allow raising exceptions with causes more easily

Author: timfel

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/modules/BuiltinFunctions.java

@@ -1278,7 +1278,7 @@ public Object next(Object iterator, PNone defaultObject,
                 return next.execute(iterator);
             } catch (PException e) {
                 e.expectAttributeError(errorProfile);
-                throw raise(TypeError, "'%p' object is not an iterator", iterator);
+                throw raise(TypeError, e.getExceptionObject(), "'%p' object is not an iterator", iterator);
             }
         }
 

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/nodes/PNodeWithContext.java

@@ -45,6 +45,7 @@
 import com.oracle.graal.python.builtins.objects.exception.PBaseException;
 import com.oracle.graal.python.builtins.objects.type.LazyPythonClass;
 import com.oracle.graal.python.builtins.objects.type.PythonClass;
+import com.oracle.graal.python.nodes.attributes.WriteAttributeToObjectNode;
 import com.oracle.graal.python.runtime.PythonContext;
 import com.oracle.graal.python.runtime.PythonCore;
 import com.oracle.graal.python.runtime.exception.PException;
@@ -62,6 +63,7 @@
 
 public abstract class PNodeWithContext extends Node {
     @Child private PythonObjectFactory factory;
+    @Child private WriteAttributeToObjectNode writeCause;
     @CompilationFinal private ContextReference<PythonContext> contextRef;
 
     protected final PythonObjectFactory factory() {
@@ -88,6 +90,17 @@ public PException raise(LazyPythonClass exceptionType) {
         throw raise(factory().createBaseException(exceptionType));
     }
 
+    public final PException raise(PythonBuiltinClassType type, PBaseException cause, String format, Object... arguments) {
+        assert format != null;
+        PBaseException baseException = factory().createBaseException(type, format, arguments);
+        if (writeCause == null) {
+            CompilerDirectives.transferToInterpreterAndInvalidate();
+            writeCause = insert(WriteAttributeToObjectNode.create());
+        }
+        writeCause.execute(baseException, SpecialAttributeNames.__CAUSE__, cause);
+        throw raise(baseException);
+    }
+
     public final PException raise(PythonBuiltinClassType type, String format, Object... arguments) {
         assert format != null;
         throw raise(factory().createBaseException(type, format, arguments));