view MoinMoin/parser/text_creole.py @ 2860:60f95d2b090b

Creole parser: replaced hardcoded ../ with PARENT_PREFIX in interwiki
author Radomir Dopieralski <moindev@sheep.art.pl>
date Sun, 23 Sep 2007 23:00:01 +0200
parents 2087924a60f1
children 1c0e2cdc2d82
line wrap: on
line source
# -*- coding: iso-8859-1 -*-
"""
    MoinMoin - Creole wiki markup parser

    See http://wikicreole.org/ for latest specs.

    Notes:
    * No markup allowed in headings.
      Creole 1.0 does not require us to support this.
    * No markup allowed in table headings.
      Creole 1.0 does not require us to support this.
    * No (non-bracketed) generic url recognition: this is "mission impossible"
      except if you want to risk lots of false positives. Only known protocols
      are recognized.
    * We do not allow ":" before "//" italic markup to avoid urls with
      unrecognized schemes (like wtf://server/path) triggering italic rendering
      for the rest of the paragraph.

    @copyright: 2007 MoinMoin:RadomirDopieralski (creole 0.5 implementation),
                2007 MoinMoin:ThomasWaldmann (updates)
    @license: GNU GPL, see COPYING for details.
"""

import re
import StringIO
from MoinMoin import config, macro, wikiutil
from MoinMoin.support.python_compatibility import rsplit # Needed for python 2.3

Dependencies = []

# Whether the parser should convert \n into <br>.
bloglike_lines = False

class Parser:
    """
    Glue the DocParser and DocEmitter with the
    MoinMoin current API.
    """

    # Enable caching
    caching = 1
    Dependencies = Dependencies

    def __init__(self, raw, request, **kw):
        """Create a minimal Parser object with required attributes."""

        self.request = request
        self.form = request.form
        self.raw = raw

    def format(self, formatter):
        """Create and call the true parser and emitter."""

        document = DocParser(self.raw, self.request).parse()
        result = DocEmitter(document, formatter, self.request).emit()
        self.request.write(result)

class DocParser:
    """
    Parse the raw text and create a document object
    that can be converted into output using Emitter.
    """

    class Rules:
        """Hold all the rules and generate regular expressions."""

        # For the inline elements:
        proto = r'http|https|ftp|nntp|news|mailto|telnet|file|irc'
        url =  r'''(?P<url>
                (^ | (?<=\s | [.,:;!?()/=]))
                (?P<escaped_url>~)?
                (?P<url_target> (?P<url_proto> %s ):\S+? )
                ($ | (?=\s | [,.:;!?()] (\s | $)))
            )''' % proto
        link = r'''(?P<link>
                \[\[
                (?P<link_target>.+?) \s*
                ([|] \s* (?P<link_text>.+?) \s*)?
                ]]
            )'''
        image = r'''(?P<image>
                {{
                (?P<image_target>.+?) \s*
                ([|] \s* (?P<image_text>.+?) \s*)?
                }}
            )'''
        macro = r'''(?P<macro>
                <<
                (?P<macro_name> \w+)
                (\( (?P<macro_args> .*?) \))? \s*
                ([|] \s* (?P<macro_text> .+?) \s* )?
                >>
            )'''
        code = r'(?P<code> {{{ (?P<code_text>.*?) }}} )'
        emph = r'(?P<emph> (?<!:)// )' # there must be no : in front of the //
                                       # avoids italic rendering in urls with
                                       # unknown protocols
        strong = r'(?P<strong> \*\* )'
        linebreak = r'(?P<break> \\\\ )'
        escape = r'(?P<escape> ~ (?P<escaped_char>\S) )'
        char =  r'(?P<char> . )'

        # For the block elements:
        separator = r'(?P<rule> ^ \s* ---- \s* $ )' # horizontal line
        line = r'(?P<line> ^ \s* $ )' # empty line that separates paragraphs
        head = r'''(?P<head>
                ^ \s*
                (?P<head_head>=+) \s*
                (?P<head_text> .*? ) \s*
                (?P<head_tail>=*) \s*
                $
            )'''
        if bloglike_lines:
            text = r'(?P<text> .+ ) (?P<break> (?<!\\)$\n(?!\s*$) )?'
        else:
            text = r'(?P<text> .+ )'
        list = r'''(?P<list>
                ^ [ \t]* ([*][^*\#]|[\#][^\#*]).* $
                ( \n[ \t]* [*\#]+.* $ )*
            )''' # Matches the whole list, separate items are parsed later. The
                 # list *must* start with a single bullet.
        item = r'''(?P<item>
                ^ \s*
                (?P<item_head> [\#*]+) \s*
                (?P<item_text> .*?)
                $
            )''' # Matches single list items
        pre = r'''(?P<pre>
                ^{{{ \s* $
                (\n)?
                (?P<pre_text>
                    ([\#]!(?P<pre_kind>\w*?)(\s+.*)?$)?
                    (.|\n)+?
                )
                (\n)?
                ^}}} \s*$
            )'''
        pre_escape = r' ^(?P<indent>\s*) ~ (?P<rest> \}\}\} \s*) $'
        table = r'''(?P<table>
                ^ \s*
                [|].*? \s*
                [|]? \s*
                $
            )'''

        # For the link targets:
        extern = r'(?P<extern_addr>(?P<extern_proto>%s):.*)' % proto
        attach = r'''
                (?P<attach_scheme> attachment | inline | drawing | figure):
                (?P<attach_addr> .* )
            '''
        interwiki = r'''
                (?P<inter_wiki> [A-Z][a-zA-Z]+ ) :
                (?P<inter_page> .* )
            '''
        page = r'(?P<page_name> .* )'

        # For splitting table cells:
        cell = r'''
                \| \s*
                (
                    (?P<head> [=][^|]+ ) |
                    (?P<cell> (  %s | [^|])+ )
                ) \s*
            ''' % '|'.join([link, macro, image, code])

    # For pre escaping, in creole 1.0 done with ~:
    pre_escape_re = re.compile(Rules.pre_escape, re.M | re.X)
    link_re = re.compile('|'.join([Rules.image, Rules.linebreak, Rules.char]), re.X | re.U) # for link descriptions
    item_re = re.compile(Rules.item, re.X | re.U | re.M) # for list items
    cell_re = re.compile(Rules.cell, re.X | re.U) # for table cells
    addr_re = re.compile('|'.join([Rules.extern, Rules.attach,
        Rules.interwiki, Rules.page]), re.X | re.U) # for addresses
    # For block elements:
    block_re = re.compile('|'.join([Rules.line, Rules.head, Rules.separator,
        Rules.pre, Rules.list, Rules.table, Rules.text]), re.X | re.U | re.M)
    # For inline elements:
    inline_re = re.compile('|'.join([Rules.link, Rules.url, Rules.macro,
        Rules.code, Rules.image, Rules.strong, Rules.emph, Rules.linebreak,
        Rules.escape, Rules.char]), re.X | re.U)
    del Rules # We have the regexps compiled, rules not needed anymore

    def __init__(self, raw, request):
        self.request = request
        self.raw = raw
        self.root = DocNode('document', None)
        self.cur = self.root        # The most recent document node
        self.text = None            # The node to add inline characters to

    def _upto(self, node, kinds):
        """
        Look up the tree to the first occurence
        of one of the listed kinds of nodes or root.
        Start at the node node.
        """
        while node.parent is not None and not node.kind in kinds:
            node = node.parent
        return node

    # The _*_repl methods called for matches in regexps:

    def _url_repl(self, groups):
        """Handle raw urls in text."""
        if not groups.get('escaped_url'):
            # this url is NOT escaped
            target = groups.get('url_target', '')
            node = DocNode('external_link', self.cur)
            node.content = target
            node.proto = groups.get('url_proto', 'http')
            DocNode('text', node, node.content)
            self.text = None
        else:
            # this url is escaped, we render it as text
            if self.text is None:
                self.text = DocNode('text', self.cur, u'')
            self.text.content += groups.get('url_target')
    _url_target_repl = _url_repl
    _url_proto_repl = _url_repl

    def _link_repl(self, groups):
        """Handle all other kinds of links."""
        target = groups.get('link_target', '')
        text = (groups.get('link_text', '') or '').strip()
        parent = self.cur
        m = self.addr_re.match(target)
        if m:
            if m.group('page_name'):
                node = DocNode('page_link', self.cur)
                node.content = m.group('page_name')
            elif m.group('extern_addr'):
                node = DocNode('external_link', self.cur)
                node.content = m.group('extern_addr')
                node.proto = m.group('extern_proto')
            elif m.group('inter_wiki'):
                node = DocNode('interwiki_link', self.cur)
                node.content = '%s:%s' % (
                    m.group('inter_wiki'), m.group('inter_page'))
                if not text:
                    text = m.group('inter_page')
            elif m.group('attach_scheme'):
                scheme = m.group('attach_scheme')
                if scheme == 'inline':
                    scheme = 'inlined_attachment'
                node = DocNode(scheme, self.cur, m.group('attach_addr'))
            else:
                node = DocNode('bad_link', self.cur)
                node.content = target
            self.cur = node
            self.text = None
            re.sub(self.link_re, self._replace, text or node.content)
            self.cur = parent
        self.text = None
    _link_target_repl = _link_repl
    _link_text_repl = _link_repl

    def _macro_repl(self, groups):
        """Handles macros using the placeholder syntax."""
        name = groups.get('macro_name', '')
        text = (groups.get('macro_text', '') or '').strip()
        node = DocNode('macro', self.cur, name)
        node.args = groups.get('macro_args', '') or ''
        DocNode('text', node, text or name)
        self.text = None
    _macro_name_repl = _macro_repl
    _macro_args_repl = _macro_repl
    _macro_text_repl = _macro_repl

    def _image_repl(self, groups):
        """Handles embedded images."""
        target = groups.get('image_target', '').strip()
        text = (groups.get('image_text', '') or '').strip()
        kind = 'attachment'
        if (target.endswith('.png') or
            target.endswith('.gif') or
            target.endswith('.jpg')):
                kind = 'image'
        node = DocNode(kind, self.cur, target)
        DocNode('text', node, text or node.content)
        self.text = None
    _image_target_repl = _image_repl
    _image_text_repl = _image_repl

    def _rule_repl(self, groups):
        self.cur = self._upto(self.cur, ('document', 'section', 'blockquote'))
        DocNode('rule', self.cur)

    def _item_repl(self, groups):
        bullet = groups.get('item_head', u'')
        text = groups.get('item_text', u'')
        if bullet[-1] == '#':
            kind = 'number_list'
        else:
            kind = 'bullet_list'
        level = len(bullet)
        lst = self.cur
        # Find a list of the same kind and level up the tree
        while (lst and
                   not (lst.kind in ('number_list', 'bullet_list') and
                        lst.level == level) and
                    not lst.kind in ('document', 'section', 'blockquote')):
            lst = lst.parent
        if lst and lst.kind == kind:
            self.cur = lst
        else:
            # Create a new level of list
            self.cur = self._upto(self.cur,
                ('list_item', 'document', 'section', 'blockquote'))
            self.cur = DocNode(kind, self.cur)
            self.cur.level = level
        self.cur = DocNode('list_item', self.cur)
        self.parse_inline(text)
        self.text = None
    _item_text_repl = _item_repl
    _item_head_repl = _item_repl

    def _list_repl(self, groups):
        text = groups.get('list', u'')
        self.item_re.sub(self._replace, text)

    def _head_repl(self, groups):
        self.cur = self._upto(self.cur, ('document', 'section', 'blockquote'))
        node = DocNode('header', self.cur, groups.get('head_text', '').strip())
        node.level = len(groups.get('head_head', ' '))
    _head_head_repl = _head_repl
    _head_text_repl = _head_repl

    def _text_repl(self, groups):
        if self.cur.kind in ('table', 'table_row', 'bullet_list',
            'number_list'):
            self.cur = self._upto(self.cur,
                ('document', 'section', 'blockquote'))
        if self.cur.kind in ('document', 'section', 'blockquote'):
            self.cur = DocNode('paragraph', self.cur)
        self.parse_inline(groups.get('text', '')+' ')
        if groups.get('break') and self.cur.kind in ('paragraph',
            'emphasis', 'strong', 'code'):
            DocNode('break', self.cur, '')
        self.text = None
    _break_repl = _text_repl

    def _table_repl(self, groups):
        row = groups.get('table', '|').strip()
        self.cur = self._upto(self.cur, (
            'table', 'document', 'section', 'blockquote'))
        if self.cur.kind != 'table':
            self.cur = DocNode('table', self.cur)
        tb = self.cur
        tr = DocNode('table_row', tb)

        text = ''
        for m in self.cell_re.finditer(row):
            cell = m.group('cell')
            if cell:
                self.cur = DocNode('table_cell', tr)
                self.text = None
                self.parse_inline(cell)
            else:
                cell = m.group('head')
                self.cur = DocNode('table_head', tr)
                self.text = DocNode('text', self.cur, u'')
                self.text.content = cell.strip('=')
        self.cur = tb
        self.text = None

    def _pre_repl(self, groups):
        self.cur = self._upto(self.cur, ('document', 'section', 'blockquote'))
        kind = groups.get('pre_kind', None)
        text = groups.get('pre_text', u'')
        def remove_tilde(m):
            return m.group('indent') + m.group('rest')
        text = self.pre_escape_re.sub(remove_tilde, text)
        node = DocNode('preformatted', self.cur, text)
        node.sect = kind or ''
        self.text = None
    _pre_text_repl = _pre_repl
    _pre_head_repl = _pre_repl
    _pre_kind_repl = _pre_repl

    def _line_repl(self, groups):
        self.cur = self._upto(self.cur, ('document', 'section', 'blockquote'))

    def _code_repl(self, groups):
        DocNode('code', self.cur, groups.get('code_text', u'').strip())
        self.text = None
    _code_text_repl = _code_repl
    _code_head_repl = _code_repl

    def _emph_repl(self, groups):
        if self.cur.kind != 'emphasis':
            self.cur = DocNode('emphasis', self.cur)
        else:
            self.cur = self._upto(self.cur, ('emphasis', )).parent
        self.text = None

    def _strong_repl(self, groups):
        if self.cur.kind != 'strong':
            self.cur = DocNode('strong', self.cur)
        else:
            self.cur = self._upto(self.cur, ('strong', )).parent
        self.text = None

    def _break_repl(self, groups):
        DocNode('break', self.cur, None)
        self.text = None

    def _escape_repl(self, groups):
        if self.text is None:
            self.text = DocNode('text', self.cur, u'')
        self.text.content += groups.get('escaped_char', u'')

    def _char_repl(self, groups):
        if self.text is None:
            self.text = DocNode('text', self.cur, u'')
        self.text.content += groups.get('char', u'')

    def _replace(self, match):
        """Invoke appropriate _*_repl method. Called for every matched group."""

        groups = match.groupdict()
        for name, text in groups.iteritems():
            if text is not None:
                replace = getattr(self, '_%s_repl' % name)
                replace(groups)
                return

    def parse_inline(self, raw):
        """Recognize inline elements inside blocks."""

        re.sub(self.inline_re, self._replace, raw)

    def parse_block(self, raw):
        """Recognize block elements."""

        re.sub(self.block_re, self._replace, raw)

    def parse(self):
        self.parse_block(self.raw)
        return self.root

#################### Helper classes

### The document model and emitter follow

class DocNode:
    """
    A node in the document.
    """

    def __init__(self, kind='', parent=None, content=None):
        self.children = []
        self.parent = parent
        self.kind = kind
        self.content = content
        if not self.parent is None:
            self.parent.children.append(self)


class DocEmitter:
    """
    Generate the output for the document
    tree consisting of DocNodes.
    """

    def __init__(self, root, formatter, request):
        self.root = root
        self.formatter = formatter
        self.request = request
        self.form = request.form
        self.macro = None

    def get_image(self, addr, text=''):
        """Return markup for image depending on the address."""

        if addr is None:
            addr = ''
        url = wikiutil.url_unquote(addr, want_unicode=True)
        if addr.startswith('http:'):
            return self.formatter.image(
                src=url, alt=text, html_class='external_image'
            )
        else:
            return self.formatter.attachment_image(
                url, alt=text, html_class='image'
            )

    def get_text(self, node):
        """Try to emit whatever text is in the node."""

        try:
            return node.children[0].content or ''
        except:
            return node.content or ''

    # *_emit methods for emitting nodes of the document:

    def document_emit(self, node):
        return self.emit_children(node)

    def text_emit(self, node):
        return self.formatter.text(node.content or '')

    def rule_emit(self, node):
        return self.formatter.rule()

    def paragraph_emit(self, node):
        return ''.join([
            self.formatter.paragraph(1),
            self.emit_children(node),
            self.formatter.paragraph(0),
        ])

    def bullet_list_emit(self, node):
        return ''.join([
            self.formatter.bullet_list(1),
            self.emit_children(node),
            self.formatter.bullet_list(0),
        ])

    def number_list_emit(self, node):
        return ''.join([
            self.formatter.number_list(1),
            self.emit_children(node),
            self.formatter.number_list(0),
        ])

    def list_item_emit(self, node):
        return ''.join([
            self.formatter.listitem(1),
            self.emit_children(node),
            self.formatter.listitem(0),
        ])

    def definition_list_emit(self, node):
        return ''.join([
            self.formatter.definition_list(1),
            self.emit_children(node),
            self.formatter.definition_list(0),
        ])

    def term_emit(self, node):
        return ''.join([
            self.formatter.definition_term(1),
            self.emit_children(node),
            self.formatter.definition_term(0),
        ])

    def definition_emit(self, node):
        return ''.join([
            self.formatter.definition_desc(1),
            self.emit_children(node),
            self.formatter.definition_desc(0),
        ])

    def table_emit(self, node):
        return ''.join([
            self.formatter.table(1, attrs=getattr(node, 'attrs', '')),
            self.emit_children(node),
            self.formatter.table(0),
        ])

    def table_row_emit(self, node):
        return ''.join([
            self.formatter.table_row(1, attrs=getattr(node, 'attrs', '')),
            self.emit_children(node),
            self.formatter.table_row(0),
        ])

    def table_cell_emit(self, node):
        return ''.join([
            self.formatter.table_cell(1, attrs=getattr(node, 'attrs', '')),
            self.emit_children(node),
            self.formatter.table_cell(0),
        ])

    def table_head_emit(self, node):
        return ''.join([
            self.formatter.rawHTML('<th>'),
            self.emit_children(node),
            self.formatter.rawHTML('</th>'),
        ])

    def emphasis_emit(self, node):
        return ''.join([
            self.formatter.emphasis(1),
            self.emit_children(node),
            self.formatter.emphasis(0),
        ])

    def quote_emit(self, node):
        return ''.join([
            self.formatter.rawHTML('<q>'),
            self.emit_children(node),
            self.formatter.rawHTML('</q>'),
        ])

    def strong_emit(self, node):
        return ''.join([
            self.formatter.strong(1),
            self.emit_children(node),
            self.formatter.strong(0),
        ])

    def smiley_emit(self, node):
        return self.formatter.smiley(node.content)

    def header_emit(self, node):
        import sha
        pntt = '%s%s%d' % (self.formatter.page.page_name,
            self.get_text(node), node.level)
        ident = "head-%s" % sha.new(pntt.encode(config.charset)).hexdigest()
        return ''.join([
            self.formatter.heading(1, node.level, id=ident),
            self.formatter.text(node.content or ''),
            self.formatter.heading(0, node.level),
        ])

    def code_emit(self, node):
# XXX The current formatter will replace all spaces with &nbsp;, so we need
# to use rawHTML instead, until that is fixed.
#        return ''.join([
#            self.formatter.code(1),
#            self.formatter.text(node.content or ''),
#            self.formatter.code(0),
#        ])
        return ''.join([
            self.formatter.rawHTML('<tt>'),
            self.formatter.text(node.content or ''),
            self.formatter.rawHTML('</tt>'),
        ])

    def abbr_emit(self, node):
        return ''.join([
            self.formatter.rawHTML('<abbr title="%s">' % node.title),
            self.formatter.text(node.content or ''),
            self.formatter.rawHTML('</abbr>'),
        ])

    def page_link_emit(self, node):
        word = node.content
        # handle relative links
        if word.startswith(wikiutil.PARENT_PREFIX):
            word = word[wikiutil.PARENT_PREFIX_LEN:]
        elif word.startswith(wikiutil.CHILD_PREFIX):
            word = "%s/%s" % (self.formatter.page.page_name,
                word[wikiutil.CHILD_PREFIX_LEN:])
        # handle anchors
        parts = rsplit(word, "#", 1)
        anchor = ""
        if len(parts) == 2:
            word, anchor = parts
        return ''.join([
            self.formatter.pagelink(1, word, anchor=anchor),
            self.emit_children(node),
            self.formatter.pagelink(0, word),
        ])

    def external_link_emit(self, node):
        return ''.join([
            self.formatter.url(1, node.content, css=node.proto),
            self.emit_children(node),
            self.formatter.url(0),
        ])

    def anchor_link_emit(self, node):
        return ''.join([
            self.formatter.url(1, node.content, css='anchor'),
            self.emit_children(node),
            self.formatter.url(0),
        ])

    def interwiki_link_emit(self, node):
        wiki, page = wikiutil.split_interwiki(node.content)
        wikitag, wikiurl, wikitail, wikitag_bad = \
            wikiutil.resolve_interwiki(self.request, wiki, page)
        href = wikiutil.join_wiki(wikiurl, wikitail)
        return ''.join([
            self.formatter.interwikilink(1, wikitag, wikitail, title=wikitag),
            self.emit_children(node),
            self.formatter.interwikilink(0),
        ])

    def attachment_emit(self, node):
        url = wikiutil.url_unquote(node.content, want_unicode=True)
        text = self.get_text(node)
        return (self.formatter.attachment_link(1, url) +
                self.formatter.text(text) +
                self.formatter.attachment_link(0))

    def inlined_attachment_emit(self, node):
        url = wikiutil.url_unquote(node.content, want_unicode=True)
        text = self.get_text(node)
        return self.formatter.attachment_inlined(url, text)

    def image_emit(self, node):
        text = self.get_text(node)
        return self.get_image(node.content, text)

    def drawing_emit(self, node):
        url = wikiutil.url_unquote(node.content, want_unicode=True)
        text = self.get_text(node)
        return self.formatter.attachment_drawing(url, text)

    def figure_emit(self, node):
        text = self.get_text(node)
        url = wikiutil.url_unquote(node.content, want_unicode=True)
        return ''.join([
            self.formatter.rawHTML('<div class="figure">'),
            self.get_image(url, text), self.emit_children(node),
            self.formatter.rawHTML('</div>'),
        ])

    def bad_link_emit(self, node):
        return self.formatter.text(''.join([
            '[[',
            node.content or '',
            ']]',
        ]))

    def macro_emit(self, node):
        macro_name = node.content
        args = node.args
        if self.macro is None:
            self.macro = macro.Macro(self)
        try:
            return self.formatter.macro(self.macro, macro_name, args)
        except:
            return self.formatter.text(self.request.getText('macro error'))

    def section_emit(self, node):
        return ''.join([
            self.formatter.rawHTML(
                '<div class="%s" style="%s">' % (node.sect, node.style)),
            self.emit_children(node),
            self.formatter.rawHTML('</div>'),
        ])

    def break_emit(self, node):
        return ''.join([
            self.formatter.rawHTML('<br>'),
        ])

    def blockquote_emit(self, node):
        return ''.join([
            self.formatter.rawHTML('<blockquote>'),
            self.emit_children(node),
            self.formatter.rawHTML('</blockquote>'),
        ])

    def preformatted_emit(self, node):
        content = node.content
        self.parser = None
        parser_name = getattr(node, 'sect', '')
        if parser_name:
            self.setParser(parser_name)
        if self.parser is None:
            self.parser_name = None
            return ''.join([
                self.formatter.preformatted(1),
                self.formatter.text(content),
                self.formatter.preformatted(0),
            ])
        else:
            self.parser_name = parser_name
            return self.request.redirectedOutput(
                self.formatter.parser, self.parser_name, content.split('\n'))

    def default_emit(self, node):
        return ''.join([
            self.formatter.preformatted(1),
            self.formatter.text('<%s>\n' % node.kind),
            self.emit_children(node),
            self.formatter.preformatted(0),
        ])

    def emit_children(self, node):
        """Emit all the children of a node."""
        return ''.join([self.emit_node(child) for child in node.children])

    def emit_node(self, node):
        try:
            emit = getattr(self, '%s_emit' % node.kind)
        except:
            emit = self.default_emit
        return emit(node)

    def emit(self):
        # Try to disable 'smart' formatting if possible
        magic_save = getattr(self.formatter, 'no_magic', False)
        self.formatter.no_magic = True
        output = '\n'.join([
            self.emit_node(self.root),
        ])
        self.formatter.no_magic = magic_save
        return output


# Private helpers ------------------------------------------------------------

    def setParser(self, name):
        """ Set parser to parser named 'name' """
        # XXX this is done by the formatter as well
        try:
            self.parser = wikiutil.searchAndImportPlugin(self.request.cfg,
                "parser", name)
        except wikiutil.PluginMissingError:
            self.parser = None