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Diffstat (limited to 'source-builder/sb/markdown/blockprocessors.py')
-rw-r--r-- | source-builder/sb/markdown/blockprocessors.py | 573 |
1 files changed, 573 insertions, 0 deletions
diff --git a/source-builder/sb/markdown/blockprocessors.py b/source-builder/sb/markdown/blockprocessors.py new file mode 100644 index 0000000..a3ed977 --- /dev/null +++ b/source-builder/sb/markdown/blockprocessors.py @@ -0,0 +1,573 @@ +""" +CORE MARKDOWN BLOCKPARSER +=========================================================================== + +This parser handles basic parsing of Markdown blocks. It doesn't concern +itself with inline elements such as **bold** or *italics*, but rather just +catches blocks, lists, quotes, etc. + +The BlockParser is made up of a bunch of BlockProssors, each handling a +different type of block. Extensions may add/replace/remove BlockProcessors +as they need to alter how markdown blocks are parsed. +""" + +from __future__ import absolute_import +from __future__ import division +from __future__ import unicode_literals +import logging +import re +from . import util +from .blockparser import BlockParser + +logger = logging.getLogger('MARKDOWN') + + +def build_block_parser(md_instance, **kwargs): + """ Build the default block parser used by Markdown. """ + parser = BlockParser(md_instance) + parser.blockprocessors['empty'] = EmptyBlockProcessor(parser) + parser.blockprocessors['indent'] = ListIndentProcessor(parser) + parser.blockprocessors['code'] = CodeBlockProcessor(parser) + parser.blockprocessors['hashheader'] = HashHeaderProcessor(parser) + parser.blockprocessors['setextheader'] = SetextHeaderProcessor(parser) + parser.blockprocessors['hr'] = HRProcessor(parser) + parser.blockprocessors['olist'] = OListProcessor(parser) + parser.blockprocessors['ulist'] = UListProcessor(parser) + parser.blockprocessors['quote'] = BlockQuoteProcessor(parser) + parser.blockprocessors['paragraph'] = ParagraphProcessor(parser) + return parser + + +class BlockProcessor(object): + """ Base class for block processors. + + Each subclass will provide the methods below to work with the source and + tree. Each processor will need to define it's own ``test`` and ``run`` + methods. The ``test`` method should return True or False, to indicate + whether the current block should be processed by this processor. If the + test passes, the parser will call the processors ``run`` method. + + """ + + def __init__(self, parser): + self.parser = parser + self.tab_length = parser.markdown.tab_length + + def lastChild(self, parent): + """ Return the last child of an etree element. """ + if len(parent): + return parent[-1] + else: + return None + + def detab(self, text): + """ Remove a tab from the front of each line of the given text. """ + newtext = [] + lines = text.split('\n') + for line in lines: + if line.startswith(' '*self.tab_length): + newtext.append(line[self.tab_length:]) + elif not line.strip(): + newtext.append('') + else: + break + return '\n'.join(newtext), '\n'.join(lines[len(newtext):]) + + def looseDetab(self, text, level=1): + """ Remove a tab from front of lines but allowing dedented lines. """ + lines = text.split('\n') + for i in range(len(lines)): + if lines[i].startswith(' '*self.tab_length*level): + lines[i] = lines[i][self.tab_length*level:] + return '\n'.join(lines) + + def test(self, parent, block): + """ Test for block type. Must be overridden by subclasses. + + As the parser loops through processors, it will call the ``test`` + method on each to determine if the given block of text is of that + type. This method must return a boolean ``True`` or ``False``. The + actual method of testing is left to the needs of that particular + block type. It could be as simple as ``block.startswith(some_string)`` + or a complex regular expression. As the block type may be different + depending on the parent of the block (i.e. inside a list), the parent + etree element is also provided and may be used as part of the test. + + Keywords: + + * ``parent``: A etree element which will be the parent of the block. + * ``block``: A block of text from the source which has been split at + blank lines. + """ + pass # pragma: no cover + + def run(self, parent, blocks): + """ Run processor. Must be overridden by subclasses. + + When the parser determines the appropriate type of a block, the parser + will call the corresponding processor's ``run`` method. This method + should parse the individual lines of the block and append them to + the etree. + + Note that both the ``parent`` and ``etree`` keywords are pointers + to instances of the objects which should be edited in place. Each + processor must make changes to the existing objects as there is no + mechanism to return new/different objects to replace them. + + This means that this method should be adding SubElements or adding text + to the parent, and should remove (``pop``) or add (``insert``) items to + the list of blocks. + + Keywords: + + * ``parent``: A etree element which is the parent of the current block. + * ``blocks``: A list of all remaining blocks of the document. + """ + pass # pragma: no cover + + +class ListIndentProcessor(BlockProcessor): + """ Process children of list items. + + Example: + * a list item + process this part + + or this part + + """ + + ITEM_TYPES = ['li'] + LIST_TYPES = ['ul', 'ol'] + + def __init__(self, *args): + super(ListIndentProcessor, self).__init__(*args) + self.INDENT_RE = re.compile(r'^(([ ]{%s})+)' % self.tab_length) + + def test(self, parent, block): + return block.startswith(' '*self.tab_length) and \ + not self.parser.state.isstate('detabbed') and \ + (parent.tag in self.ITEM_TYPES or + (len(parent) and parent[-1] is not None and + (parent[-1].tag in self.LIST_TYPES))) + + def run(self, parent, blocks): + block = blocks.pop(0) + level, sibling = self.get_level(parent, block) + block = self.looseDetab(block, level) + + self.parser.state.set('detabbed') + if parent.tag in self.ITEM_TYPES: + # It's possible that this parent has a 'ul' or 'ol' child list + # with a member. If that is the case, then that should be the + # parent. This is intended to catch the edge case of an indented + # list whose first member was parsed previous to this point + # see OListProcessor + if len(parent) and parent[-1].tag in self.LIST_TYPES: + self.parser.parseBlocks(parent[-1], [block]) + else: + # The parent is already a li. Just parse the child block. + self.parser.parseBlocks(parent, [block]) + elif sibling.tag in self.ITEM_TYPES: + # The sibling is a li. Use it as parent. + self.parser.parseBlocks(sibling, [block]) + elif len(sibling) and sibling[-1].tag in self.ITEM_TYPES: + # The parent is a list (``ol`` or ``ul``) which has children. + # Assume the last child li is the parent of this block. + if sibling[-1].text: + # If the parent li has text, that text needs to be moved to a p + # The p must be 'inserted' at beginning of list in the event + # that other children already exist i.e.; a nested sublist. + p = util.etree.Element('p') + p.text = sibling[-1].text + sibling[-1].text = '' + sibling[-1].insert(0, p) + self.parser.parseChunk(sibling[-1], block) + else: + self.create_item(sibling, block) + self.parser.state.reset() + + def create_item(self, parent, block): + """ Create a new li and parse the block with it as the parent. """ + li = util.etree.SubElement(parent, 'li') + self.parser.parseBlocks(li, [block]) + + def get_level(self, parent, block): + """ Get level of indent based on list level. """ + # Get indent level + m = self.INDENT_RE.match(block) + if m: + indent_level = len(m.group(1))/self.tab_length + else: + indent_level = 0 + if self.parser.state.isstate('list'): + # We're in a tightlist - so we already are at correct parent. + level = 1 + else: + # We're in a looselist - so we need to find parent. + level = 0 + # Step through children of tree to find matching indent level. + while indent_level > level: + child = self.lastChild(parent) + if (child is not None and + (child.tag in self.LIST_TYPES or child.tag in self.ITEM_TYPES)): + if child.tag in self.LIST_TYPES: + level += 1 + parent = child + else: + # No more child levels. If we're short of indent_level, + # we have a code block. So we stop here. + break + return level, parent + + +class CodeBlockProcessor(BlockProcessor): + """ Process code blocks. """ + + def test(self, parent, block): + return block.startswith(' '*self.tab_length) + + def run(self, parent, blocks): + sibling = self.lastChild(parent) + block = blocks.pop(0) + theRest = '' + if (sibling is not None and sibling.tag == "pre" and + len(sibling) and sibling[0].tag == "code"): + # The previous block was a code block. As blank lines do not start + # new code blocks, append this block to the previous, adding back + # linebreaks removed from the split into a list. + code = sibling[0] + block, theRest = self.detab(block) + code.text = util.AtomicString( + '%s\n%s\n' % (code.text, block.rstrip()) + ) + else: + # This is a new codeblock. Create the elements and insert text. + pre = util.etree.SubElement(parent, 'pre') + code = util.etree.SubElement(pre, 'code') + block, theRest = self.detab(block) + code.text = util.AtomicString('%s\n' % block.rstrip()) + if theRest: + # This block contained unindented line(s) after the first indented + # line. Insert these lines as the first block of the master blocks + # list for future processing. + blocks.insert(0, theRest) + + +class BlockQuoteProcessor(BlockProcessor): + + RE = re.compile(r'(^|\n)[ ]{0,3}>[ ]?(.*)') + + def test(self, parent, block): + return bool(self.RE.search(block)) + + def run(self, parent, blocks): + block = blocks.pop(0) + m = self.RE.search(block) + if m: + before = block[:m.start()] # Lines before blockquote + # Pass lines before blockquote in recursively for parsing forst. + self.parser.parseBlocks(parent, [before]) + # Remove ``> `` from begining of each line. + block = '\n'.join( + [self.clean(line) for line in block[m.start():].split('\n')] + ) + sibling = self.lastChild(parent) + if sibling is not None and sibling.tag == "blockquote": + # Previous block was a blockquote so set that as this blocks parent + quote = sibling + else: + # This is a new blockquote. Create a new parent element. + quote = util.etree.SubElement(parent, 'blockquote') + # Recursively parse block with blockquote as parent. + # change parser state so blockquotes embedded in lists use p tags + self.parser.state.set('blockquote') + self.parser.parseChunk(quote, block) + self.parser.state.reset() + + def clean(self, line): + """ Remove ``>`` from beginning of a line. """ + m = self.RE.match(line) + if line.strip() == ">": + return "" + elif m: + return m.group(2) + else: + return line + + +class OListProcessor(BlockProcessor): + """ Process ordered list blocks. """ + + TAG = 'ol' + # The integer (python string) with which the lists starts (default=1) + # Eg: If list is intialized as) + # 3. Item + # The ol tag will get starts="3" attribute + STARTSWITH = '1' + # List of allowed sibling tags. + SIBLING_TAGS = ['ol', 'ul'] + + def __init__(self, parser): + super(OListProcessor, self).__init__(parser) + # Detect an item (``1. item``). ``group(1)`` contains contents of item. + self.RE = re.compile(r'^[ ]{0,%d}\d+\.[ ]+(.*)' % (self.tab_length - 1)) + # Detect items on secondary lines. they can be of either list type. + self.CHILD_RE = re.compile(r'^[ ]{0,%d}((\d+\.)|[*+-])[ ]+(.*)' % + (self.tab_length - 1)) + # Detect indented (nested) items of either type + self.INDENT_RE = re.compile(r'^[ ]{%d,%d}((\d+\.)|[*+-])[ ]+.*' % + (self.tab_length, self.tab_length * 2 - 1)) + + def test(self, parent, block): + return bool(self.RE.match(block)) + + def run(self, parent, blocks): + # Check fr multiple items in one block. + items = self.get_items(blocks.pop(0)) + sibling = self.lastChild(parent) + + if sibling is not None and sibling.tag in self.SIBLING_TAGS: + # Previous block was a list item, so set that as parent + lst = sibling + # make sure previous item is in a p- if the item has text, + # then it isn't in a p + if lst[-1].text: + # since it's possible there are other children for this + # sibling, we can't just SubElement the p, we need to + # insert it as the first item. + p = util.etree.Element('p') + p.text = lst[-1].text + lst[-1].text = '' + lst[-1].insert(0, p) + # if the last item has a tail, then the tail needs to be put in a p + # likely only when a header is not followed by a blank line + lch = self.lastChild(lst[-1]) + if lch is not None and lch.tail: + p = util.etree.SubElement(lst[-1], 'p') + p.text = lch.tail.lstrip() + lch.tail = '' + + # parse first block differently as it gets wrapped in a p. + li = util.etree.SubElement(lst, 'li') + self.parser.state.set('looselist') + firstitem = items.pop(0) + self.parser.parseBlocks(li, [firstitem]) + self.parser.state.reset() + elif parent.tag in ['ol', 'ul']: + # this catches the edge case of a multi-item indented list whose + # first item is in a blank parent-list item: + # * * subitem1 + # * subitem2 + # see also ListIndentProcessor + lst = parent + else: + # This is a new list so create parent with appropriate tag. + lst = util.etree.SubElement(parent, self.TAG) + # Check if a custom start integer is set + if not self.parser.markdown.lazy_ol and self.STARTSWITH != '1': + lst.attrib['start'] = self.STARTSWITH + + self.parser.state.set('list') + # Loop through items in block, recursively parsing each with the + # appropriate parent. + for item in items: + if item.startswith(' '*self.tab_length): + # Item is indented. Parse with last item as parent + self.parser.parseBlocks(lst[-1], [item]) + else: + # New item. Create li and parse with it as parent + li = util.etree.SubElement(lst, 'li') + self.parser.parseBlocks(li, [item]) + self.parser.state.reset() + + def get_items(self, block): + """ Break a block into list items. """ + items = [] + for line in block.split('\n'): + m = self.CHILD_RE.match(line) + if m: + # This is a new list item + # Check first item for the start index + if not items and self.TAG == 'ol': + # Detect the integer value of first list item + INTEGER_RE = re.compile('(\d+)') + self.STARTSWITH = INTEGER_RE.match(m.group(1)).group() + # Append to the list + items.append(m.group(3)) + elif self.INDENT_RE.match(line): + # This is an indented (possibly nested) item. + if items[-1].startswith(' '*self.tab_length): + # Previous item was indented. Append to that item. + items[-1] = '%s\n%s' % (items[-1], line) + else: + items.append(line) + else: + # This is another line of previous item. Append to that item. + items[-1] = '%s\n%s' % (items[-1], line) + return items + + +class UListProcessor(OListProcessor): + """ Process unordered list blocks. """ + + TAG = 'ul' + + def __init__(self, parser): + super(UListProcessor, self).__init__(parser) + # Detect an item (``1. item``). ``group(1)`` contains contents of item. + self.RE = re.compile(r'^[ ]{0,%d}[*+-][ ]+(.*)' % (self.tab_length - 1)) + + +class HashHeaderProcessor(BlockProcessor): + """ Process Hash Headers. """ + + # Detect a header at start of any line in block + RE = re.compile(r'(^|\n)(?P<level>#{1,6})(?P<header>.*?)#*(\n|$)') + + def test(self, parent, block): + return bool(self.RE.search(block)) + + def run(self, parent, blocks): + block = blocks.pop(0) + m = self.RE.search(block) + if m: + before = block[:m.start()] # All lines before header + after = block[m.end():] # All lines after header + if before: + # As the header was not the first line of the block and the + # lines before the header must be parsed first, + # recursively parse this lines as a block. + self.parser.parseBlocks(parent, [before]) + # Create header using named groups from RE + h = util.etree.SubElement(parent, 'h%d' % len(m.group('level'))) + h.text = m.group('header').strip() + if after: + # Insert remaining lines as first block for future parsing. + blocks.insert(0, after) + else: # pragma: no cover + # This should never happen, but just in case... + logger.warn("We've got a problem header: %r" % block) + + +class SetextHeaderProcessor(BlockProcessor): + """ Process Setext-style Headers. """ + + # Detect Setext-style header. Must be first 2 lines of block. + RE = re.compile(r'^.*?\n[=-]+[ ]*(\n|$)', re.MULTILINE) + + def test(self, parent, block): + return bool(self.RE.match(block)) + + def run(self, parent, blocks): + lines = blocks.pop(0).split('\n') + # Determine level. ``=`` is 1 and ``-`` is 2. + if lines[1].startswith('='): + level = 1 + else: + level = 2 + h = util.etree.SubElement(parent, 'h%d' % level) + h.text = lines[0].strip() + if len(lines) > 2: + # Block contains additional lines. Add to master blocks for later. + blocks.insert(0, '\n'.join(lines[2:])) + + +class HRProcessor(BlockProcessor): + """ Process Horizontal Rules. """ + + RE = r'^[ ]{0,3}((-+[ ]{0,2}){3,}|(_+[ ]{0,2}){3,}|(\*+[ ]{0,2}){3,})[ ]*' + # 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() |