573 lines
22 KiB
Python
573 lines
22 KiB
Python
"""
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CORE MARKDOWN BLOCKPARSER
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===========================================================================
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This parser handles basic parsing of Markdown blocks. It doesn't concern
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itself with inline elements such as **bold** or *italics*, but rather just
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catches blocks, lists, quotes, etc.
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The BlockParser is made up of a bunch of BlockProssors, each handling a
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different type of block. Extensions may add/replace/remove BlockProcessors
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as they need to alter how markdown blocks are parsed.
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"""
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from __future__ import absolute_import
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from __future__ import division
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from __future__ import unicode_literals
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import logging
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import re
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from . import util
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from .blockparser import BlockParser
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logger = logging.getLogger('MARKDOWN')
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def build_block_parser(md_instance, **kwargs):
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""" Build the default block parser used by Markdown. """
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parser = BlockParser(md_instance)
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parser.blockprocessors['empty'] = EmptyBlockProcessor(parser)
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parser.blockprocessors['indent'] = ListIndentProcessor(parser)
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parser.blockprocessors['code'] = CodeBlockProcessor(parser)
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parser.blockprocessors['hashheader'] = HashHeaderProcessor(parser)
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parser.blockprocessors['setextheader'] = SetextHeaderProcessor(parser)
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parser.blockprocessors['hr'] = HRProcessor(parser)
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parser.blockprocessors['olist'] = OListProcessor(parser)
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parser.blockprocessors['ulist'] = UListProcessor(parser)
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parser.blockprocessors['quote'] = BlockQuoteProcessor(parser)
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parser.blockprocessors['paragraph'] = ParagraphProcessor(parser)
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return parser
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class BlockProcessor(object):
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""" Base class for block processors.
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Each subclass will provide the methods below to work with the source and
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tree. Each processor will need to define it's own ``test`` and ``run``
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methods. The ``test`` method should return True or False, to indicate
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whether the current block should be processed by this processor. If the
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test passes, the parser will call the processors ``run`` method.
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"""
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def __init__(self, parser):
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self.parser = parser
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self.tab_length = parser.markdown.tab_length
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def lastChild(self, parent):
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""" Return the last child of an etree element. """
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if len(parent):
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return parent[-1]
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else:
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return None
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def detab(self, text):
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""" Remove a tab from the front of each line of the given text. """
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newtext = []
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lines = text.split('\n')
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for line in lines:
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if line.startswith(' '*self.tab_length):
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newtext.append(line[self.tab_length:])
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elif not line.strip():
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newtext.append('')
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else:
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break
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return '\n'.join(newtext), '\n'.join(lines[len(newtext):])
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def looseDetab(self, text, level=1):
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""" Remove a tab from front of lines but allowing dedented lines. """
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lines = text.split('\n')
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for i in range(len(lines)):
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if lines[i].startswith(' '*self.tab_length*level):
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lines[i] = lines[i][self.tab_length*level:]
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return '\n'.join(lines)
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def test(self, parent, block):
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""" Test for block type. Must be overridden by subclasses.
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As the parser loops through processors, it will call the ``test``
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method on each to determine if the given block of text is of that
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type. This method must return a boolean ``True`` or ``False``. The
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actual method of testing is left to the needs of that particular
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block type. It could be as simple as ``block.startswith(some_string)``
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or a complex regular expression. As the block type may be different
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depending on the parent of the block (i.e. inside a list), the parent
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etree element is also provided and may be used as part of the test.
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Keywords:
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* ``parent``: A etree element which will be the parent of the block.
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* ``block``: A block of text from the source which has been split at
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blank lines.
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"""
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pass # pragma: no cover
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def run(self, parent, blocks):
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""" Run processor. Must be overridden by subclasses.
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When the parser determines the appropriate type of a block, the parser
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will call the corresponding processor's ``run`` method. This method
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should parse the individual lines of the block and append them to
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the etree.
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Note that both the ``parent`` and ``etree`` keywords are pointers
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to instances of the objects which should be edited in place. Each
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processor must make changes to the existing objects as there is no
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mechanism to return new/different objects to replace them.
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This means that this method should be adding SubElements or adding text
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to the parent, and should remove (``pop``) or add (``insert``) items to
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the list of blocks.
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Keywords:
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* ``parent``: A etree element which is the parent of the current block.
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* ``blocks``: A list of all remaining blocks of the document.
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"""
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pass # pragma: no cover
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class ListIndentProcessor(BlockProcessor):
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""" Process children of list items.
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Example:
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* a list item
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process this part
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or this part
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"""
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ITEM_TYPES = ['li']
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LIST_TYPES = ['ul', 'ol']
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def __init__(self, *args):
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super(ListIndentProcessor, self).__init__(*args)
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self.INDENT_RE = re.compile(r'^(([ ]{%s})+)' % self.tab_length)
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def test(self, parent, block):
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return block.startswith(' '*self.tab_length) and \
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not self.parser.state.isstate('detabbed') and \
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(parent.tag in self.ITEM_TYPES or
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(len(parent) and parent[-1] is not None and
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(parent[-1].tag in self.LIST_TYPES)))
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def run(self, parent, blocks):
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block = blocks.pop(0)
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level, sibling = self.get_level(parent, block)
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block = self.looseDetab(block, level)
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self.parser.state.set('detabbed')
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if parent.tag in self.ITEM_TYPES:
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# It's possible that this parent has a 'ul' or 'ol' child list
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# with a member. If that is the case, then that should be the
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# parent. This is intended to catch the edge case of an indented
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# list whose first member was parsed previous to this point
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# see OListProcessor
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if len(parent) and parent[-1].tag in self.LIST_TYPES:
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self.parser.parseBlocks(parent[-1], [block])
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else:
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# The parent is already a li. Just parse the child block.
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self.parser.parseBlocks(parent, [block])
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elif sibling.tag in self.ITEM_TYPES:
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# The sibling is a li. Use it as parent.
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self.parser.parseBlocks(sibling, [block])
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elif len(sibling) and sibling[-1].tag in self.ITEM_TYPES:
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# The parent is a list (``ol`` or ``ul``) which has children.
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# Assume the last child li is the parent of this block.
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if sibling[-1].text:
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# If the parent li has text, that text needs to be moved to a p
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# The p must be 'inserted' at beginning of list in the event
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# that other children already exist i.e.; a nested sublist.
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p = util.etree.Element('p')
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p.text = sibling[-1].text
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sibling[-1].text = ''
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sibling[-1].insert(0, p)
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self.parser.parseChunk(sibling[-1], block)
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else:
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self.create_item(sibling, block)
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self.parser.state.reset()
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def create_item(self, parent, block):
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""" Create a new li and parse the block with it as the parent. """
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li = util.etree.SubElement(parent, 'li')
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self.parser.parseBlocks(li, [block])
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def get_level(self, parent, block):
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""" Get level of indent based on list level. """
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# Get indent level
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m = self.INDENT_RE.match(block)
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if m:
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indent_level = len(m.group(1))/self.tab_length
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else:
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indent_level = 0
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if self.parser.state.isstate('list'):
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# We're in a tightlist - so we already are at correct parent.
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level = 1
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else:
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# We're in a looselist - so we need to find parent.
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level = 0
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# Step through children of tree to find matching indent level.
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while indent_level > level:
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child = self.lastChild(parent)
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if (child is not None and
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(child.tag in self.LIST_TYPES or child.tag in self.ITEM_TYPES)):
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if child.tag in self.LIST_TYPES:
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level += 1
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parent = child
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else:
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# No more child levels. If we're short of indent_level,
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# we have a code block. So we stop here.
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break
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return level, parent
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class CodeBlockProcessor(BlockProcessor):
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""" Process code blocks. """
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def test(self, parent, block):
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return block.startswith(' '*self.tab_length)
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def run(self, parent, blocks):
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sibling = self.lastChild(parent)
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block = blocks.pop(0)
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theRest = ''
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if (sibling is not None and sibling.tag == "pre" and
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len(sibling) and sibling[0].tag == "code"):
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# The previous block was a code block. As blank lines do not start
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# new code blocks, append this block to the previous, adding back
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# linebreaks removed from the split into a list.
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code = sibling[0]
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block, theRest = self.detab(block)
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code.text = util.AtomicString(
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'%s\n%s\n' % (code.text, block.rstrip())
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)
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else:
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# This is a new codeblock. Create the elements and insert text.
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pre = util.etree.SubElement(parent, 'pre')
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code = util.etree.SubElement(pre, 'code')
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block, theRest = self.detab(block)
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code.text = util.AtomicString('%s\n' % block.rstrip())
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if theRest:
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# This block contained unindented line(s) after the first indented
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# line. Insert these lines as the first block of the master blocks
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# list for future processing.
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blocks.insert(0, theRest)
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class BlockQuoteProcessor(BlockProcessor):
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RE = re.compile(r'(^|\n)[ ]{0,3}>[ ]?(.*)')
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def test(self, parent, block):
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return bool(self.RE.search(block))
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def run(self, parent, blocks):
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block = blocks.pop(0)
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m = self.RE.search(block)
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if m:
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before = block[:m.start()] # Lines before blockquote
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# Pass lines before blockquote in recursively for parsing forst.
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self.parser.parseBlocks(parent, [before])
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# Remove ``> `` from begining of each line.
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block = '\n'.join(
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[self.clean(line) for line in block[m.start():].split('\n')]
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)
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sibling = self.lastChild(parent)
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if sibling is not None and sibling.tag == "blockquote":
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# Previous block was a blockquote so set that as this blocks parent
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quote = sibling
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else:
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# This is a new blockquote. Create a new parent element.
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quote = util.etree.SubElement(parent, 'blockquote')
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# Recursively parse block with blockquote as parent.
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# change parser state so blockquotes embedded in lists use p tags
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self.parser.state.set('blockquote')
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self.parser.parseChunk(quote, block)
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self.parser.state.reset()
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def clean(self, line):
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""" Remove ``>`` from beginning of a line. """
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m = self.RE.match(line)
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if line.strip() == ">":
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return ""
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elif m:
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return m.group(2)
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else:
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return line
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class OListProcessor(BlockProcessor):
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""" Process ordered list blocks. """
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TAG = 'ol'
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# The integer (python string) with which the lists starts (default=1)
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# Eg: If list is intialized as)
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# 3. Item
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# The ol tag will get starts="3" attribute
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STARTSWITH = '1'
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# List of allowed sibling tags.
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SIBLING_TAGS = ['ol', 'ul']
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def __init__(self, parser):
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super(OListProcessor, self).__init__(parser)
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# Detect an item (``1. item``). ``group(1)`` contains contents of item.
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self.RE = re.compile(r'^[ ]{0,%d}\d+\.[ ]+(.*)' % (self.tab_length - 1))
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# Detect items on secondary lines. they can be of either list type.
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self.CHILD_RE = re.compile(r'^[ ]{0,%d}((\d+\.)|[*+-])[ ]+(.*)' %
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(self.tab_length - 1))
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# Detect indented (nested) items of either type
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self.INDENT_RE = re.compile(r'^[ ]{%d,%d}((\d+\.)|[*+-])[ ]+.*' %
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(self.tab_length, self.tab_length * 2 - 1))
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def test(self, parent, block):
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return bool(self.RE.match(block))
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def run(self, parent, blocks):
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# Check fr multiple items in one block.
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items = self.get_items(blocks.pop(0))
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sibling = self.lastChild(parent)
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if sibling is not None and sibling.tag in self.SIBLING_TAGS:
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# Previous block was a list item, so set that as parent
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lst = sibling
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# make sure previous item is in a p- if the item has text,
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# then it isn't in a p
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if lst[-1].text:
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# since it's possible there are other children for this
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# sibling, we can't just SubElement the p, we need to
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# insert it as the first item.
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p = util.etree.Element('p')
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p.text = lst[-1].text
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lst[-1].text = ''
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lst[-1].insert(0, p)
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# if the last item has a tail, then the tail needs to be put in a p
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# likely only when a header is not followed by a blank line
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lch = self.lastChild(lst[-1])
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if lch is not None and lch.tail:
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p = util.etree.SubElement(lst[-1], 'p')
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p.text = lch.tail.lstrip()
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lch.tail = ''
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# parse first block differently as it gets wrapped in a p.
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li = util.etree.SubElement(lst, 'li')
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self.parser.state.set('looselist')
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firstitem = items.pop(0)
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self.parser.parseBlocks(li, [firstitem])
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self.parser.state.reset()
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elif parent.tag in ['ol', 'ul']:
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# this catches the edge case of a multi-item indented list whose
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# first item is in a blank parent-list item:
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# * * subitem1
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# * subitem2
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# see also ListIndentProcessor
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lst = parent
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else:
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# This is a new list so create parent with appropriate tag.
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lst = util.etree.SubElement(parent, self.TAG)
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# Check if a custom start integer is set
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if not self.parser.markdown.lazy_ol and self.STARTSWITH != '1':
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lst.attrib['start'] = self.STARTSWITH
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self.parser.state.set('list')
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# Loop through items in block, recursively parsing each with the
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# appropriate parent.
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for item in items:
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if item.startswith(' '*self.tab_length):
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# Item is indented. Parse with last item as parent
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self.parser.parseBlocks(lst[-1], [item])
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else:
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# New item. Create li and parse with it as parent
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li = util.etree.SubElement(lst, 'li')
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self.parser.parseBlocks(li, [item])
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self.parser.state.reset()
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def get_items(self, block):
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""" Break a block into list items. """
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items = []
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for line in block.split('\n'):
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m = self.CHILD_RE.match(line)
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if m:
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# This is a new list item
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# Check first item for the start index
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if not items and self.TAG == 'ol':
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# Detect the integer value of first list item
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INTEGER_RE = re.compile(r'(\d+)')
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self.STARTSWITH = INTEGER_RE.match(m.group(1)).group()
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# Append to the list
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items.append(m.group(3))
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elif self.INDENT_RE.match(line):
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# This is an indented (possibly nested) item.
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if items[-1].startswith(' '*self.tab_length):
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# Previous item was indented. Append to that item.
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items[-1] = '%s\n%s' % (items[-1], line)
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else:
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items.append(line)
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else:
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# This is another line of previous item. Append to that item.
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items[-1] = '%s\n%s' % (items[-1], line)
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return items
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class UListProcessor(OListProcessor):
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""" Process unordered list blocks. """
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TAG = 'ul'
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def __init__(self, parser):
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super(UListProcessor, self).__init__(parser)
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# Detect an item (``1. item``). ``group(1)`` contains contents of item.
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self.RE = re.compile(r'^[ ]{0,%d}[*+-][ ]+(.*)' % (self.tab_length - 1))
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class HashHeaderProcessor(BlockProcessor):
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""" Process Hash Headers. """
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# Detect a header at start of any line in block
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RE = re.compile(r'(^|\n)(?P<level>#{1,6})(?P<header>.*?)#*(\n|$)')
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def test(self, parent, block):
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return bool(self.RE.search(block))
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def run(self, parent, blocks):
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block = blocks.pop(0)
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m = self.RE.search(block)
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if m:
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before = block[:m.start()] # All lines before header
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after = block[m.end():] # All lines after header
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if before:
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# As the header was not the first line of the block and the
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# lines before the header must be parsed first,
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# recursively parse this lines as a block.
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self.parser.parseBlocks(parent, [before])
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# Create header using named groups from RE
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h = util.etree.SubElement(parent, 'h%d' % len(m.group('level')))
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h.text = m.group('header').strip()
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if after:
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# Insert remaining lines as first block for future parsing.
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blocks.insert(0, after)
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else: # pragma: no cover
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# This should never happen, but just in case...
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logger.warn("We've got a problem header: %r" % block)
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class SetextHeaderProcessor(BlockProcessor):
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""" Process Setext-style Headers. """
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# Detect Setext-style header. Must be first 2 lines of block.
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RE = re.compile(r'^.*?\n[=-]+[ ]*(\n|$)', re.MULTILINE)
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def test(self, parent, block):
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return bool(self.RE.match(block))
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def run(self, parent, blocks):
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lines = blocks.pop(0).split('\n')
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# Determine level. ``=`` is 1 and ``-`` is 2.
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if lines[1].startswith('='):
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level = 1
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else:
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level = 2
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h = util.etree.SubElement(parent, 'h%d' % level)
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h.text = lines[0].strip()
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if len(lines) > 2:
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# Block contains additional lines. Add to master blocks for later.
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blocks.insert(0, '\n'.join(lines[2:]))
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class HRProcessor(BlockProcessor):
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""" Process Horizontal Rules. """
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RE = r'^[ ]{0,3}((-+[ ]{0,2}){3,}|(_+[ ]{0,2}){3,}|(\*+[ ]{0,2}){3,})[ ]*'
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# Detect hr on any line of a block.
|
|
SEARCH_RE = re.compile(RE, re.MULTILINE)
|
|
|
|
def test(self, parent, block):
|
|
m = self.SEARCH_RE.search(block)
|
|
# No atomic grouping in python so we simulate it here for performance.
|
|
# The regex only matches what would be in the atomic group - the HR.
|
|
# Then check if we are at end of block or if next char is a newline.
|
|
if m and (m.end() == len(block) or block[m.end()] == '\n'):
|
|
# Save match object on class instance so we can use it later.
|
|
self.match = m
|
|
return True
|
|
return False
|
|
|
|
def run(self, parent, blocks):
|
|
block = blocks.pop(0)
|
|
match = self.match
|
|
# Check for lines in block before hr.
|
|
prelines = block[:match.start()].rstrip('\n')
|
|
if prelines:
|
|
# Recursively parse lines before hr so they get parsed first.
|
|
self.parser.parseBlocks(parent, [prelines])
|
|
# create hr
|
|
util.etree.SubElement(parent, 'hr')
|
|
# check for lines in block after hr.
|
|
postlines = block[match.end():].lstrip('\n')
|
|
if postlines:
|
|
# Add lines after hr to master blocks for later parsing.
|
|
blocks.insert(0, postlines)
|
|
|
|
|
|
class EmptyBlockProcessor(BlockProcessor):
|
|
""" Process blocks that are empty or start with an empty line. """
|
|
|
|
def test(self, parent, block):
|
|
return not block or block.startswith('\n')
|
|
|
|
def run(self, parent, blocks):
|
|
block = blocks.pop(0)
|
|
filler = '\n\n'
|
|
if block:
|
|
# Starts with empty line
|
|
# Only replace a single line.
|
|
filler = '\n'
|
|
# Save the rest for later.
|
|
theRest = block[1:]
|
|
if theRest:
|
|
# Add remaining lines to master blocks for later.
|
|
blocks.insert(0, theRest)
|
|
sibling = self.lastChild(parent)
|
|
if (sibling is not None and sibling.tag == 'pre' and
|
|
len(sibling) and sibling[0].tag == 'code'):
|
|
# Last block is a codeblock. Append to preserve whitespace.
|
|
sibling[0].text = util.AtomicString(
|
|
'%s%s' % (sibling[0].text, filler)
|
|
)
|
|
|
|
|
|
class ParagraphProcessor(BlockProcessor):
|
|
""" Process Paragraph blocks. """
|
|
|
|
def test(self, parent, block):
|
|
return True
|
|
|
|
def run(self, parent, blocks):
|
|
block = blocks.pop(0)
|
|
if block.strip():
|
|
# Not a blank block. Add to parent, otherwise throw it away.
|
|
if self.parser.state.isstate('list'):
|
|
# The parent is a tight-list.
|
|
#
|
|
# Check for any children. This will likely only happen in a
|
|
# tight-list when a header isn't followed by a blank line.
|
|
# For example:
|
|
#
|
|
# * # Header
|
|
# Line 2 of list item - not part of header.
|
|
sibling = self.lastChild(parent)
|
|
if sibling is not None:
|
|
# Insetrt after sibling.
|
|
if sibling.tail:
|
|
sibling.tail = '%s\n%s' % (sibling.tail, block)
|
|
else:
|
|
sibling.tail = '\n%s' % block
|
|
else:
|
|
# Append to parent.text
|
|
if parent.text:
|
|
parent.text = '%s\n%s' % (parent.text, block)
|
|
else:
|
|
parent.text = block.lstrip()
|
|
else:
|
|
# Create a regular paragraph
|
|
p = util.etree.SubElement(parent, 'p')
|
|
p.text = block.lstrip()
|