Fix the behavior for append

examples/Example JN Problem.ipynb

@@ -2,19 +2,15 @@
  "cells": [
   {
    "cell_type": "markdown",
-   "metadata": {
-    "deletable": false
-   },
+   "metadata": {},
    "source": [
     "Create, initialize, and print an integer variable that represents your age."
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 22,
-   "metadata": {
-    "deletable": false
-   },
+   "execution_count": 10,
+   "metadata": {},
    "outputs": [],
    "source": [
     "from pedal.plugins.grade_magic import load_ipython_extension\n",
@@ -24,9 +20,8 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 23,
+   "execution_count": 11,
    "metadata": {
-    "deletable": false,
     "scrolled": true
    },
    "outputs": [
@@ -36,7 +31,7 @@
        "'sleep'"
       ]
      },
-     "execution_count": 23,
+     "execution_count": 11,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -60,10 +55,8 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 24,
+   "execution_count": 12,
    "metadata": {
-    "deletable": false,
-    "editable": false,
     "scrolled": false
    },
    "outputs": [
@@ -109,8 +102,8 @@
        "    $(last.element).animate({\"background-color\": \"#F6FAFF\"}, 1000);\n",
        "}\n",
        "\n",
-       "on_run_code.push(\"from pedal.plugins.grade_magic import blockpy_grade\");\n",
-       "on_run_code.push(\"print(blockpy_grade(1, student_code))\");\n",
+       "on_run_code.push(\"from pedal.plugins.grade_magic import execute_on_run_code\");\n",
+       "on_run_code.push('print(execute_on_run_code(\"gently(\\\\\\\"TEST\\\\\\\")\", student_code))');\n",
        "\n",
        "on_run_code = on_run_code.join(\"\\n\");\n",
        "console.log(on_run_code);\n",
@@ -150,7 +143,8 @@
     }
    ],
    "source": [
-    "%grade_blockpy 1"
+    "%%grade\n",
+    "gently(\\\"TEST\\\")"
    ]
   }
  ],
@@ -172,7 +166,7 @@
    "pygments_lexer": "ipython3",
    "version": "3.5.4"
   },
-  "student_mode": true
+  "student_mode": false
  },
  "nbformat": 4,
  "nbformat_minor": 2

pedal/plugins/grade_magic.py

@@ -167,7 +167,7 @@ def execute_on_run_code(on_run, student_code):
 # If the %grade magic is used, we run the code directly.
 LOCAL_GRADE = r'''
 on_run_code.push("from pedal.plugins.grade_magic import execute_on_run_code");
-on_run_code.push("print(execute_on_run_code({on_run_code}, student_code))");
+on_run_code.push('print(execute_on_run_code({on_run_code}, student_code))');
 '''
 
 # If the %grade_blockpy magic is used, we need to get the on_run from blockpy.

pedal/tifa/messages.py

@@ -96,23 +96,23 @@ def _format_message(issue, data):
                 "was used. One of the times that you gave <code>{name}</code> "
                 "a value was incorrect."
                 ).format(line=data['position']['line'], name=data['name'])
-    elif issue == 'Iterating over empty list':
+    elif issue == 'Iterating over non-list':
         if 'name' not in data or data['name'] is None:
             expression = "expression"
         else:
             expression = "variable <code>{}</code>".format(data['name'])
-        return ("The {expression} was set as an empty list, "
-                "and then you attempted to use it in an iteration on line "
-                "{line}. You should only iterate over non-empty lists."
+        return ("The {expression} is not a list, but you used "
+                "it in the iteration on line {line}. You should only iterate "
+                "over sequences like lists."
                 ).format(line=data['position']['line'], expression=expression)
-    elif issue == 'Iterating over non-list':
+    elif issue == 'Iterating over empty list':
         if 'name' not in data or data['name'] is None:
             expression = "expression"
         else:
             expression = "variable <code>{}</code>".format(data['name'])
-        return ("The {expression} is not a list, but you used "
-                "it in the iteration on line {line}. You should only iterate "
-                "over sequences like lists."
+        return ("The {expression} was set as an empty list, "
+                "and then you attempted to use it in an iteration on line "
+                "{line}. You should only iterate over non-empty lists."
                 ).format(line=data['position']['line'], expression=expression)
     elif issue == 'Incompatible types':
         op = OPERATION_DESCRIPTION.get(data['operation'].__class__, 

pedal/tifa/tifa.py

@@ -620,7 +620,6 @@ def visit_If(self, node):
                 self.report_issue("Malformed Conditional")
 
         # Visit the bodies
-        #this_path_id = self.path_id
         this_path_id = self.path_chain[0]
         if_path = Tifa.NewPath(self, this_path_id, "i")
         with if_path:
@@ -1158,7 +1157,6 @@ def __enter__(self):
             self.tifa.name_map[self.id] = {}
             self.tifa.path_parents[self.id] = self.origin_path
         def __exit__(self, type, value, traceback):
-            val = self.tifa.path_chain[0]
             self.tifa.path_names.pop()
             self.tifa.path_chain.pop(0)
 

pedal/tifa/type_definitions.py

@@ -157,9 +157,10 @@ def load_attr(self, attr, tifa, callee=None, callee_position=None):
         if attr == 'append':
             def _append(tifa, function_type, callee, args, position):
                 if args:
+                    cloned_type = ListType(subtype=args[0].clone(),
+                                           empty=False)
                     if callee:
-                        tifa.append_variable(callee, ListType(args[0].clone()), 
-                                             position)
+                        tifa.append_variable(callee, cloned_type, position)
                     self.empty = False
                     self.subtype = args[0]
             return FunctionType(_append, 'append')

tests/example_pipeline.py

@@ -38,7 +38,7 @@
 from pedal.report import *
 report.set_source(STUDENT_SOURCE)
     # get_output, set_success, gently, explain
-from pedal.tifa import tifa_analysis()
+from pedal.tifa import tifa_analysis
     # tifa_analysis
 from pedal.mistakes import mistakes
     # misconceptions

tests/test_tifa.py

@@ -278,6 +278,10 @@
     'int_membership_in_comprehension':
         ['4 in (a for a in [1,2,3])', ['Unused Variable', "Incompatible types"], []],
 
+    'prevent_empty_iteration_in_appended_list':
+        ['eles = [1,2,3]\nx = []\nfor ele in eles:\n    x.append(ele)\nfor e2 in x:\n    e2+1', 
+            ['Iterating over empty list'], []],
+
     # Built-in modules
     'import_string_letters':
         ['import string\nstring.letters+""', ['Incompatible types'], []],