From b5606471d456a4d08ac18a97b58e353938ce39f9 Mon Sep 17 00:00:00 2001
From: Michael Williamson <mike@zwobble.org>
Date: Sun, 25 Jan 2015 15:26:01 +0000
Subject: Allow empty HTML paths

---
 mammoth/html_paths.py                    |  2 ++
 mammoth/style_reader/html_path_reader.py | 13 +++++++++++--
 tests/style_reader_tests.py              |  8 ++++++++
 3 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/mammoth/html_paths.py b/mammoth/html_paths.py
index 887288b..1428015 100644
--- a/mammoth/html_paths.py
+++ b/mammoth/html_paths.py
@@ -15,3 +15,5 @@ def element(names, class_names=None, fresh=None):
 
 HtmlPath = collections.namedtuple("HtmlPath", ["elements"])
 HtmlPathElement = collections.namedtuple("HtmlPathElement", ["names", "class_names", "fresh"])
+
+empty = path([])
diff --git a/mammoth/style_reader/html_path_reader.py b/mammoth/style_reader/html_path_reader.py
index b508f59..20666d4 100644
--- a/mammoth/style_reader/html_path_reader.py
+++ b/mammoth/style_reader/html_path_reader.py
@@ -9,6 +9,13 @@ def read_html_path(string):
 
 
 def read_html_path_node(path_node):
+    if path_node.children:
+        return _read_html_path_elements_node(path_node.children[0])
+    else:
+        return html_paths.empty
+
+
+def _read_html_path_elements_node(path_node):
     elements = [
         _read_element_node(child)
         for child in _repeated_children_with_separator(path_node, has_whitespace=True)
@@ -60,7 +67,9 @@ def _repeated_children_with_separator(node, has_whitespace):
 
 grammar_text = r"""
 
-html_path = element (whitespace* ">" whitespace* element)*
+html_path = html_path_elements?
+
+html_path_elements = element (whitespace* ">" whitespace* element)*
 
 element = tag_names class_name* fresh?
 
@@ -70,7 +79,7 @@ class_name = "." identifier
 
 fresh = ":fresh"
 
-identifier = ~"[A-Z0-9]*"i
+identifier = ~"[A-Z0-9]+"i
 
 whitespace = ~"\s"*
 
diff --git a/tests/style_reader_tests.py b/tests/style_reader_tests.py
index c4ac513..464cb4a 100644
--- a/tests/style_reader_tests.py
+++ b/tests/style_reader_tests.py
@@ -6,12 +6,20 @@ from mammoth.style_reader import read_html_path, read_document_matcher, read_sty
 
 @istest
 class ReadHtmlPathTests(object):
+    @istest
+    def can_read_empty_path(self):
+        assert_equal(
+            html_paths.empty,
+            read_html_path("")
+        )
+
     @istest
     def can_read_single_element(self):
         assert_equal(
             html_paths.path([html_paths.element(["p"])]),
             read_html_path("p")
         )
+
     
     @istest
     def can_read_choice_of_two_elements(self):
-- 
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