"""
This is the Django template system.
How it works:
The tokenize() function converts a template string (i.e., a string containing
markup with custom template tags) to tokens, which can be either plain text
(TOKEN_TEXT), variables (TOKEN_VAR) or block statements (TOKEN_BLOCK).
The Parser() class takes a list of tokens in its constructor, and its parse()
method returns a compiled template -- which is, under the hood, a list of
Node objects.
Each Node is responsible for creating some sort of output -- e.g. simple text
(TextNode), variable values in a given context (VariableNode), results of basic
logic (IfNode), results of looping (ForNode), or anything else. The core Node
types are TextNode, VariableNode, IfNode and ForNode, but plugin modules can
define their own custom node types.
Each Node has a render() method, which takes a Context and returns a string of
the rendered node. For example, the render() method of a Variable Node returns
the variable's value as a string. The render() method of an IfNode returns the
rendered output of whatever was inside the loop, recursively.
The Template class is a convenient wrapper that takes care of template
compilation and rendering.
Usage:
The only thing you should ever use directly in this file is the Template class.
Create a compiled template object with a template_string, then call render()
with a context. In the compilation stage, the TemplateSyntaxError exception
will be raised if the template doesn't have proper syntax.
Sample code:
>>> import template
>>> s = '''
...
... {% if test %}
... {{ varvalue }}
... {% endif %}
...
... '''
>>> t = template.Template(s)
(t is now a compiled template, and its render() method can be called multiple
times with multiple contexts)
>>> c = template.Context({'test':True, 'varvalue': 'Hello'})
>>> t.render(c)
'\n\n\n Hello
\n\n\n'
>>> c = template.Context({'test':False, 'varvalue': 'Hello'})
>>> t.render(c)
'\n\n\n\n'
"""
import re
from django.conf.settings import DEFAULT_CHARSET, TEMPLATE_DEBUG
__all__ = ('Template','Context','compile_string')
TOKEN_TEXT = 0
TOKEN_VAR = 1
TOKEN_BLOCK = 2
# template syntax constants
FILTER_SEPARATOR = '|'
FILTER_ARGUMENT_SEPARATOR = ':'
VARIABLE_ATTRIBUTE_SEPARATOR = '.'
BLOCK_TAG_START = '{%'
BLOCK_TAG_END = '%}'
VARIABLE_TAG_START = '{{'
VARIABLE_TAG_END = '}}'
ALLOWED_VARIABLE_CHARS = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_.'
# what to report as the origin for templates that come from non-loader sources
# (e.g. strings)
UNKNOWN_SOURCE=""
# match a variable or block tag and capture the entire tag, including start/end delimiters
tag_re = re.compile('(%s.*?%s|%s.*?%s)' % (re.escape(BLOCK_TAG_START), re.escape(BLOCK_TAG_END),
re.escape(VARIABLE_TAG_START), re.escape(VARIABLE_TAG_END)))
# global dict used by register_tag; maps custom tags to callback functions
registered_tags = {}
# global dict used by register_filter; maps custom filters to callback functions
registered_filters = {}
class TemplateSyntaxError(Exception):
pass
class ContextPopException(Exception):
"pop() has been called more times than push()"
pass
class TemplateDoesNotExist(Exception):
pass
class VariableDoesNotExist(Exception):
pass
class SilentVariableFailure(Exception):
"Any function raising this exception will be ignored by resolve_variable"
pass
class Origin(object):
def __init__(self, name):
self.name = name
def reload(self):
raise NotImplementedException
def __str__(self):
return self.name
class StringOrigin(Origin):
def __init__(self, source):
super(StringOrigin, self).__init__(UNKNOWN_SOURCE)
self.source = source
def reload(self):
return self.source
class Template:
def __init__(self, template_string, origin=None):
"Compilation stage"
if TEMPLATE_DEBUG and origin == None:
origin = StringOrigin(template_string)
# Could do some crazy stack-frame stuff to record where this string
# came from...
self.nodelist = compile_string(template_string, origin)
def __iter__(self):
for node in self.nodelist:
for subnode in node:
yield subnode
def render(self, context):
"Display stage -- can be called many times"
return self.nodelist.render(context)
def compile_string(template_string, origin):
"Compiles template_string into NodeList ready for rendering"
lexer = lexer_factory(template_string, origin)
parser = parser_factory(lexer.tokenize())
return parser.parse()
class Context:
"A stack container for variable context"
def __init__(self, dict=None):
dict = dict or {}
self.dicts = [dict]
def __repr__(self):
return repr(self.dicts)
def __iter__(self):
for d in self.dicts:
yield d
def push(self):
self.dicts = [{}] + self.dicts
def pop(self):
if len(self.dicts) == 1:
raise ContextPopException
del self.dicts[0]
def __setitem__(self, key, value):
"Set a variable in the current context"
self.dicts[0][key] = value
def __getitem__(self, key):
"Get a variable's value, starting at the current context and going upward"
for dict in self.dicts:
if dict.has_key(key):
return dict[key]
return ''
def __delitem__(self, key):
"Delete a variable from the current context"
del self.dicts[0][key]
def has_key(self, key):
for dict in self.dicts:
if dict.has_key(key):
return True
return False
def get(self, key, otherwise):
for dict in self.dicts:
if dict.has_key(key):
return dict[key]
return otherwise
def update(self, other_dict):
"Like dict.update(). Pushes an entire dictionary's keys and values onto the context."
self.dicts = [other_dict] + self.dicts
class Token:
def __init__(self, token_type, contents):
"The token_type must be TOKEN_TEXT, TOKEN_VAR or TOKEN_BLOCK"
self.token_type, self.contents = token_type, contents
def __str__(self):
return '<%s token: "%s...">' % (
{TOKEN_TEXT: 'Text', TOKEN_VAR: 'Var', TOKEN_BLOCK: 'Block'}[self.token_type],
self.contents[:20].replace('\n', '')
)
def __repr__(self):
return '<%s token: "%s">' % (
{TOKEN_TEXT: 'Text', TOKEN_VAR: 'Var', TOKEN_BLOCK: 'Block'}[self.token_type],
self.contents[:].replace('\n', '')
)
class Lexer(object):
def __init__(self, template_string, origin):
self.template_string = template_string
self.origin = origin
def tokenize(self):
"Return a list of tokens from a given template_string"
# remove all empty strings, because the regex has a tendency to add them
bits = filter(None, tag_re.split(self.template_string))
return map(self.create_token, bits)
def create_token(self,token_string):
"Convert the given token string into a new Token object and return it"
if token_string.startswith(VARIABLE_TAG_START):
token = Token(TOKEN_VAR, token_string[len(VARIABLE_TAG_START):-len(VARIABLE_TAG_END)].strip())
elif token_string.startswith(BLOCK_TAG_START):
token = Token(TOKEN_BLOCK, token_string[len(BLOCK_TAG_START):-len(BLOCK_TAG_END)].strip())
else:
token = Token(TOKEN_TEXT, token_string)
return token
class DebugLexer(Lexer):
def __init__(self, template_string, origin):
super(DebugLexer, self).__init__(template_string, origin)
def tokenize(self):
"Return a list of tokens from a given template_string"
token_tups, upto = [], 0
for match in tag_re.finditer(self.template_string):
start, end = match.span()
if start > upto:
token_tups.append( (self.template_string[upto:start], (upto, start)) )
upto = start
token_tups.append( (self.template_string[start:end], (start,end)) )
upto = end
last_bit = self.template_string[upto:]
if last_bit:
token_tups.append( (last_bit, (upto, upto + len(last_bit))) )
return [self.create_token(tok, (self.origin, loc)) for tok, loc in token_tups]
def create_token(self, token_string, source):
token = super(DebugLexer, self).create_token(token_string)
token.source = source
return token
class Parser(object):
def __init__(self, tokens):
self.tokens = tokens
def parse(self, parse_until=[]):
nodelist = self.create_nodelist()
while self.tokens:
token = self.next_token()
if token.token_type == TOKEN_TEXT:
self.extend_nodelist(nodelist, TextNode(token.contents), token)
elif token.token_type == TOKEN_VAR:
if not token.contents:
self.empty_variable(token)
var_node = self.create_variable_node(token.contents)
self.extend_nodelist(nodelist, var_node,token)
elif token.token_type == TOKEN_BLOCK:
if token.contents in parse_until:
# put token back on token list so calling code knows why it terminated
self.prepend_token(token)
return nodelist
try:
command = token.contents.split()[0]
except IndexError:
self.empty_block_tag(token)
# execute callback function for this tag and append resulting node
self.enter_command(command, token)
try:
compile_func = registered_tags[command]
except KeyError:
self.invalid_block_tag(token, command)
try:
compiled_result = compile_func(self, token)
except TemplateSyntaxError, e:
if not self.compile_function_error(token, e):
raise
self.extend_nodelist(nodelist, compiled_result, token)
self.exit_command()
if parse_until:
self.unclosed_block_tag(parse_until)
return nodelist
def create_variable_node(self, contents):
return VariableNode(contents)
def create_nodelist(self):
return NodeList()
def extend_nodelist(self, nodelist, node, token):
nodelist.append(node)
def enter_command(self, command, token):
pass
def exit_command(self):
pass
def error(self, token, msg ):
return TemplateSyntaxError(msg)
def empty_variable(self, token):
raise self.error( token, "Empty variable tag")
def empty_block_tag(self, token):
raise self.error( token, "Empty block tag")
def invalid_block_tag(self, token, command):
raise self.error( token, "Invalid block tag: '%s'" % command)
def unclosed_block_tag(self, parse_until):
raise self.error(None, "Unclosed tags: %s " % ', '.join(parse_until))
def compile_function_error(self, token, e):
pass
def next_token(self):
return self.tokens.pop(0)
def prepend_token(self, token):
self.tokens.insert(0, token)
def delete_first_token(self):
del self.tokens[0]
class DebugParser(Parser):
def __init__(self, lexer):
super(DebugParser, self).__init__(lexer)
self.command_stack = []
def enter_command(self, command, token):
self.command_stack.append( (command, token.source) )
def exit_command(self):
self.command_stack.pop()
def error(self, token, msg):
return self.source_error(token.source, msg)
def source_error(self, source,msg):
e = TemplateSyntaxError(msg)
e.source = source
return e
def create_nodelist(self):
return DebugNodeList()
def create_variable_node(self, contents):
return DebugVariableNode(contents)
def extend_nodelist(self, nodelist, node, token):
node.source = token.source
super(DebugParser, self).extend_nodelist(nodelist, node, token)
def unclosed_block_tag(self, parse_until):
(command, source) = self.command_stack.pop()
msg = "Unclosed tag '%s'. Looking for one of: %s " % (command, ', '.join(parse_until))
raise self.source_error( source, msg)
def compile_function_error(self, token, e):
if not hasattr(e, 'source'):
e.source = token.source
if TEMPLATE_DEBUG:
lexer_factory = DebugLexer
parser_factory = DebugParser
else:
lexer_factory = Lexer
parser_factory = Parser
class TokenParser:
"""
Subclass this and implement the top() method to parse a template line. When
instantiating the parser, pass in the line from the Django template parser.
The parser's "tagname" instance-variable stores the name of the tag that
the filter was called with.
"""
def __init__(self, subject):
self.subject = subject
self.pointer = 0
self.backout = []
self.tagname = self.tag()
def top(self):
"Overload this method to do the actual parsing and return the result."
raise NotImplemented
def more(self):
"Returns True if there is more stuff in the tag."
return self.pointer < len(self.subject)
def back(self):
"Undoes the last microparser. Use this for lookahead and backtracking."
if not len(self.backout):
raise TemplateSyntaxError, "back called without some previous parsing"
self.pointer = self.backout.pop()
def tag(self):
"A microparser that just returns the next tag from the line."
subject = self.subject
i = self.pointer
if i >= len(subject):
raise TemplateSyntaxError, "expected another tag, found end of string: %s" % subject
p = i
while i < len(subject) and subject[i] not in (' ', '\t'):
i += 1
s = subject[p:i]
while i < len(subject) and subject[i] in (' ', '\t'):
i += 1
self.backout.append(self.pointer)
self.pointer = i
return s
def value(self):
"A microparser that parses for a value: some string constant or variable name."
subject = self.subject
i = self.pointer
if i >= len(subject):
raise TemplateSyntaxError, "Searching for value. Expected another value but found end of string: %s" % subject
if subject[i] in ('"', "'"):
p = i
i += 1
while i < len(subject) and subject[i] != subject[p]:
i += 1
if i >= len(subject):
raise TemplateSyntaxError, "Searching for value. Unexpected end of string in column %d: %s" % subject
i += 1
res = subject[p:i]
while i < len(subject) and subject[i] in (' ', '\t'):
i += 1
self.backout.append(self.pointer)
self.pointer = i
return res
else:
p = i
while i < len(subject) and subject[i] not in (' ', '\t'):
if subject[i] in ('"', "'"):
c = subject[i]
i += 1
while i < len(subject) and subject[i] != c:
i += 1
if i >= len(subject):
raise TemplateSyntaxError, "Searching for value. Unexpected end of string in column %d: %s" % subject
i += 1
s = subject[p:i]
while i < len(subject) and subject[i] in (' ', '\t'):
i += 1
self.backout.append(self.pointer)
self.pointer = i
return s
filter_raw_string = r"""
^%(i18n_open)s"(?P%(str)s)"%(i18n_close)s|
^"(?P%(str)s)"|
^(?P[%(var_chars)s]+)|
(?:%(filter_sep)s
(?P\w+)
(?:%(arg_sep)s
(?:
%(i18n_open)s"(?P%(str)s)"%(i18n_close)s|
"(?P%(str)s)"
)
)?
)""" % {
'str': r"""[^"\\]*(?:\\.[^"\\]*)*""",
'var_chars': "A-Za-z0-9\_\." ,
'filter_sep': re.escape(FILTER_SEPARATOR),
'arg_sep': re.escape(FILTER_ARGUMENT_SEPARATOR),
'i18n_open' : re.escape("_("),
'i18n_close' : re.escape(")"),
}
filter_raw_string = filter_raw_string.replace("\n", "").replace(" ", "")
filter_re = re.compile(filter_raw_string)
class FilterParser(object):
"""
Parses a variable token and its optional filters (all as a single string),
and return a list of tuples of the filter name and arguments.
Sample:
>>> token = 'variable|default:"Default value"|date:"Y-m-d"'
>>> p = FilterParser(token)
>>> p.filters
[('default', 'Default value'), ('date', 'Y-m-d')]
>>> p.var
'variable'
This class should never be instantiated outside of the
get_filters_from_token helper function.
"""
def __init__(self, token):
matches = filter_re.finditer(token)
var = None
filters = []
upto = 0
for match in matches:
start = match.start()
if upto != start:
raise TemplateSyntaxError, "Could not parse some characters: %s|%s|%s" % \
(token[:upto], token[upto:start], token[start:])
if var == None:
var, constant, i18n_constant = match.group("var", "constant", "i18n_constant")
if i18n_constant:
var = '"%s"' % _(i18n_constant)
elif constant:
var = '"%s"' % constant
upto = match.end()
if var == None:
raise TemplateSyntaxError, "Could not find variable at start of %s" % token
elif var.find(VARIABLE_ATTRIBUTE_SEPARATOR + '_') > -1 or var[0] == '_':
raise TemplateSyntaxError, "Variables and attributes may not begin with underscores: '%s'" % var
else:
filter_name = match.group("filter_name")
arg, i18n_arg = match.group("arg","i18n_arg")
if i18n_arg:
arg =_(i18n_arg.replace('\\', ''))
if arg:
arg = arg.replace('\\', '')
if not registered_filters.has_key(filter_name):
raise TemplateSyntaxError, "Invalid filter: '%s'" % filter_name
if registered_filters[filter_name][1] == True and arg is None:
raise TemplateSyntaxError, "Filter '%s' requires an argument" % filter_name
if registered_filters[filter_name][1] == False and arg is not None:
raise TemplateSyntaxError, "Filter '%s' should not have an argument (argument is %r)" % (filter_name, arg)
filters.append( (filter_name,arg) )
upto = match.end()
if upto != len(token):
raise TemplateSyntaxError, "Could not parse the remainder: %s" % token[upto:]
self.var , self.filters = var, filters
def get_filters_from_token(token):
"Convenient wrapper for FilterParser"
p = FilterParser(token)
return (p.var, p.filters)
def resolve_variable(path, context):
"""
Returns the resolved variable, which may contain attribute syntax, within
the given context. The variable may be a hard-coded string (if it begins
and ends with single or double quote marks).
>>> c = {'article': {'section':'News'}}
>>> resolve_variable('article.section', c)
'News'
>>> resolve_variable('article', c)
{'section': 'News'}
>>> class AClass: pass
>>> c = AClass()
>>> c.article = AClass()
>>> c.article.section = 'News'
>>> resolve_variable('article.section', c)
'News'
(The example assumes VARIABLE_ATTRIBUTE_SEPARATOR is '.')
"""
if path[0] in ('"', "'") and path[0] == path[-1]:
current = path[1:-1]
else:
current = context
bits = path.split(VARIABLE_ATTRIBUTE_SEPARATOR)
while bits:
try: # dictionary lookup
current = current[bits[0]]
except (TypeError, AttributeError, KeyError):
try: # attribute lookup
current = getattr(current, bits[0])
if callable(current):
if getattr(current, 'alters_data', False):
current = ''
else:
try: # method call (assuming no args required)
current = current()
except SilentVariableFailure:
current = ''
except TypeError: # arguments *were* required
current = '' # invalid method call
except (TypeError, AttributeError):
try: # list-index lookup
current = current[int(bits[0])]
except (IndexError, ValueError, KeyError):
raise VariableDoesNotExist, "Failed lookup for key [%s] in %r" % (bits[0], current) # missing attribute
del bits[0]
return current
def resolve_variable_with_filters(var_string, context):
"""
var_string is a full variable expression with optional filters, like:
a.b.c|lower|date:"y/m/d"
This function resolves the variable in the context, applies all filters and
returns the object.
"""
var, filters = get_filters_from_token(var_string)
try:
obj = resolve_variable(var, context)
except VariableDoesNotExist:
obj = ''
for name, arg in filters:
obj = registered_filters[name][0](obj, arg)
return obj
class Node:
def render(self, context):
"Return the node rendered as a string"
pass
def __iter__(self):
yield self
def get_nodes_by_type(self, nodetype):
"Return a list of all nodes (within this node and its nodelist) of the given type"
nodes = []
if isinstance(self, nodetype):
nodes.append(self)
if hasattr(self, 'nodelist'):
nodes.extend(self.nodelist.get_nodes_by_type(nodetype))
return nodes
class NodeList(list):
def render(self, context):
bits = []
for node in self:
if isinstance(node, Node):
bits.append(self.render_node(node, context))
else:
bits.append(node)
return ''.join(bits)
def get_nodes_by_type(self, nodetype):
"Return a list of all nodes of the given type"
nodes = []
for node in self:
nodes.extend(node.get_nodes_by_type(nodetype))
return nodes
def render_node(self, node, context):
return(node.render(context))
class DebugNodeList(NodeList):
def render_node(self, node, context):
try:
result = node.render(context)
except TemplateSyntaxError, e:
if not hasattr(e, 'source'):
e.source = node.source
raise
except Exception:
from sys import exc_info
wrapped = TemplateSyntaxError('Caught an exception while rendering.')
wrapped.source = node.source
wrapped.exc_info = exc_info()
raise wrapped
return result
class TextNode(Node):
def __init__(self, s):
self.s = s
def __repr__(self):
return "" % self.s[:25]
def render(self, context):
return self.s
class VariableNode(Node):
def __init__(self, var_string):
self.var_string = var_string
def __repr__(self):
return "" % self.var_string
def encode_output(self, output):
# Check type so that we don't run str() on a Unicode object
if not isinstance(output, basestring):
return str(output)
elif isinstance(output, unicode):
return output.encode(DEFAULT_CHARSET)
else:
return output
def render(self, context):
output = resolve_variable_with_filters(self.var_string, context)
return self.encode_output(output)
class DebugVariableNode(VariableNode):
def render(self, context):
try:
output = resolve_variable_with_filters(self.var_string, context)
except TemplateSyntaxError, e:
if not hasattr(e, 'source'):
e.source = self.source
raise
return self.encode_output(output)
def register_tag(token_command, callback_function):
registered_tags[token_command] = callback_function
def unregister_tag(token_command):
del registered_tags[token_command]
def register_filter(filter_name, callback_function, has_arg):
registered_filters[filter_name] = (callback_function, has_arg)
def unregister_filter(filter_name):
del registered_filters[filter_name]
import defaulttags
import defaultfilters