node.token, args.get(0), null).evalValue(null, expectedType);
         }
         else // args == 2
         {
-            result = ((ILazyOperator)operation).lazyEval(null, expectedType, this, node.token, args.get(0), args.get(1)).evalValue(null, expectedType);
+            result = ((ILazyOperator)operation).lazyEval(ctx, expectedType, this, node.token, args.get(0), args.get(1)).evalValue(null, expectedType);
         }
         node.op = LazyValue.ofConstant(result);
         //node.token.morph(Tokenizer.Token.TokenType.CONSTANT, node.token.surface);

src/main/java/carpet/script/ScriptHost.java

@@ -105,7 +105,12 @@ public abstract class ScriptHost
 
     public final Module main;
 
-    public Fluff.TriFunction<Expression, Tokenizer.Token, String, List<String>> errorSnooper = null;
+    @FunctionalInterface
+    public interface ErrorSnooper
+    {
+        List<String> apply(Expression expression, Tokenizer.Token token, String message);
+    }
+    public ErrorSnooper errorSnooper = null;
 
     protected ScriptHost(Module code, boolean perUser, ScriptHost parent)
     {

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

@@ -72,9 +72,9 @@ public class ExpressionException extends RuntimeException implements ResolvedExc
 
     synchronized static String makeMessage(Context c, Expression e, Tokenizer.Token t, String message) throws ExpressionException
     {
-        if (c.host.errorSnooper != null)
+        if (c.getErrorSnooper() != null)
         {
-            List<String> alternative = c.host.errorSnooper.apply(e, t, message);
+            List<String> alternative = c.getErrorSnooper().apply(e, t, message);
             if (alternative!= null)
             {
                 return String.join("\n", alternative);