Example of instrumenting jinja2 to trace template components

template_tracing.py

import contextlib
@contextlib.contextmanager
def trace_to_stderr(name):
    """Trivial proof-of-concept for tracing template rendering"""
    print >>sys.stderr, 'ENTER: %s' % (name,)
    yield
    print >>sys.stderr, 'EXIT: %s' % (name,)

class trace_decorator(object):
    def __init__(self, contextmgr_type, item_type, item_name, *args, **kwargs):
        self.contextmgr_type = contextmgr_type
        self.args = (item_name, item_type) + args
        self.kwargs = kwargs
    def __call__(self, function):
        @functools.wraps(function)
        def wrapped(*args, **kwargs):
            name = 'jinja2.%s' % ('.'.join((n.replace('.','_').replace('/','_') for n in self.args)))
            with self.contextmgr_type(name):
                return function(*args, **kwargs)
        return wrapped

import os
if os.environ.get('ENABLE_TRACELYTICS'):
    import oboe
    trace_method = oboe.Context.profile_block
else:
    trace_method = trace_to_stderr

block_decorator = functools.partial(trace_decorator, trace_method, 'block')
macro_decorator = functools.partial(trace_decorator, trace_method, 'macro')
macro_call_decorator = functools.partial(trace_decorator, trace_method, 'macro_call')

class TracedEnvironment(jinja2.Environment):
    def __init__(self, **options):
        if os.environ.get('ENABLE_TRACELYTICS'):
            self.block_decorator = '%s.block_decorator' % __name__
            self.macro_decorator = '%s.macro_decorator' % __name__
            self.macro_call_decorator = '%s.macro_call_decorator' % __name__
        jinja2.Environment.__init__(self, **options)

I can't get this to work with latest jinja2. I tried adapting it (I did figure out how it works...), but jinja2 doesn't seem to have a place to add the context objects.

I'll watch here to see if anyone else can get jinja2 tracing to work.