show a nice error message if the program contains non-exportable blocks

1 files changed, 10 insertions, 12 deletions

diff --git a/TurtleArt/taexportpython.py b/TurtleArt/taexportpython.py
index 52216d9..4688ea9 100644
--- a/TurtleArt/taexportpython.py
+++ b/TurtleArt/taexportpython.py
@@ -27,7 +27,7 @@ import util.codegen as codegen
 
 #from ast_pprint import * # only used for debugging, safe to comment out
 
-from taprimitive import Primitive
+from taprimitive import (Primitive, PyExportError)
 from tautils import (debug_output, find_top_block)
 
 
@@ -126,12 +126,17 @@ def _walk_action_stack(top_block, lc):
     arg_asts = []
 
     def _finish_off(block):
+        """ Convert block to an AST and add it to the ast_list. Raise a
+        PyExportError on failure. """
         prim = lc.get_prim_callable(block.primitive)
-        # TODO fail gracefully if primitive is not a Primitive object
+        # fail gracefully if primitive is not a Primitive object
         if not isinstance(prim, Primitive):
-            raise TypeError("cannot export block " + repr(block))
+            raise PyExportError("block is not exportable", block=block)
         if prim.export_me:
-            new_ast = prim.get_ast(*arg_asts)
+            try:
+                new_ast = prim.get_ast(*arg_asts)
+            except ValueError:
+                raise PyExportError("error while exporting block", block=block)
             if isinstance(new_ast, (list, tuple)):
                 ast_list.extend(new_ast)
             else:
@@ -182,7 +187,7 @@ def _value_to_ast(value):
     elif isinstance(value, basestring):
         return ast.Str(value)
     else:
-        raise TypeError("unknown type of raw value: " + repr(type(value)))
+        raise ValueError("unknown type of raw value: " + repr(type(value)))
 
 def _make_identifier(name):
     """ Turn name into a Python identifier name by replacing illegal
@@ -204,10 +209,3 @@ def _indent(code, num_levels=1):
     return linesep.join(new_line_list)
 
 
-
-if __name__ == "__main__":
-    f = open("/bigrepos/sugar-labs/ta-python-export-dev/exported.py", "w")
-    f.write(_action_stack_to_python([]))
-    f.close()
-
-