Xion/jinja_capture.py

## jinja_capture.py
from jinja2.ext import Extension
from jinja2.nodes import CallBlock, Output, MarkSafe

class CaptureExtension(Extension):
    ''' Generic capture extension, useful for providing
    content that should go into specific places in HTML template,
    such as the <head> tag for JavaScript includes.

    Syntax for providing content for so-called 'dataset' (here it's "js"):

    {% store 'foo' in 'js' %}
        <script ... >
    {% endstore %}

    and for emitting it:

    {% emit 'js' %}

    Extension inspired heavily by http://stackoverflow.com/a/6090560/434799 ,
    but improved and refined somewhat.
    '''
    tags = set(['store', 'emit'])

    def __init__(self, environment):
        super(CaptureExtension, self).__init__(environment)
        environment.extend(captured = {})

    def parse(self, parser):
        ''' Parsing function. Recognizes tags and produces
        appropriate nodes.
        '''
        tag = parser.stream.next()
        parse_method = getattr(self, '_parse_%s_tag' % tag.value)
        return parse_method(parser, tag)

    def _parse_store_tag(self, parser, tag):
        ''' Parses the {% store %} tag.
        @return: A template node for the tag
        '''
        key = parser.parse_tuple(simplified = True, extra_end_rules = ['name:in'])
        parser.stream.skip()    # skipping 'in'
        dataset = parser.parse_expression()
        body = parser.parse_statements(['name:end' + tag.value], drop_needle = True)

        node = CallBlock(self.call_method('_exec_store', [key, dataset]), [], [], body)
        node.set_lineno(tag.lineno) # for debugging
        return node

    def _parse_emit_tag(self, parser, tag):
        ''' Parses the {% emit %} tag.
        @return: A template node for the tag
        '''
        dataset = parser.parse_expression()
        emit_call_node = self.call_method('_exec_emit', [dataset], lineno = tag.lineno)
        nodes = [MarkSafe(emit_call_node)]
        return Output(nodes)

    def _exec_store(self, key, dataset, caller):
        ''' Executes the {% store %} command.
        @return: Empty string (this tag does not produce output)
        '''
        dataset_content = self.environment.captured.setdefault(dataset, {})
        if key not in dataset_content:
            dataset_content[key] = caller()
        return ""

    def _exec_emit(self, dataset):
        ''' Executes the {% emit %} command.
        @return: Content of specified dataset as string
        '''
        dataset_content = self.environment.captured.get(dataset, {})
        output = "\n".join(dataset_content.itervalues())
        return output
	from jinja2.ext import Extension
	from jinja2.nodes import CallBlock, Output, MarkSafe

	class CaptureExtension(Extension):
	''' Generic capture extension, useful for providing
	content that should go into specific places in HTML template,
	such as the <head> tag for JavaScript includes.

	Syntax for providing content for so-called 'dataset' (here it's "js"):

	{% store 'foo' in 'js' %}
	<script ... >
	{% endstore %}

	and for emitting it:

	{% emit 'js' %}

	Extension inspired heavily by http://stackoverflow.com/a/6090560/434799 ,
	but improved and refined somewhat.
	'''
	tags = set(['store', 'emit'])

	def __init__(self, environment):
	super(CaptureExtension, self).__init__(environment)
	environment.extend(captured = {})

	def parse(self, parser):
	''' Parsing function. Recognizes tags and produces
	appropriate nodes.
	'''
	tag = parser.stream.next()
	parse_method = getattr(self, '_parse_%s_tag' % tag.value)
	return parse_method(parser, tag)

	def _parse_store_tag(self, parser, tag):
	''' Parses the {% store %} tag.
	@return: A template node for the tag
	'''
	key = parser.parse_tuple(simplified = True, extra_end_rules = ['name:in'])
	parser.stream.skip() # skipping 'in'
	dataset = parser.parse_expression()
	body = parser.parse_statements(['name:end' + tag.value], drop_needle = True)

	node = CallBlock(self.call_method('_exec_store', [key, dataset]), [], [], body)
	node.set_lineno(tag.lineno) # for debugging
	return node

	def _parse_emit_tag(self, parser, tag):
	''' Parses the {% emit %} tag.
	@return: A template node for the tag
	'''
	dataset = parser.parse_expression()
	emit_call_node = self.call_method('_exec_emit', [dataset], lineno = tag.lineno)
	nodes = [MarkSafe(emit_call_node)]
	return Output(nodes)

	def _exec_store(self, key, dataset, caller):
	''' Executes the {% store %} command.
	@return: Empty string (this tag does not produce output)
	'''
	dataset_content = self.environment.captured.setdefault(dataset, {})
	if key not in dataset_content:
	dataset_content[key] = caller()
	return ""

	def _exec_emit(self, dataset):
	''' Executes the {% emit %} command.
	@return: Content of specified dataset as string
	'''
	dataset_content = self.environment.captured.get(dataset, {})
	output = "\n".join(dataset_content.itervalues())
	return output