templater: add a few comments.

mercurial/templater.py

@@ -1,286 +1,289
 # templater.py - template expansion for output
 #
 # Copyright 2005, 2006 Matt Mackall <[e-mail]>
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
 from i18n import _
 import sys, os
 import util, config, templatefilters
 
 path = ['templates', '../templates']
 stringify = templatefilters.stringify
 
 def _flatten(thing):
     '''yield a single stream from a possibly nested set of iterators'''
     if isinstance(thing, str):
         yield thing
     elif not hasattr(thing, '__iter__'):
         if thing is not None:
             yield str(thing)
     else:
         for i in thing:
             if isinstance(i, str):
                 yield i
             elif not hasattr(i, '__iter__'):
                 if i is not None:
                     yield str(i)
             elif i is not None:
                 for j in _flatten(i):
                     yield j
 
 def parsestring(s, quoted=True):
     '''parse a string using simple c-like syntax.
     string must be in quotes if quoted is True.'''
     if quoted:
         if len(s) < 2 or s[0] != s[-1]:
             raise SyntaxError(_('unmatched quotes'))
         return s[1:-1].decode('string_escape')
 
     return s.decode('string_escape')
 
 class engine(object):
     '''template expansion engine.
 
     template expansion works like this. a map file contains key=value
     pairs. if value is quoted, it is treated as string. otherwise, it
     is treated as name of template file.
 
     templater is asked to expand a key in map. it looks up key, and
     looks for strings like this: {foo}. it expands {foo} by looking up
     foo in map, and substituting it. expansion is recursive: it stops
     when there is no more {foo} to replace.
 
     expansion also allows formatting and filtering.
 
     format uses key to expand each item in list. syntax is
     {key%format}.
 
     filter uses function to transform value. syntax is
     {key|filter1|filter2|...}.'''
 
     def __init__(self, loader, filters={}, defaults={}):
         self._loader = loader
         self._filters = filters
         self._defaults = defaults
         self._cache = {}
 
     def process(self, t, mapping):
         '''Perform expansion. t is name of map element to expand.
         mapping contains added elements for use during expansion. Is a
         generator.'''
         return _flatten(self._process(self._load(t), mapping))
 
     def _load(self, t):
         '''load, parse, and cache a template'''
         if t not in self._cache:
             self._cache[t] = self._parse(self._loader(t))
         return self._cache[t]
 
     def _get(self, mapping, key):
         v = mapping.get(key)
         if v is None:
             v = self._defaults.get(key, '')
         if hasattr(v, '__call__'):
             v = v(**mapping)
         return v
 
     def _filter(self, mapping, parts):
         filters, val = parts
         x = self._get(mapping, val)
         for f in filters:
             x = f(x)
         return x
 
     def _format(self, mapping, args):
         key, parsed = args
         v = self._get(mapping, key)
         if not hasattr(v, '__iter__'):
             raise SyntaxError(_("error expanding '%s%%%s'")
                               % (key, format))
         lm = mapping.copy()
         for i in v:
             if isinstance(i, dict):
                 lm.update(i)
                 yield self._process(parsed, lm)
             else:
                 # v is not an iterable of dicts, this happen when 'key'
                 # has been fully expanded already and format is useless.
                 # If so, return the expanded value.
                 yield i
 
     def _parse(self, tmpl):
         '''preparse a template'''
         parsed = []
         pos, stop = 0, len(tmpl)
         while pos < stop:
             n = tmpl.find('{', pos)
             if n < 0:
                 parsed.append((None, tmpl[pos:stop]))
                 break
             if n > 0 and tmpl[n - 1] == '\\':
                 # escaped
                 parsed.append((None, tmpl[pos:n - 1] + "{"))
                 pos = n + 1
                 continue
             if n > pos:
                 parsed.append((None, tmpl[pos:n]))
 
             pos = n
             n = tmpl.find('}', pos)
             if n < 0:
                 # no closing
                 parsed.append((None, tmpl[pos:stop]))
                 break
 
             expr = tmpl[pos + 1:n]
             pos = n + 1
 
             if '%' in expr:
+                # the keyword should be formatted with a template
                 key, t = expr.split('%')
                 parsed.append((self._format, (key.strip(),
                                               self._load(t.strip()))))
             elif '|' in expr:
+                # process the keyword value with one or more filters
                 parts = expr.split('|')
                 val = parts[0].strip()
                 try:
                     filters = [self._filters[f.strip()] for f in parts[1:]]
                 except KeyError, i:
                     raise SyntaxError(_("unknown filter '%s'") % i[0])
                 parsed.append((self._filter, (filters, val)))
             else:
+                # just get the keyword
                 parsed.append((self._get, expr.strip()))
 
         return parsed
 
     def _process(self, parsed, mapping):
         '''Render a template. Returns a generator.'''
         for f, e in parsed:
             if f:
                 yield f(mapping, e)
             else:
                 yield e
 
 engines = {'default': engine}
 
 class templater(object):
 
     def __init__(self, mapfile, filters={}, defaults={}, cache={},
                  minchunk=1024, maxchunk=65536):
         '''set up template engine.
         mapfile is name of file to read map definitions from.
         filters is dict of functions. each transforms a value into another.
         defaults is dict of default map definitions.'''
         self.mapfile = mapfile or 'template'
         self.cache = cache.copy()
         self.map = {}
         self.base = (mapfile and os.path.dirname(mapfile)) or ''
         self.filters = templatefilters.filters.copy()
         self.filters.update(filters)
         self.defaults = defaults
         self.minchunk, self.maxchunk = minchunk, maxchunk
         self.engines = {}
 
         if not mapfile:
             return
         if not os.path.exists(mapfile):
             raise util.Abort(_('style not found: %s') % mapfile)
 
         conf = config.config()
         conf.read(mapfile)
 
         for key, val in conf[''].items():
             if val[0] in "'\"":
                 try:
                     self.cache[key] = parsestring(val)
                 except SyntaxError, inst:
                     raise SyntaxError('%s: %s' %
                                       (conf.source('', key), inst.args[0]))
             else:
                 val = 'default', val
                 if ':' in val[1]:
                     val = val[1].split(':', 1)
                 self.map[key] = val[0], os.path.join(self.base, val[1])
 
     def __contains__(self, key):
         return key in self.cache or key in self.map
 
     def load(self, t):
         '''Get the template for the given template name. Use a local cache.'''
         if not t in self.cache:
             try:
                 self.cache[t] = open(self.map[t][1]).read()
             except IOError, inst:
                 raise IOError(inst.args[0], _('template file %s: %s') %
                               (self.map[t][1], inst.args[1]))
         return self.cache[t]
 
     def __call__(self, t, **mapping):
         ttype = t in self.map and self.map[t][0] or 'default'
         proc = self.engines.get(ttype)
         if proc is None:
             proc = engines[ttype](self.load, self.filters, self.defaults)
             self.engines[ttype] = proc
 
         stream = proc.process(t, mapping)
         if self.minchunk:
             stream = util.increasingchunks(stream, min=self.minchunk,
                                            max=self.maxchunk)
         return stream
 
 def templatepath(name=None):
     '''return location of template file or directory (if no name).
     returns None if not found.'''
     normpaths = []
 
     # executable version (py2exe) doesn't support __file__
     if hasattr(sys, 'frozen'):
         module = sys.executable
     else:
         module = __file__
     for f in path:
         if f.startswith('/'):
             p = f
         else:
             fl = f.split('/')
             p = os.path.join(os.path.dirname(module), *fl)
         if name:
             p = os.path.join(p, name)
         if name and os.path.exists(p):
             return os.path.normpath(p)
         elif os.path.isdir(p):
             normpaths.append(os.path.normpath(p))
 
     return normpaths
 
 def stylemap(styles, paths=None):
     """Return path to mapfile for a given style.
 
     Searches mapfile in the following locations:
     1. templatepath/style/map
     2. templatepath/map-style
     3. templatepath/map
     """
 
     if paths is None:
         paths = templatepath()
     elif isinstance(paths, str):
         paths = [paths]
 
     if isinstance(styles, str):
         styles = [styles]
 
     for style in styles:
         if not style:
             continue
         locations = [os.path.join(style, 'map'), 'map-' + style]
         locations.append('map')
 
         for path in paths:
             for location in locations:
                 mapfile = os.path.join(path, location)
                 if os.path.isfile(mapfile):
                     return style, mapfile
 
     raise RuntimeError("No hgweb templates found in %r" % paths)