Small fix to Earley debuging

lark/parse_tree_builder.py

@@ -160,7 +160,7 @@ class AmbiguousExpander:
     """Deal with the case where we're expanding children ('_rule') into a parent but the children
        are ambiguous. i.e. (parent->_ambig->_expand_this_rule). In this case, make the parent itself
        ambiguous with as many copies as their are ambiguous children, and then copy the ambiguous children
-       into the right parents in the right places, essentially shifting the ambiguiuty up the tree."""
+       into the right parents in the right places, essentially shifting the ambiguity up the tree."""
     def __init__(self, to_expand, tree_class, node_builder):
         self.node_builder = node_builder
         self.tree_class = tree_class

lark/parsers/earley.py

@@ -297,6 +297,10 @@ class Parser:
         # symbol should have been completed in the last step of the Earley cycle, and will be in
         # this column. Find the item for the start_symbol, which is the root of the SPPF tree.
         solutions = [n.node for n in columns[-1] if n.is_complete and n.node is not None and n.s == start_symbol and n.start == 0]
+        if not solutions:
+            expected_tokens = [t.expect for t in to_scan]
+            raise UnexpectedEOF(expected_tokens)
+
         if self.debug:
             from .earley_forest import ForestToPyDotVisitor
             try:
@@ -307,10 +311,7 @@ class Parser:
                 debug_walker.visit(solutions[0], "sppf.png")
 
 
-        if not solutions:
-            expected_tokens = [t.expect for t in to_scan]
-            raise UnexpectedEOF(expected_tokens)
-        elif len(solutions) > 1:
+        if len(solutions) > 1:
             assert False, 'Earley should not generate multiple start symbol items!'
 
         if self.tree_class is not None:

lark/parsers/earley_forest.py

@@ -679,7 +679,10 @@ class ForestToPyDotVisitor(ForestVisitor):
 
     def visit(self, root, filename):
         super(ForestToPyDotVisitor, self).visit(root)
-        self.graph.write_png(filename)
+        try:
+            self.graph.write_png(filename)
+        except FileNotFoundError as e:
+            logger.error("Could not write png: ", e)
 
     def visit_token_node(self, node):
         graph_node_id = str(id(node))