minirst: refactor/simplify findblocks

mercurial/minirst.py

@@ -1,441 +1,437
 # minirst.py - minimal reStructuredText parser
 #
 # Copyright 2009, 2010 Matt Mackall <[e-mail]> and others
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
 """simplified reStructuredText parser.
 
 This parser knows just enough about reStructuredText to parse the
 Mercurial docstrings.
 
 It cheats in a major way: nested blocks are not really nested. They
 are just indented blocks that look like they are nested. This relies
 on the user to keep the right indentation for the blocks.
 
 It only supports a small subset of reStructuredText:
 
 - sections
 
 - paragraphs
 
 - literal blocks
 
 - definition lists
 
 - specific admonitions
 
 - bullet lists (items must start with '-')
 
 - enumerated lists (no autonumbering)
 
 - field lists (colons cannot be escaped)
 
 - option lists (supports only long options without arguments)
 
 - inline literals (no other inline markup is not recognized)
 """
 
 import re, sys
 import util, encoding
 from i18n import _
 
 
 def replace(text, substs):
     utext = text.decode(encoding.encoding)
     for f, t in substs:
         utext = utext.replace(f, t)
     return utext.encode(encoding.encoding)
 
+
+_blockre = re.compile(r"\n(?:\s*\n)+")
+
 def findblocks(text):
     """Find continuous blocks of lines in text.
 
     Returns a list of dictionaries representing the blocks. Each block
     has an 'indent' field and a 'lines' field.
     """
-    blocks = [[]]
-    lines = text.splitlines()
-    for line in lines:
-        if line.strip():
-            blocks[-1].append(line)
-        elif blocks[-1]:
-            blocks.append([])
-    if not blocks[-1]:
-        del blocks[-1]
-
-    for i, block in enumerate(blocks):
-        indent = min((len(l) - len(l.lstrip())) for l in block)
-        blocks[i] = dict(indent=indent, lines=[l[indent:] for l in block])
+    blocks = []
+    for b in _blockre.split(text.strip()):
+        lines = b.splitlines()
+        indent = min((len(l) - len(l.lstrip())) for l in lines)
+        lines = [l[indent:] for l in lines]
+        blocks.append(dict(indent=indent, lines=lines))
     return blocks
 
 
 def findliteralblocks(blocks):
     """Finds literal blocks and adds a 'type' field to the blocks.
 
     Literal blocks are given the type 'literal', all other blocks are
     given type the 'paragraph'.
     """
     i = 0
     while i < len(blocks):
         # Searching for a block that looks like this:
         #
         # +------------------------------+
         # | paragraph                    |
         # | (ends with "::")             |
         # +------------------------------+
         #    +---------------------------+
         #    | indented literal block    |
         #    +---------------------------+
         blocks[i]['type'] = 'paragraph'
         if blocks[i]['lines'][-1].endswith('::') and i + 1 < len(blocks):
             indent = blocks[i]['indent']
             adjustment = blocks[i + 1]['indent'] - indent
 
             if blocks[i]['lines'] == ['::']:
                 # Expanded form: remove block
                 del blocks[i]
                 i -= 1
             elif blocks[i]['lines'][-1].endswith(' ::'):
                 # Partially minimized form: remove space and both
                 # colons.
                 blocks[i]['lines'][-1] = blocks[i]['lines'][-1][:-3]
             else:
                 # Fully minimized form: remove just one colon.
                 blocks[i]['lines'][-1] = blocks[i]['lines'][-1][:-1]
 
             # List items are formatted with a hanging indent. We must
             # correct for this here while we still have the original
             # information on the indentation of the subsequent literal
             # blocks available.
             m = _bulletre.match(blocks[i]['lines'][0])
             if m:
                 indent += m.end()
                 adjustment -= m.end()
 
             # Mark the following indented blocks.
             while i + 1 < len(blocks) and blocks[i + 1]['indent'] > indent:
                 blocks[i + 1]['type'] = 'literal'
                 blocks[i + 1]['indent'] -= adjustment
                 i += 1
         i += 1
     return blocks
 
 _bulletre = re.compile(r'(-|[0-9A-Za-z]+\.|\(?[0-9A-Za-z]+\)|\|) ')
 _optionre = re.compile(r'^(--[a-z-]+)((?:[ =][a-zA-Z][\w-]*)?  +)(.*)$')
 _fieldre = re.compile(r':(?![: ])([^:]*)(?<! ):[ ]+(.*)')
 _definitionre = re.compile(r'[^ ]')
 
 def splitparagraphs(blocks):
     """Split paragraphs into lists."""
     # Tuples with (list type, item regexp, single line items?). Order
     # matters: definition lists has the least specific regexp and must
     # come last.
     listtypes = [('bullet', _bulletre, True),
                  ('option', _optionre, True),
                  ('field', _fieldre, True),
                  ('definition', _definitionre, False)]
 
     def match(lines, i, itemre, singleline):
         """Does itemre match an item at line i?
 
         A list item can be followed by an idented line or another list
         item (but only if singleline is True).
         """
         line1 = lines[i]
         line2 = i + 1 < len(lines) and lines[i + 1] or ''
         if not itemre.match(line1):
             return False
         if singleline:
             return line2 == '' or line2[0] == ' ' or itemre.match(line2)
         else:
             return line2.startswith(' ')
 
     i = 0
     while i < len(blocks):
         if blocks[i]['type'] == 'paragraph':
             lines = blocks[i]['lines']
             for type, itemre, singleline in listtypes:
                 if match(lines, 0, itemre, singleline):
                     items = []
                     for j, line in enumerate(lines):
                         if match(lines, j, itemre, singleline):
                             items.append(dict(type=type, lines=[],
                                               indent=blocks[i]['indent']))
                         items[-1]['lines'].append(line)
                     blocks[i:i + 1] = items
                     break
         i += 1
     return blocks
 
 
 _fieldwidth = 12
 
 def updatefieldlists(blocks):
     """Find key and maximum key width for field lists."""
     i = 0
     while i < len(blocks):
         if blocks[i]['type'] != 'field':
             i += 1
             continue
 
         keywidth = 0
         j = i
         while j < len(blocks) and blocks[j]['type'] == 'field':
             m = _fieldre.match(blocks[j]['lines'][0])
             key, rest = m.groups()
             blocks[j]['lines'][0] = rest
             blocks[j]['key'] = key
             keywidth = max(keywidth, len(key))
             j += 1
 
         for block in blocks[i:j]:
             block['keywidth'] = keywidth
         i = j + 1
 
     return blocks
 
 
 def prunecontainers(blocks, keep):
     """Prune unwanted containers.
 
     The blocks must have a 'type' field, i.e., they should have been
     run through findliteralblocks first.
     """
     pruned = []
     i = 0
     while i + 1 < len(blocks):
         # Searching for a block that looks like this:
         #
         # +-------+---------------------------+
         # | ".. container ::" type            |
         # +---+                               |
         #     | blocks                        |
         #     +-------------------------------+
         if (blocks[i]['type'] == 'paragraph' and
             blocks[i]['lines'][0].startswith('.. container::')):
             indent = blocks[i]['indent']
             adjustment = blocks[i + 1]['indent'] - indent
             containertype = blocks[i]['lines'][0][15:]
             prune = containertype not in keep
             if prune:
                 pruned.append(containertype)
 
             # Always delete "..container:: type" block
             del blocks[i]
             j = i
             while j < len(blocks) and blocks[j]['indent'] > indent:
                 if prune:
                     del blocks[j]
                     i -= 1 # adjust outer index
                 else:
                     blocks[j]['indent'] -= adjustment
                     j += 1
         i += 1
     return blocks, pruned
 
 
 _sectionre = re.compile(r"""^([-=`:.'"~^_*+#])\1+$""")
 
 def findsections(blocks):
     """Finds sections.
 
     The blocks must have a 'type' field, i.e., they should have been
     run through findliteralblocks first.
     """
     for block in blocks:
         # Searching for a block that looks like this:
         #
         # +------------------------------+
         # | Section title                |
         # | -------------                |
         # +------------------------------+
         if (block['type'] == 'paragraph' and
             len(block['lines']) == 2 and
             len(block['lines'][0]) == len(block['lines'][1]) and
             _sectionre.match(block['lines'][1])):
             block['underline'] = block['lines'][1][0]
             block['type'] = 'section'
             del block['lines'][1]
     return blocks
 
 
 def inlineliterals(blocks):
     substs = [('``', '"')]
     for b in blocks:
         if b['type'] in ('paragraph', 'section'):
             b['lines'] = [replace(l, substs) for l in b['lines']]
     return blocks
 
 
 def hgrole(blocks):
     substs = [(':hg:`', '"hg '), ('`', '"')]
     for b in blocks:
         if b['type'] in ('paragraph', 'section'):
             # Turn :hg:`command` into "hg command". This also works
             # when there is a line break in the command and relies on
             # the fact that we have no stray back-quotes in the input
             # (run the blocks through inlineliterals first).
             b['lines'] = [replace(l, substs) for l in b['lines']]
     return blocks
 
 
 def addmargins(blocks):
     """Adds empty blocks for vertical spacing.
 
     This groups bullets, options, and definitions together with no vertical
     space between them, and adds an empty block between all other blocks.
     """
     i = 1
     while i < len(blocks):
         if (blocks[i]['type'] == blocks[i - 1]['type'] and
             blocks[i]['type'] in ('bullet', 'option', 'field')):
             i += 1
         else:
             blocks.insert(i, dict(lines=[''], indent=0, type='margin'))
             i += 2
     return blocks
 
 _admonitionre = re.compile(r"\.\. (admonition|attention|caution|danger|"
                            r"error|hint|important|note|tip|warning)::",
                            flags=re.IGNORECASE)
 
 def findadmonitions(blocks):
     """
     Makes the type of the block an admonition block if
     the first line is an admonition directive
     """
     i = 0
     while i < len(blocks):
         m = _admonitionre.match(blocks[i]['lines'][0])
         if m:
             blocks[i]['type'] = 'admonition'
             admonitiontitle = blocks[i]['lines'][0][3:m.end() - 2].lower()
 
             firstline = blocks[i]['lines'][0][m.end() + 1:]
             if firstline:
                 blocks[i]['lines'].insert(1, '   ' + firstline)
 
             blocks[i]['admonitiontitle'] = admonitiontitle
             del blocks[i]['lines'][0]
         i = i + 1
     return blocks
 
 def formatblock(block, width):
     """Format a block according to width."""
     if width <= 0:
         width = 78
     indent = ' ' * block['indent']
     if block['type'] == 'admonition':
         titles = {'attention': _('Attention:'),
                   'caution': _('Caution:'),
                   'danger': _('!Danger!')  ,
                   'error': _('Error:'),
                   'hint': _('Hint:'),
                   'important': _('Important:'),
                   'note': _('Note:'),
                   'tip': _('Tip:'),
                   'warning': _('Warning!')}
 
         admonition = titles[block['admonitiontitle']]
         hang = len(block['lines'][-1]) - len(block['lines'][-1].lstrip())
 
         defindent = indent + hang * ' '
         text = ' '.join(map(str.strip, block['lines']))
         return '%s\n%s' % (indent + admonition, util.wrap(text, width=width,
                                            initindent=defindent,
                                            hangindent=defindent))
     if block['type'] == 'margin':
         return ''
     if block['type'] == 'literal':
         indent += '  '
         return indent + ('\n' + indent).join(block['lines'])
     if block['type'] == 'section':
         underline = len(block['lines'][0]) * block['underline']
         return "%s%s\n%s%s" % (indent, block['lines'][0],indent, underline)
     if block['type'] == 'definition':
         term = indent + block['lines'][0]
         hang = len(block['lines'][-1]) - len(block['lines'][-1].lstrip())
         defindent = indent + hang * ' '
         text = ' '.join(map(str.strip, block['lines'][1:]))
         return '%s\n%s' % (term, util.wrap(text, width=width,
                                            initindent=defindent,
                                            hangindent=defindent))
     subindent = indent
     if block['type'] == 'bullet':
         if block['lines'][0].startswith('| '):
             # Remove bullet for line blocks and add no extra
             # indention.
             block['lines'][0] = block['lines'][0][2:]
         else:
             m = _bulletre.match(block['lines'][0])
             subindent = indent + m.end() * ' '
     elif block['type'] == 'field':
         keywidth = block['keywidth']
         key = block['key']
 
         subindent = indent + _fieldwidth * ' '
         if len(key) + 2 > _fieldwidth:
             # key too large, use full line width
             key = key.ljust(width)
         elif keywidth + 2 < _fieldwidth:
             # all keys are small, add only two spaces
             key = key.ljust(keywidth + 2)
             subindent = indent + (keywidth + 2) * ' '
         else:
             # mixed sizes, use fieldwidth for this one
             key = key.ljust(_fieldwidth)
         block['lines'][0] = key + block['lines'][0]
     elif block['type'] == 'option':
         m = _optionre.match(block['lines'][0])
         option, arg, rest = m.groups()
         subindent = indent + (len(option) + len(arg)) * ' '
 
     text = ' '.join(map(str.strip, block['lines']))
     return util.wrap(text, width=width,
                      initindent=indent,
                      hangindent=subindent)
 
 
 def format(text, width, indent=0, keep=None):
     """Parse and format the text according to width."""
     blocks = findblocks(text)
     for b in blocks:
         b['indent'] += indent
     blocks = findliteralblocks(blocks)
     blocks, pruned = prunecontainers(blocks, keep or [])
     blocks = findsections(blocks)
     blocks = inlineliterals(blocks)
     blocks = hgrole(blocks)
     blocks = splitparagraphs(blocks)
     blocks = updatefieldlists(blocks)
     blocks = addmargins(blocks)
     blocks = findadmonitions(blocks)
     text = '\n'.join(formatblock(b, width) for b in blocks)
     if keep is None:
         return text
     else:
         return text, pruned
 
 
 if __name__ == "__main__":
     from pprint import pprint
 
     def debug(func, *args):
         blocks = func(*args)
         print "*** after %s:" % func.__name__
         pprint(blocks)
         print
         return blocks
 
     text = open(sys.argv[1]).read()
     blocks = debug(findblocks, text)
     blocks = debug(findliteralblocks, blocks)
     blocks, pruned = debug(prunecontainers, blocks, sys.argv[2:])
     blocks = debug(inlineliterals, blocks)
     blocks = debug(splitparagraphs, blocks)
     blocks = debug(updatefieldlists, blocks)
     blocks = debug(findsections, blocks)
     blocks = debug(addmargins, blocks)
     blocks = debug(findadmonitions, blocks)
     print '\n'.join(formatblock(b, 30) for b in blocks)