fix: fail on unmatched tags

pystache/parser.py

@@ -17,15 +17,14 @@
 # TODO: add some unit tests for this.
 # TODO: add a test case that checks for spurious spaces.
 # TODO: add test cases for delimiters.
-def parse(template, delimiters=None):
+def parse(template, delimiters=None, raise_on_mismatch=False):
     """
     Parse a unicode template string and return a ParsedTemplate instance.
 
     Arguments:
-
       template: a unicode template string.
-
       delimiters: a 2-tuple of delimiters.  Defaults to the package default.
+      raise_on_mismatch: a boolean indicating whether to raise an exception when parsing fails.
 
     Examples:
 
@@ -36,7 +35,7 @@ def parse(template, delimiters=None):
     """
     if type(template) is not str:
         raise Exception('Template is not unicode: %s' % type(template))
-    parser = _Parser(delimiters)
+    parser = _Parser(delimiters, raise_on_mismatch=raise_on_mismatch)
     return parser.parse(template)
 
 
@@ -220,12 +219,14 @@ def render(self, engine, context):
 class _Parser(object):
     _delimiters = None
     _template_re = None
+    _raise_on_mismatch = False
 
-    def __init__(self, delimiters=None):
+    def __init__(self, delimiters=None, raise_on_mismatch=False):
         if delimiters is None:
             delimiters = defaults.DELIMITERS
 
         self._delimiters = delimiters
+        self._raise_on_mismatch = raise_on_mismatch
 
     def _compile_delimiters(self):
         self._template_re = _compile_template_re(self._delimiters)
@@ -237,17 +238,12 @@ def _change_delimiters(self, delimiters):
     def parse(self, template):
         """
         Parse a template string starting at some index.
-
         This method uses the current tag delimiter.
 
         Arguments:
-
           template: a unicode string that is the template to parse.
 
-          index: the index at which to start parsing.
-
         Returns:
-
           a ParsedTemplate instance.
 
         """
@@ -337,6 +333,10 @@ def parse(self, template):
 
             parsed_template.add(node)
 
+        # Some open/close tags were mismatched.
+        if self._raise_on_mismatch and states:
+            raise ParsingError('Tag mismatch.')
+
         # Avoid adding spurious empty strings to the parse tree.
         if start_index != len(template):
             parsed_template.add(template[start_index:])

pystache/tests/test_parser.py

@@ -8,19 +8,50 @@
 import unittest
 
 from pystache.defaults import DELIMITERS
-from pystache.parser import _compile_template_re as make_re
+from pystache.parser import _compile_template_re as make_re, parse, ParsingError
 
 
 class RegularExpressionTestCase(unittest.TestCase):
-
     """Tests the regular expression returned by _compile_template_re()."""
 
     def test_re(self):
         """
         Test getting a key from a dictionary.
-
         """
         re = make_re(DELIMITERS)
         match = re.search("b  {{test}}")
 
         self.assertEqual(match.start(), 1)
+
+
+class ParseTestCase(unittest.TestCase):
+    """Tests the parse() function."""
+
+    def test_parse_okay(self):
+        """
+        Test parsing templates in the cases there are no errors.
+        """
+        ts = [
+            '<div>{{>A}}</div>',
+            '{{#A}}<div> some text</div>',
+            '{{^A}}<div> some text</div>{{/A}}',
+            '{{#A}} {{^B}} {{/B}} {{/A}}',
+            '{{#A}} {{^B}} {{/B}} {{/A}} {{#C}} {{/C}}',
+        ]
+        for t in ts:
+            with self.subTest(template=t):
+                parse(t)
+
+    def test_parse_fail(self):
+        """
+        Test parsing templates in the cases there are errors.
+        """
+        ts = [
+            '{{#A}}<div> some text</div>',
+            '{{#A}}<div> some text</div>{{/A}} <div> TEXT </div> {{/B}}',
+            '{{#A}} {{#B}} {{/A}} {{/B}}',
+        ]
+        for t in ts:
+            with self.subTest(template=t):
+                with self.assertRaises(ParsingError):
+                    parse(t, raise_on_mismatch=True)