python/helpers/epydoc/markup/__init__.py - platform/tools/idea - Git at Google

 #
 # epydoc package file
 #
 # A python documentation Module
 # Edward Loper
 #
 # $Id: __init__.py 1577 2007-03-09 23:26:21Z dvarrazzo $
 #

 """
 Markup language support for docstrings.  Each submodule defines a
 parser for a single markup language.  These parsers convert an
 object's docstring to a L{ParsedDocstring}, a standard intermediate
 representation that can be used to generate output.
 C{ParsedDocstring}s support the following operations:
   - output generation (L{to_plaintext()<ParsedDocstring.to_plaintext>},
     L{to_html()<ParsedDocstring.to_html>}, and
     L{to_latex()<ParsedDocstring.to_latex>}).
   - Summarization (L{summary()<ParsedDocstring.summary>}).
   - Field extraction (L{split_fields()<ParsedDocstring.split_fields>}).
   - Index term extraction (L{index_terms()<ParsedDocstring.index_terms>}.

 The L{parse()} function provides a single interface to the
 C{epydoc.markup} package: it takes a docstring and the name of a
 markup language; delegates to the appropriate parser; and returns the
 parsed docstring (along with any errors or warnings that were
 generated).

 The C{ParsedDocstring} output generation methods (C{to_M{format}()})
 use a L{DocstringLinker} to link the docstring output with the rest of
 the documentation that epydoc generates.  C{DocstringLinker}s are
 currently responsible for translating two kinds of crossreference:
   - index terms (L{translate_indexterm()
     <DocstringLinker.translate_indexterm>}).
   - identifier crossreferences (L{translate_identifier_xref()
     <DocstringLinker.translate_identifier_xref>}).

 A parsed docstring's fields can be extracted using the
 L{ParsedDocstring.split_fields()} method.  This method divides a
 docstring into its main body and a list of L{Field}s, each of which
 encodes a single field.  The field's bodies are encoded as
 C{ParsedDocstring}s.

 Markup errors are represented using L{ParseError}s.  These exception
 classes record information about the cause, location, and severity of
 each error.

 @sort: parse, ParsedDocstring, Field, DocstringLinker
 @group Errors and Warnings: ParseError
 @group Utility Functions: parse_type_of
 @var SCRWIDTH: The default width with which text will be wrapped
       when formatting the output of the parser.
 @type SCRWIDTH: C{int}
 @var _parse_warnings: Used by L{_parse_warn}.
 """
 __docformat__ = 'epytext en'

 import re, types, sys
 from epydoc import log
 from epydoc.util import plaintext_to_html, plaintext_to_latex
 import epydoc
 from epydoc.compat import *

 ##################################################
 ## Contents
 ##################################################
 #
 # 1. parse() dispatcher
 # 2. ParsedDocstring abstract base class
 # 3. Field class
 # 4. Docstring Linker
 # 5. ParseError exceptions
 # 6. Misc helpers
 #

 ##################################################
 ## Dispatcher
 ##################################################

 _markup_language_registry = {
     'restructuredtext': 'epydoc.markup.restructuredtext',
     'epytext': 'epydoc.markup.epytext',
     'plaintext': 'epydoc.markup.plaintext',
     'javadoc': 'epydoc.markup.javadoc',
     }

 def register_markup_language(name, parse_function):
     """
     Register a new markup language named C{name}, which can be parsed
     by the function C{parse_function}.

     @param name: The name of the markup language.  C{name} should be a
     simple identifier, such as C{'epytext'} or C{'restructuredtext'}.
     Markup language names are case insensitive.

     @param parse_function: A function which can be used to parse the
         markup language, and returns a L{ParsedDocstring}.  It should
         have the following signature:

             >>> def parse(s, errors):
             ...     'returns a ParsedDocstring'

         Where:
             - C{s} is the string to parse.  (C{s} will be a unicode
               string.)
             - C{errors} is a list; any errors that are generated
               during docstring parsing should be appended to this
               list (as L{ParseError} objects).
     """
     _markup_language_registry[name.lower()] = parse_function

 MARKUP_LANGUAGES_USED = set()

 def parse(docstring, markup='plaintext', errors=None, **options):
     """
     Parse the given docstring, and use it to construct a
     C{ParsedDocstring}.  If any fatal C{ParseError}s are encountered
     while parsing the docstring, then the docstring will be rendered
     as plaintext, instead.

     @type docstring: C{string}
     @param docstring: The docstring to encode.
     @type markup: C{string}
     @param markup: The name of the markup language that is used by
         the docstring.  If the markup language is not supported, then
         the docstring will be treated as plaintext.  The markup name
         is case-insensitive.
     @param errors: A list where any errors generated during parsing
         will be stored.  If no list is specified, then fatal errors
         will generate exceptions, and non-fatal errors will be
         ignored.
     @type errors: C{list} of L{ParseError}
     @rtype: L{ParsedDocstring}
     @return: A L{ParsedDocstring} that encodes the contents of
         C{docstring}.
     @raise ParseError: If C{errors} is C{None} and an error is
         encountered while parsing.
     """
     # Initialize errors list.
     raise_on_error = (errors is None)
     if errors == None: errors = []

     # Normalize the markup language name.
     markup = markup.lower()

     # Is the markup language valid?
     if not re.match(r'\w+', markup):
         _parse_warn('Bad markup language name %r.  Treating '
                     'docstrings as plaintext.' % markup)
         import epydoc.markup.plaintext as plaintext
         return plaintext.parse_docstring(docstring, errors, **options)

     # Is the markup language supported?
     if markup not in _markup_language_registry:
         _parse_warn('Unsupported markup language %r.  Treating '
                     'docstrings as plaintext.' % markup)
         import epydoc.markup.plaintext as plaintext
         return plaintext.parse_docstring(docstring, errors, **options)

     # Get the parse function.
     parse_docstring = _markup_language_registry[markup]

     # If it's a string, then it names a function to import.
     if isinstance(parse_docstring, basestring):
         try: exec('from %s import parse_docstring' % parse_docstring)
         except ImportError, e:
             _parse_warn('Error importing %s for markup language %s: %s' %
                         (parse_docstring, markup, e))
             import epydoc.markup.plaintext as plaintext
             return plaintext.parse_docstring(docstring, errors, **options)
         _markup_language_registry[markup] = parse_docstring

     # Keep track of which markup languages have been used so far.
     MARKUP_LANGUAGES_USED.add(markup)

     # Parse the docstring.
     try: parsed_docstring = parse_docstring(docstring, errors, **options)
     except KeyboardInterrupt: raise
     except Exception, e:
         if epydoc.DEBUG: raise
         log.error('Internal error while parsing a docstring: %s; '
                   'treating docstring as plaintext' % e)
         import epydoc.markup.plaintext as plaintext
         return plaintext.parse_docstring(docstring, errors, **options)

     # Check for fatal errors.
     fatal_errors = [e for e in errors if e.is_fatal()]
     if fatal_errors and raise_on_error: raise fatal_errors[0]
     if fatal_errors:
         import epydoc.markup.plaintext as plaintext
         return plaintext.parse_docstring(docstring, errors, **options)

     return parsed_docstring

 # only issue each warning once:
 _parse_warnings = {}
 def _parse_warn(estr):
     """
     Print a warning message.  If the given error has already been
     printed, then do nothing.
     """
     global _parse_warnings
     if estr in _parse_warnings: return
     _parse_warnings[estr] = 1
     log.warning(estr)

 ##################################################
 ## ParsedDocstring
 ##################################################
 class ParsedDocstring:
     """
     A standard intermediate representation for parsed docstrings that
     can be used to generate output.  Parsed docstrings are produced by
     markup parsers (such as L{epytext.parse} or L{javadoc.parse}).
     C{ParsedDocstring}s support several kinds of operation:
       - output generation (L{to_plaintext()}, L{to_html()}, and
         L{to_latex()}).
       - Summarization (L{summary()}).
       - Field extraction (L{split_fields()}).
       - Index term extraction (L{index_terms()}.

     The output generation methods (C{to_M{format}()}) use a
     L{DocstringLinker} to link the docstring output with the rest
     of the documentation that epydoc generates.

     Subclassing
     ===========
     The only method that a subclass is I{required} to implement is
     L{to_plaintext()}; but it is often useful to override the other
     methods.  The default behavior of each method is described below:
       - C{to_I{format}}: Calls C{to_plaintext}, and uses the string it
         returns to generate verbatim output.
       - C{summary}: Returns C{self} (i.e., the entire docstring).
       - C{split_fields}: Returns C{(self, [])} (i.e., extracts no
         fields).
       - C{index_terms}: Returns C{[]} (i.e., extracts no index terms).

     If and when epydoc adds more output formats, new C{to_I{format}}
     methods will be added to this base class; but they will always
     be given a default implementation.
     """
     def split_fields(self, errors=None):
         """
         Split this docstring into its body and its fields.

         @return: A tuple C{(M{body}, M{fields})}, where C{M{body}} is
             the main body of this docstring, and C{M{fields}} is a list
             of its fields.  If the resulting body is empty, return
             C{None} for the body.
         @rtype: C{(L{ParsedDocstring}, list of L{Field})}
         @param errors: A list where any errors generated during
             splitting will be stored.  If no list is specified, then
             errors will be ignored.
         @type errors: C{list} of L{ParseError}
         """
         # Default behavior:
         return self, []

     def summary(self):
         """
         @return: A pair consisting of a short summary of this docstring and a
             boolean value indicating whether there is further documentation
             in addition to the summary. Typically, the summary consists of the
             first sentence of the docstring.
         @rtype: (L{ParsedDocstring}, C{bool})
         """
         # Default behavior:
         return self, False

     def concatenate(self, other):
         """
         @return: A new parsed docstring containing the concatination
             of this docstring and C{other}.
         @raise ValueError: If the two parsed docstrings are
             incompatible.
         """
         return ConcatenatedDocstring(self, other)

     def __add__(self, other): return self.concatenate(other)

     def to_html(self, docstring_linker, **options):
         """
         Translate this docstring to HTML.

         @param docstring_linker: An HTML translator for crossreference
             links into and out of the docstring.
         @type docstring_linker: L{DocstringLinker}
         @param options: Any extra options for the output.  Unknown
             options are ignored.
         @return: An HTML fragment that encodes this docstring.
         @rtype: C{string}
         """
         # Default behavior:
         plaintext = plaintext_to_html(self.to_plaintext(docstring_linker))
         return '<pre class="literalblock">\n%s\n</pre>\n' % plaintext

     def to_latex(self, docstring_linker, **options):
         """
         Translate this docstring to LaTeX.

         @param docstring_linker: A LaTeX translator for crossreference
             links into and out of the docstring.
         @type docstring_linker: L{DocstringLinker}
         @param options: Any extra options for the output.  Unknown
             options are ignored.
         @return: A LaTeX fragment that encodes this docstring.
         @rtype: C{string}
         """
         # Default behavior:
         plaintext = plaintext_to_latex(self.to_plaintext(docstring_linker))
         return '\\begin{alltt}\n%s\\end{alltt}\n\n' % plaintext

     def to_plaintext(self, docstring_linker, **options):
         """
         Translate this docstring to plaintext.

         @param docstring_linker: A plaintext translator for
             crossreference links into and out of the docstring.
         @type docstring_linker: L{DocstringLinker}
         @param options: Any extra options for the output.  Unknown
             options are ignored.
         @return: A plaintext fragment that encodes this docstring.
         @rtype: C{string}
         """
         raise NotImplementedError, 'ParsedDocstring.to_plaintext()'

     def index_terms(self):
         """
         @return: The list of index terms that are defined in this
             docstring.  Each of these items will be added to the index
             page of the documentation.
         @rtype: C{list} of C{ParsedDocstring}
         """
         # Default behavior:
         return []

 ##################################################
 ## Concatenated Docstring
 ##################################################
 class ConcatenatedDocstring:
     def __init__(self, *parsed_docstrings):
         self._parsed_docstrings = [pds for pds in parsed_docstrings
                                    if pds is not None]

     def split_fields(self, errors=None):
         bodies = []
         fields = []
         for doc in self._parsed_docstrings:
             b,f = doc.split_fields()
             bodies.append(b)
             fields.extend(f)

         return ConcatenatedDocstring(*bodies), fields

     def summary(self):
         return self._parsed_docstrings[0].summary()

     def to_html(self, docstring_linker, **options):
         htmlstring = ''
         for doc in self._parsed_docstrings:
             htmlstring += doc.to_html(docstring_linker, **options)
         return htmlstring

     def to_latex(self, docstring_linker, **options):
         latexstring = ''
         for doc in self._parsed_docstrings:
             latexstring += doc.to_latex(docstring_linker, **options)
         return latexstring

     def to_plaintext(self, docstring_linker, **options):
         textstring = ''
         for doc in self._parsed_docstrings:
             textstring += doc.to_plaintext(docstring_linker, **options)
         return textstring

     def index_terms(self):
         terms = []
         for doc in self._parsed_docstrings:
             terms += doc.index_terms()
         return terms

 ##################################################
 ## Fields
 ##################################################
 class Field:
     """
     The contents of a docstring's field.  Docstring fields are used
     to describe specific aspects of an object, such as a parameter of
     a function or the author of a module.  Each field consists of a
     tag, an optional argument, and a body:
       - The tag specifies the type of information that the field
         encodes.
       - The argument specifies the object that the field describes.
         The argument may be C{None} or a C{string}.
       - The body contains the field's information.

     Tags are automatically downcased and stripped; and arguments are
     automatically stripped.
     """
     def __init__(self, tag, arg, body):
         self._tag = tag.lower().strip()
         if arg is None: self._arg = None
         else: self._arg = arg.strip()
         self._body = body

     def tag(self):
         """
         @return: This field's tag.
         @rtype: C{string}
         """
         return self._tag

     def arg(self):
         """
         @return: This field's argument, or C{None} if this field has
             no argument.
         @rtype: C{string} or C{None}
         """
         return self._arg

     def body(self):
         """
         @return: This field's body.
         @rtype: L{ParsedDocstring}
         """
         return self._body

     def __repr__(self):
         if self._arg is None:
             return '<Field @%s: ...>' % self._tag
         else:
             return '<Field @%s %s: ...>' % (self._tag, self._arg)

 ##################################################
 ## Docstring Linker (resolves crossreferences)
 ##################################################
 class DocstringLinker:
     """
     A translator for crossreference links into and out of a
     C{ParsedDocstring}.  C{DocstringLinker} is used by
     C{ParsedDocstring} to convert these crossreference links into
     appropriate output formats.  For example,
     C{DocstringLinker.to_html} expects a C{DocstringLinker} that
     converts crossreference links to HTML.
     """
     def translate_indexterm(self, indexterm):
         """
         Translate an index term to the appropriate output format.  The
         output will typically include a crossreference anchor.

         @type indexterm: L{ParsedDocstring}
         @param indexterm: The index term to translate.
         @rtype: C{string}
         @return: The translated index term.
         """
         raise NotImplementedError, 'DocstringLinker.translate_indexterm()'

     def translate_identifier_xref(self, identifier, label=None):
         """
         Translate a crossreference link to a Python identifier to the
         appropriate output format.  The output will typically include
         a reference or pointer to the crossreference target.

         @type identifier: C{string}
         @param identifier: The name of the Python identifier that
             should be linked to.
         @type label: C{string} or C{None}
         @param label: The label that should be used for the identifier,
             if it's different from the name of the identifier.
         @rtype: C{string}
         @return: The translated crossreference link.
         """
         raise NotImplementedError, 'DocstringLinker.translate_xref()'

 ##################################################
 ## ParseError exceptions
 ##################################################

 class ParseError(Exception):
     """
     The base class for errors generated while parsing docstrings.

     @ivar _linenum: The line on which the error occured within the
         docstring.  The linenum of the first line is 0.
     @type _linenum: C{int}
     @ivar _offset: The line number where the docstring begins.  This
         offset is added to C{_linenum} when displaying the line number
         of the error.  Default value: 1.
     @type _offset: C{int}
     @ivar _descr: A description of the error.
     @type _descr: C{string}
     @ivar _fatal: True if this is a fatal error.
     @type _fatal: C{boolean}
     """
     def __init__(self, descr, linenum=None, is_fatal=1):
         """
         @type descr: C{string}
         @param descr: A description of the error.
         @type linenum: C{int}
         @param linenum: The line on which the error occured within
             the docstring.  The linenum of the first line is 0.
         @type is_fatal: C{boolean}
         @param is_fatal: True if this is a fatal error.
         """
         self._descr = descr
         self._linenum = linenum
         self._fatal = is_fatal
         self._offset = 1

     def is_fatal(self):
         """
         @return: true if this is a fatal error.  If an error is fatal,
             then epydoc should ignore the output of the parser, and
             parse the docstring as plaintext.
         @rtype: C{boolean}
         """
         return self._fatal

     def linenum(self):
         """
         @return: The line number on which the error occured (including
         any offset).  If the line number is unknown, then return
         C{None}.
         @rtype: C{int} or C{None}
         """
         if self._linenum is None: return None
         else: return self._offset + self._linenum

     def set_linenum_offset(self, offset):
         """
         Set the line number offset for this error.  This offset is the
         line number where the docstring begins.  This offset is added
         to C{_linenum} when displaying the line number of the error.

         @param offset: The new line number offset.
         @type offset: C{int}
         @rtype: C{None}
         """
         self._offset = offset

     def descr(self):
         return self._descr

     def __str__(self):
         """
         Return a string representation of this C{ParseError}.  This
         multi-line string contains a description of the error, and
         specifies where it occured.

         @return: the informal representation of this C{ParseError}.
         @rtype: C{string}
         """
         if self._linenum is not None:
             return 'Line %s: %s' % (self._linenum+self._offset, self.descr())
         else:
             return self.descr()

     def __repr__(self):
         """
         Return the formal representation of this C{ParseError}.
         C{ParseError}s have formal representations of the form::
            <ParseError on line 12>

         @return: the formal representation of this C{ParseError}.
         @rtype: C{string}
         """
         if self._linenum is None:
             return '<ParseError on line %d' % self._offset
         else:
             return '<ParseError on line %d>' % (self._linenum+self._offset)

     def __cmp__(self, other):
         """
         Compare two C{ParseError}s, based on their line number.
           - Return -1 if C{self.linenum<other.linenum}
           - Return +1 if C{self.linenum>other.linenum}
           - Return 0 if C{self.linenum==other.linenum}.
         The return value is undefined if C{other} is not a
         ParseError.

         @rtype: C{int}
         """
         if not isinstance(other, ParseError): return -1000
         return cmp(self._linenum+self._offset,
                    other._linenum+other._offset)

 ##################################################
 ## Misc helpers
 ##################################################
 # These are used by multiple markup parsers

 def parse_type_of(obj):
     """
     @return: A C{ParsedDocstring} that encodes the type of the given
     object.
     @rtype: L{ParsedDocstring}
     @param obj: The object whose type should be returned as DOM document.
     @type obj: any
     """
     # This is a bit hackish; oh well. :)
     from epydoc.markup.epytext import ParsedEpytextDocstring
     from xml.dom.minidom import Document
     doc = Document()
     epytext = doc.createElement('epytext')
     para = doc.createElement('para')
     doc.appendChild(epytext)
     epytext.appendChild(para)

     if type(obj) is types.InstanceType:
         link = doc.createElement('link')
         name = doc.createElement('name')
         target = doc.createElement('target')
         para.appendChild(link)
         link.appendChild(name)
         link.appendChild(target)
         name.appendChild(doc.createTextNode(str(obj.__class__.__name__)))
         target.appendChild(doc.createTextNode(str(obj.__class__)))
     else:
         code = doc.createElement('code')
         para.appendChild(code)
         code.appendChild(doc.createTextNode(type(obj).__name__))
     return ParsedEpytextDocstring(doc)
	#
	# epydoc package file
	#
	# A python documentation Module
	# Edward Loper
	#
	# $Id: __init__.py 1577 2007-03-09 23:26:21Z dvarrazzo $
	#

	"""
	Markup language support for docstrings. Each submodule defines a
	parser for a single markup language. These parsers convert an
	object's docstring to a L{ParsedDocstring}, a standard intermediate
	representation that can be used to generate output.
	C{ParsedDocstring}s support the following operations:
	- output generation (L{to_plaintext()<ParsedDocstring.to_plaintext>},
	L{to_html()<ParsedDocstring.to_html>}, and
	L{to_latex()<ParsedDocstring.to_latex>}).
	- Summarization (L{summary()<ParsedDocstring.summary>}).
	- Field extraction (L{split_fields()<ParsedDocstring.split_fields>}).
	- Index term extraction (L{index_terms()<ParsedDocstring.index_terms>}.

	The L{parse()} function provides a single interface to the
	C{epydoc.markup} package: it takes a docstring and the name of a
	markup language; delegates to the appropriate parser; and returns the
	parsed docstring (along with any errors or warnings that were
	generated).

	The C{ParsedDocstring} output generation methods (C{to_M{format}()})
	use a L{DocstringLinker} to link the docstring output with the rest of
	the documentation that epydoc generates. C{DocstringLinker}s are
	currently responsible for translating two kinds of crossreference:
	- index terms (L{translate_indexterm()
	<DocstringLinker.translate_indexterm>}).
	- identifier crossreferences (L{translate_identifier_xref()
	<DocstringLinker.translate_identifier_xref>}).

	A parsed docstring's fields can be extracted using the
	L{ParsedDocstring.split_fields()} method. This method divides a
	docstring into its main body and a list of L{Field}s, each of which
	encodes a single field. The field's bodies are encoded as
	C{ParsedDocstring}s.

	Markup errors are represented using L{ParseError}s. These exception
	classes record information about the cause, location, and severity of
	each error.

	@sort: parse, ParsedDocstring, Field, DocstringLinker
	@group Errors and Warnings: ParseError
	@group Utility Functions: parse_type_of
	@var SCRWIDTH: The default width with which text will be wrapped
	when formatting the output of the parser.
	@type SCRWIDTH: C{int}
	@var _parse_warnings: Used by L{_parse_warn}.
	"""
	__docformat__ = 'epytext en'

	import re, types, sys
	from epydoc import log
	from epydoc.util import plaintext_to_html, plaintext_to_latex
	import epydoc
	from epydoc.compat import *

	##################################################
	## Contents
	##################################################
	#
	# 1. parse() dispatcher
	# 2. ParsedDocstring abstract base class
	# 3. Field class
	# 4. Docstring Linker
	# 5. ParseError exceptions
	# 6. Misc helpers
	#

	##################################################
	## Dispatcher
	##################################################

	_markup_language_registry = {
	'restructuredtext': 'epydoc.markup.restructuredtext',
	'epytext': 'epydoc.markup.epytext',
	'plaintext': 'epydoc.markup.plaintext',
	'javadoc': 'epydoc.markup.javadoc',
	}

	def register_markup_language(name, parse_function):
	"""
	Register a new markup language named C{name}, which can be parsed
	by the function C{parse_function}.

	@param name: The name of the markup language. C{name} should be a
	simple identifier, such as C{'epytext'} or C{'restructuredtext'}.
	Markup language names are case insensitive.

	@param parse_function: A function which can be used to parse the
	markup language, and returns a L{ParsedDocstring}. It should
	have the following signature:

	>>> def parse(s, errors):
	... 'returns a ParsedDocstring'

	Where:
	- C{s} is the string to parse. (C{s} will be a unicode
	string.)
	- C{errors} is a list; any errors that are generated
	during docstring parsing should be appended to this
	list (as L{ParseError} objects).
	"""
	_markup_language_registry[name.lower()] = parse_function

	MARKUP_LANGUAGES_USED = set()

	def parse(docstring, markup='plaintext', errors=None, **options):
	"""
	Parse the given docstring, and use it to construct a
	C{ParsedDocstring}. If any fatal C{ParseError}s are encountered
	while parsing the docstring, then the docstring will be rendered
	as plaintext, instead.

	@type docstring: C{string}
	@param docstring: The docstring to encode.
	@type markup: C{string}
	@param markup: The name of the markup language that is used by
	the docstring. If the markup language is not supported, then
	the docstring will be treated as plaintext. The markup name
	is case-insensitive.
	@param errors: A list where any errors generated during parsing
	will be stored. If no list is specified, then fatal errors
	will generate exceptions, and non-fatal errors will be
	ignored.
	@type errors: C{list} of L{ParseError}
	@rtype: L{ParsedDocstring}
	@return: A L{ParsedDocstring} that encodes the contents of
	C{docstring}.
	@raise ParseError: If C{errors} is C{None} and an error is
	encountered while parsing.
	"""
	# Initialize errors list.
	raise_on_error = (errors is None)
	if errors == None: errors = []

	# Normalize the markup language name.
	markup = markup.lower()

	# Is the markup language valid?
	if not re.match(r'\w+', markup):
	_parse_warn('Bad markup language name %r. Treating '
	'docstrings as plaintext.' % markup)
	import epydoc.markup.plaintext as plaintext
	return plaintext.parse_docstring(docstring, errors, **options)

	# Is the markup language supported?
	if markup not in _markup_language_registry:
	_parse_warn('Unsupported markup language %r. Treating '
	'docstrings as plaintext.' % markup)
	import epydoc.markup.plaintext as plaintext
	return plaintext.parse_docstring(docstring, errors, **options)

	# Get the parse function.
	parse_docstring = _markup_language_registry[markup]

	# If it's a string, then it names a function to import.
	if isinstance(parse_docstring, basestring):
	try: exec('from %s import parse_docstring' % parse_docstring)
	except ImportError, e:
	_parse_warn('Error importing %s for markup language %s: %s' %
	(parse_docstring, markup, e))
	import epydoc.markup.plaintext as plaintext
	return plaintext.parse_docstring(docstring, errors, **options)
	_markup_language_registry[markup] = parse_docstring

	# Keep track of which markup languages have been used so far.
	MARKUP_LANGUAGES_USED.add(markup)

	# Parse the docstring.
	try: parsed_docstring = parse_docstring(docstring, errors, **options)
	except KeyboardInterrupt: raise
	except Exception, e:
	if epydoc.DEBUG: raise
	log.error('Internal error while parsing a docstring: %s; '
	'treating docstring as plaintext' % e)
	import epydoc.markup.plaintext as plaintext
	return plaintext.parse_docstring(docstring, errors, **options)

	# Check for fatal errors.
	fatal_errors = [e for e in errors if e.is_fatal()]
	if fatal_errors and raise_on_error: raise fatal_errors[0]
	if fatal_errors:
	import epydoc.markup.plaintext as plaintext
	return plaintext.parse_docstring(docstring, errors, **options)

	return parsed_docstring

	# only issue each warning once:
	_parse_warnings = {}
	def _parse_warn(estr):
	"""
	Print a warning message. If the given error has already been
	printed, then do nothing.
	"""
	global _parse_warnings
	if estr in _parse_warnings: return
	_parse_warnings[estr] = 1
	log.warning(estr)

	##################################################
	## ParsedDocstring
	##################################################
	class ParsedDocstring:
	"""
	A standard intermediate representation for parsed docstrings that
	can be used to generate output. Parsed docstrings are produced by
	markup parsers (such as L{epytext.parse} or L{javadoc.parse}).
	C{ParsedDocstring}s support several kinds of operation:
	- output generation (L{to_plaintext()}, L{to_html()}, and
	L{to_latex()}).
	- Summarization (L{summary()}).
	- Field extraction (L{split_fields()}).
	- Index term extraction (L{index_terms()}.

	The output generation methods (C{to_M{format}()}) use a
	L{DocstringLinker} to link the docstring output with the rest
	of the documentation that epydoc generates.

	Subclassing
	===========
	The only method that a subclass is I{required} to implement is
	L{to_plaintext()}; but it is often useful to override the other
	methods. The default behavior of each method is described below:
	- C{to_I{format}}: Calls C{to_plaintext}, and uses the string it
	returns to generate verbatim output.
	- C{summary}: Returns C{self} (i.e., the entire docstring).
	- C{split_fields}: Returns C{(self, [])} (i.e., extracts no
	fields).
	- C{index_terms}: Returns C{[]} (i.e., extracts no index terms).

	If and when epydoc adds more output formats, new C{to_I{format}}
	methods will be added to this base class; but they will always
	be given a default implementation.
	"""
	def split_fields(self, errors=None):
	"""
	Split this docstring into its body and its fields.

	@return: A tuple C{(M{body}, M{fields})}, where C{M{body}} is
	the main body of this docstring, and C{M{fields}} is a list
	of its fields. If the resulting body is empty, return
	C{None} for the body.
	@rtype: C{(L{ParsedDocstring}, list of L{Field})}
	@param errors: A list where any errors generated during
	splitting will be stored. If no list is specified, then
	errors will be ignored.
	@type errors: C{list} of L{ParseError}
	"""
	# Default behavior:
	return self, []

	def summary(self):
	"""
	@return: A pair consisting of a short summary of this docstring and a
	boolean value indicating whether there is further documentation
	in addition to the summary. Typically, the summary consists of the
	first sentence of the docstring.
	@rtype: (L{ParsedDocstring}, C{bool})
	"""
	# Default behavior:
	return self, False

	def concatenate(self, other):
	"""
	@return: A new parsed docstring containing the concatination
	of this docstring and C{other}.
	@raise ValueError: If the two parsed docstrings are
	incompatible.
	"""
	return ConcatenatedDocstring(self, other)

	def __add__(self, other): return self.concatenate(other)

	def to_html(self, docstring_linker, **options):
	"""
	Translate this docstring to HTML.

	@param docstring_linker: An HTML translator for crossreference
	links into and out of the docstring.
	@type docstring_linker: L{DocstringLinker}
	@param options: Any extra options for the output. Unknown
	options are ignored.
	@return: An HTML fragment that encodes this docstring.
	@rtype: C{string}
	"""
	# Default behavior:
	plaintext = plaintext_to_html(self.to_plaintext(docstring_linker))
	return '<pre class="literalblock">\n%s\n</pre>\n' % plaintext

	def to_latex(self, docstring_linker, **options):
	"""
	Translate this docstring to LaTeX.

	@param docstring_linker: A LaTeX translator for crossreference
	links into and out of the docstring.
	@type docstring_linker: L{DocstringLinker}
	@param options: Any extra options for the output. Unknown
	options are ignored.
	@return: A LaTeX fragment that encodes this docstring.
	@rtype: C{string}
	"""
	# Default behavior:
	plaintext = plaintext_to_latex(self.to_plaintext(docstring_linker))
	return '\\begin{alltt}\n%s\\end{alltt}\n\n' % plaintext

	def to_plaintext(self, docstring_linker, **options):
	"""
	Translate this docstring to plaintext.

	@param docstring_linker: A plaintext translator for
	crossreference links into and out of the docstring.
	@type docstring_linker: L{DocstringLinker}
	@param options: Any extra options for the output. Unknown
	options are ignored.
	@return: A plaintext fragment that encodes this docstring.
	@rtype: C{string}
	"""
	raise NotImplementedError, 'ParsedDocstring.to_plaintext()'

	def index_terms(self):
	"""
	@return: The list of index terms that are defined in this
	docstring. Each of these items will be added to the index
	page of the documentation.
	@rtype: C{list} of C{ParsedDocstring}
	"""
	# Default behavior:
	return []

	##################################################
	## Concatenated Docstring
	##################################################
	class ConcatenatedDocstring:
	def __init__(self, *parsed_docstrings):
	self._parsed_docstrings = [pds for pds in parsed_docstrings
	if pds is not None]

	def split_fields(self, errors=None):
	bodies = []
	fields = []
	for doc in self._parsed_docstrings:
	b,f = doc.split_fields()
	bodies.append(b)
	fields.extend(f)

	return ConcatenatedDocstring(*bodies), fields

	def summary(self):
	return self._parsed_docstrings[0].summary()

	def to_html(self, docstring_linker, **options):
	htmlstring = ''
	for doc in self._parsed_docstrings:
	htmlstring += doc.to_html(docstring_linker, **options)
	return htmlstring

	def to_latex(self, docstring_linker, **options):
	latexstring = ''
	for doc in self._parsed_docstrings:
	latexstring += doc.to_latex(docstring_linker, **options)
	return latexstring

	def to_plaintext(self, docstring_linker, **options):
	textstring = ''
	for doc in self._parsed_docstrings:
	textstring += doc.to_plaintext(docstring_linker, **options)
	return textstring

	def index_terms(self):
	terms = []
	for doc in self._parsed_docstrings:
	terms += doc.index_terms()
	return terms

	##################################################
	## Fields
	##################################################
	class Field:
	"""
	The contents of a docstring's field. Docstring fields are used
	to describe specific aspects of an object, such as a parameter of
	a function or the author of a module. Each field consists of a
	tag, an optional argument, and a body:
	- The tag specifies the type of information that the field
	encodes.
	- The argument specifies the object that the field describes.
	The argument may be C{None} or a C{string}.
	- The body contains the field's information.

	Tags are automatically downcased and stripped; and arguments are
	automatically stripped.
	"""
	def __init__(self, tag, arg, body):
	self._tag = tag.lower().strip()
	if arg is None: self._arg = None
	else: self._arg = arg.strip()
	self._body = body

	def tag(self):
	"""
	@return: This field's tag.
	@rtype: C{string}
	"""
	return self._tag

	def arg(self):
	"""
	@return: This field's argument, or C{None} if this field has
	no argument.
	@rtype: C{string} or C{None}
	"""
	return self._arg

	def body(self):
	"""
	@return: This field's body.
	@rtype: L{ParsedDocstring}
	"""
	return self._body

	def __repr__(self):
	if self._arg is None:
	return '<Field @%s: ...>' % self._tag
	else:
	return '<Field @%s %s: ...>' % (self._tag, self._arg)

	##################################################
	## Docstring Linker (resolves crossreferences)
	##################################################
	class DocstringLinker:
	"""
	A translator for crossreference links into and out of a
	C{ParsedDocstring}. C{DocstringLinker} is used by
	C{ParsedDocstring} to convert these crossreference links into
	appropriate output formats. For example,
	C{DocstringLinker.to_html} expects a C{DocstringLinker} that
	converts crossreference links to HTML.
	"""
	def translate_indexterm(self, indexterm):
	"""
	Translate an index term to the appropriate output format. The
	output will typically include a crossreference anchor.

	@type indexterm: L{ParsedDocstring}
	@param indexterm: The index term to translate.
	@rtype: C{string}
	@return: The translated index term.
	"""
	raise NotImplementedError, 'DocstringLinker.translate_indexterm()'

	def translate_identifier_xref(self, identifier, label=None):
	"""
	Translate a crossreference link to a Python identifier to the
	appropriate output format. The output will typically include
	a reference or pointer to the crossreference target.

	@type identifier: C{string}
	@param identifier: The name of the Python identifier that
	should be linked to.
	@type label: C{string} or C{None}
	@param label: The label that should be used for the identifier,
	if it's different from the name of the identifier.
	@rtype: C{string}
	@return: The translated crossreference link.
	"""
	raise NotImplementedError, 'DocstringLinker.translate_xref()'

	##################################################
	## ParseError exceptions
	##################################################

	class ParseError(Exception):
	"""
	The base class for errors generated while parsing docstrings.

	@ivar _linenum: The line on which the error occured within the
	docstring. The linenum of the first line is 0.
	@type _linenum: C{int}
	@ivar _offset: The line number where the docstring begins. This
	offset is added to C{_linenum} when displaying the line number
	of the error. Default value: 1.
	@type _offset: C{int}
	@ivar _descr: A description of the error.
	@type _descr: C{string}
	@ivar _fatal: True if this is a fatal error.
	@type _fatal: C{boolean}
	"""
	def __init__(self, descr, linenum=None, is_fatal=1):
	"""
	@type descr: C{string}
	@param descr: A description of the error.
	@type linenum: C{int}
	@param linenum: The line on which the error occured within
	the docstring. The linenum of the first line is 0.
	@type is_fatal: C{boolean}
	@param is_fatal: True if this is a fatal error.
	"""
	self._descr = descr
	self._linenum = linenum
	self._fatal = is_fatal
	self._offset = 1

	def is_fatal(self):
	"""
	@return: true if this is a fatal error. If an error is fatal,
	then epydoc should ignore the output of the parser, and
	parse the docstring as plaintext.
	@rtype: C{boolean}
	"""
	return self._fatal

	def linenum(self):
	"""
	@return: The line number on which the error occured (including
	any offset). If the line number is unknown, then return
	C{None}.
	@rtype: C{int} or C{None}
	"""
	if self._linenum is None: return None
	else: return self._offset + self._linenum

	def set_linenum_offset(self, offset):
	"""
	Set the line number offset for this error. This offset is the
	line number where the docstring begins. This offset is added
	to C{_linenum} when displaying the line number of the error.

	@param offset: The new line number offset.
	@type offset: C{int}
	@rtype: C{None}
	"""
	self._offset = offset

	def descr(self):
	return self._descr

	def __str__(self):
	"""
	Return a string representation of this C{ParseError}. This
	multi-line string contains a description of the error, and
	specifies where it occured.

	@return: the informal representation of this C{ParseError}.
	@rtype: C{string}
	"""
	if self._linenum is not None:
	return 'Line %s: %s' % (self._linenum+self._offset, self.descr())
	else:
	return self.descr()

	def __repr__(self):
	"""
	Return the formal representation of this C{ParseError}.
	C{ParseError}s have formal representations of the form::
	<ParseError on line 12>

	@return: the formal representation of this C{ParseError}.
	@rtype: C{string}
	"""
	if self._linenum is None:
	return '<ParseError on line %d' % self._offset
	else:
	return '<ParseError on line %d>' % (self._linenum+self._offset)

	def __cmp__(self, other):
	"""
	Compare two C{ParseError}s, based on their line number.
	- Return -1 if C{self.linenum<other.linenum}
	- Return +1 if C{self.linenum>other.linenum}
	- Return 0 if C{self.linenum==other.linenum}.
	The return value is undefined if C{other} is not a
	ParseError.

	@rtype: C{int}
	"""
	if not isinstance(other, ParseError): return -1000
	return cmp(self._linenum+self._offset,
	other._linenum+other._offset)

	##################################################
	## Misc helpers
	##################################################
	# These are used by multiple markup parsers

	def parse_type_of(obj):
	"""
	@return: A C{ParsedDocstring} that encodes the type of the given
	object.
	@rtype: L{ParsedDocstring}
	@param obj: The object whose type should be returned as DOM document.
	@type obj: any
	"""
	# This is a bit hackish; oh well. :)
	from epydoc.markup.epytext import ParsedEpytextDocstring
	from xml.dom.minidom import Document
	doc = Document()
	epytext = doc.createElement('epytext')
	para = doc.createElement('para')
	doc.appendChild(epytext)
	epytext.appendChild(para)

	if type(obj) is types.InstanceType:
	link = doc.createElement('link')
	name = doc.createElement('name')
	target = doc.createElement('target')
	para.appendChild(link)
	link.appendChild(name)
	link.appendChild(target)
	name.appendChild(doc.createTextNode(str(obj.__class__.__name__)))
	target.appendChild(doc.createTextNode(str(obj.__class__)))
	else:
	code = doc.createElement('code')
	para.appendChild(code)
	code.appendChild(doc.createTextNode(type(obj).__name__))
	return ParsedEpytextDocstring(doc)