Adding pystache to third_party

third_party/pystache/src/parser.py

+# coding: utf-8
+
+"""
+Exposes a parse() function to parse template strings.
+
+"""
+
+import re
+
+from pystache import defaults
+from pystache.parsed import ParsedTemplate
+
+
+END_OF_LINE_CHARACTERS = [u'\r', u'\n']
+NON_BLANK_RE = re.compile(ur'^(.)', re.M)
+
+
+# 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):
+    """
+    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.
+
+    Examples:
+
+    >>> parsed = parse(u"Hey {{#who}}{{name}}!{{/who}}")
+    >>> print str(parsed).replace('u', '')  # This is a hack to get the test to pass both in Python 2 and 3.
+    ['Hey ', _SectionNode(key='who', index_begin=12, index_end=21, parsed=[_EscapeNode(key='name'), '!'])]
+
+    """
+    if type(template) is not unicode:
+        raise Exception("Template is not unicode: %s" % type(template))
+    parser = _Parser(delimiters)
+    return parser.parse(template)
+
+
+def _compile_template_re(delimiters):
+    """
+    Return a regular expression object (re.RegexObject) instance.
+
+    """
+    # The possible tag type characters following the opening tag,
+    # excluding "=" and "{".
+    tag_types = "!>&/#^"
+
+    # TODO: are we following this in the spec?
+    #
+    #   The tag's content MUST be a non-whitespace character sequence
+    #   NOT containing the current closing delimiter.
+    #
+    tag = r"""
+        (?P<whitespace>[\ \t]*)
+        %(otag)s \s*
+        (?:
+          (?P<change>=) \s* (?P<delims>.+?)   \s* = |
+          (?P<raw>{)    \s* (?P<raw_name>.+?) \s* } |
+          (?P<tag>[%(tag_types)s]?)  \s* (?P<tag_key>[\s\S]+?)
+        )
+        \s* %(ctag)s
+    """ % {'tag_types': tag_types, 'otag': re.escape(delimiters[0]), 'ctag': re.escape(delimiters[1])}
+
+    return re.compile(tag, re.VERBOSE)
+
+
+class ParsingError(Exception):
+
+    pass
+
+
+## Node types
+
+def _format(obj, exclude=None):
+    if exclude is None:
+        exclude = []
+    exclude.append('key')
+    attrs = obj.__dict__
+    names = list(set(attrs.keys()) - set(exclude))
+    names.sort()
+    names.insert(0, 'key')
+    args = ["%s=%s" % (name, repr(attrs[name])) for name in names]
+    return "%s(%s)" % (obj.__class__.__name__, ", ".join(args))
+
+
+class _CommentNode(object):
+
+    def __repr__(self):
+        return _format(self)
+
+    def render(self, engine, context):
+        return u''
+
+
+class _ChangeNode(object):
+
+    def __init__(self, delimiters):
+        self.delimiters = delimiters
+
+    def __repr__(self):
+        return _format(self)
+
+    def render(self, engine, context):
+        return u''
+
+
+class _EscapeNode(object):
+
+    def __init__(self, key):
+        self.key = key
+
+    def __repr__(self):
+        return _format(self)
+
+    def render(self, engine, context):
+        s = engine.fetch_string(context, self.key)
+        return engine.escape(s)
+
+
+class _LiteralNode(object):
+
+    def __init__(self, key):
+        self.key = key
+
+    def __repr__(self):
+        return _format(self)
+
+    def render(self, engine, context):
+        s = engine.fetch_string(context, self.key)
+        return engine.literal(s)
+
+
+class _PartialNode(object):
+
+    def __init__(self, key, indent):
+        self.key = key
+        self.indent = indent
+
+    def __repr__(self):
+        return _format(self)
+
+    def render(self, engine, context):
+        template = engine.resolve_partial(self.key)
+        # Indent before rendering.
+        template = re.sub(NON_BLANK_RE, self.indent + ur'\1', template)
+
+        return engine.render(template, context)
+
+
+class _InvertedNode(object):
+
+    def __init__(self, key, parsed_section):
+        self.key = key
+        self.parsed_section = parsed_section
+
+    def __repr__(self):
+        return _format(self)
+
+    def render(self, engine, context):
+        # TODO: is there a bug because we are not using the same
+        #   logic as in fetch_string()?
+        data = engine.resolve_context(context, self.key)
+        # Note that lambdas are considered truthy for inverted sections
+        # per the spec.
+        if data:
+            return u''
+        return self.parsed_section.render(engine, context)
+
+
+class _SectionNode(object):
+
+    # TODO: the template_ and parsed_template_ arguments don't both seem
+    # to be necessary.  Can we remove one of them?  For example, if
+    # callable(data) is True, then the initial parsed_template isn't used.
+    def __init__(self, key, parsed, delimiters, template, index_begin, index_end):
+        self.delimiters = delimiters
+        self.key = key
+        self.parsed = parsed
+        self.template = template
+        self.index_begin = index_begin
+        self.index_end = index_end
+
+    def __repr__(self):
+        return _format(self, exclude=['delimiters', 'template'])
+
+    def render(self, engine, context):
+        values = engine.fetch_section_data(context, self.key)
+
+        parts = []
+        for val in values:
+            if callable(val):
+                # Lambdas special case section rendering and bypass pushing
+                # the data value onto the context stack.  From the spec--
+                #
+                #   When used as the data value for a Section tag, the
+                #   lambda MUST be treatable as an arity 1 function, and
+                #   invoked as such (passing a String containing the
+                #   unprocessed section contents).  The returned value
+                #   MUST be rendered against the current delimiters, then
+                #   interpolated in place of the section.
+                #
+                #  Also see--
+                #
+                #   https://github.com/defunkt/pystache/issues/113
+                #
+                # TODO: should we check the arity?
+                val = val(self.template[self.index_begin:self.index_end])
+                val = engine._render_value(val, context, delimiters=self.delimiters)
+                parts.append(val)
+                continue
+
+            context.push(val)
+            parts.append(self.parsed.render(engine, context))
+            context.pop()
+
+        return unicode(''.join(parts))
+
+
+class _Parser(object):
+
+    _delimiters = None
+    _template_re = None
+
+    def __init__(self, delimiters=None):
+        if delimiters is None:
+            delimiters = defaults.DELIMITERS
+
+        self._delimiters = delimiters
+
+    def _compile_delimiters(self):
+        self._template_re = _compile_template_re(self._delimiters)
+
+    def _change_delimiters(self, delimiters):
+        self._delimiters = delimiters
+        self._compile_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.
+
+        """
+        self._compile_delimiters()
+
+        start_index = 0
+        content_end_index, parsed_section, section_key = None, None, None
+        parsed_template = ParsedTemplate()
+
+        states = []
+
+        while True:
+            match = self._template_re.search(template, start_index)
+
+            if match is None:
+                break
+
+            match_index = match.start()
+            end_index = match.end()
+
+            matches = match.groupdict()
+
+            # Normalize the matches dictionary.
+            if matches['change'] is not None:
+                matches.update(tag='=', tag_key=matches['delims'])
+            elif matches['raw'] is not None:
+                matches.update(tag='&', tag_key=matches['raw_name'])
+
+            tag_type = matches['tag']
+            tag_key = matches['tag_key']
+            leading_whitespace = matches['whitespace']
+
+            # Standalone (non-interpolation) tags consume the entire line,
+            # both leading whitespace and trailing newline.
+            did_tag_begin_line = match_index == 0 or template[match_index - 1] in END_OF_LINE_CHARACTERS
+            did_tag_end_line = end_index == len(template) or template[end_index] in END_OF_LINE_CHARACTERS
+            is_tag_interpolating = tag_type in ['', '&']
+
+            if did_tag_begin_line and did_tag_end_line and not is_tag_interpolating:
+                if end_index < len(template):
+                    end_index += template[end_index] == '\r' and 1 or 0
+                if end_index < len(template):
+                    end_index += template[end_index] == '\n' and 1 or 0
+            elif leading_whitespace:
+                match_index += len(leading_whitespace)
+                leading_whitespace = ''
+
+            # Avoid adding spurious empty strings to the parse tree.
+            if start_index != match_index:
+                parsed_template.add(template[start_index:match_index])
+
+            start_index = end_index
+
+            if tag_type in ('#', '^'):
+                # Cache current state.
+                state = (tag_type, end_index, section_key, parsed_template)
+                states.append(state)
+
+                # Initialize new state
+                section_key, parsed_template = tag_key, ParsedTemplate()
+                continue
+
+            if tag_type == '/':
+                if tag_key != section_key:
+                    raise ParsingError("Section end tag mismatch: %s != %s" % (tag_key, section_key))
+
+                # Restore previous state with newly found section data.
+                parsed_section = parsed_template
+
+                (tag_type, section_start_index, section_key, parsed_template) = states.pop()
+                node = self._make_section_node(template, tag_type, tag_key, parsed_section,
+                                               section_start_index, match_index)
+
+            else:
+                node = self._make_interpolation_node(tag_type, tag_key, leading_whitespace)
+
+            parsed_template.add(node)
+
+        # Avoid adding spurious empty strings to the parse tree.
+        if start_index != len(template):
+            parsed_template.add(template[start_index:])
+
+        return parsed_template
+
+    def _make_interpolation_node(self, tag_type, tag_key, leading_whitespace):
+        """
+        Create and return a non-section node for the parse tree.
+
+        """
+        # TODO: switch to using a dictionary instead of a bunch of ifs and elifs.
+        if tag_type == '!':
+            return _CommentNode()
+
+        if tag_type == '=':
+            delimiters = tag_key.split()
+            self._change_delimiters(delimiters)
+            return _ChangeNode(delimiters)
+
+        if tag_type == '':
+            return _EscapeNode(tag_key)
+
+        if tag_type == '&':
+            return _LiteralNode(tag_key)
+
+        if tag_type == '>':
+            return _PartialNode(tag_key, leading_whitespace)
+
+        raise Exception("Invalid symbol for interpolation tag: %s" % repr(tag_type))
+
+    def _make_section_node(self, template, tag_type, tag_key, parsed_section,
+                           section_start_index, section_end_index):
+        """
+        Create and return a section node for the parse tree.
+
+        """
+        if tag_type == '#':
+            return _SectionNode(tag_key, parsed_section, self._delimiters,
+                               template, section_start_index, section_end_index)
+
+        if tag_type == '^':
+            return _InvertedNode(tag_key, parsed_section)
+
+        raise Exception("Invalid symbol for section tag: %s" % repr(tag_type))