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Support error raising on missing variables and partials #109

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Support error raising on missing variables and partials #109

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40 changes: 28 additions & 12 deletions chevron/renderer.py
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Original file line number Diff line number Diff line change
Expand Up @@ -28,6 +28,10 @@ def unicode(x, y):
string_type = basestring # noqa: F821 (This is defined in python2)


class UndefinedError(ValueError):
pass


#
# Helper functions
#
Expand All @@ -48,7 +52,7 @@ def _html_escape(string):
return string


def _get_key(key, scopes, warn, keep, def_ldel, def_rdel):
def _get_key(key, scopes, warn, keep, error, def_ldel, def_rdel):
"""Get a key from the current scope"""

# If the key is a dot
Expand Down Expand Up @@ -91,6 +95,9 @@ def _get_key(key, scopes, warn, keep, def_ldel, def_rdel):

# We couldn't find the key in any of the scopes

if error:
raise UndefinedError('Could not find key "%s"' % key)

if warn:
sys.stderr.write("Could not find key '%s'%s" % (key, linesep))

Expand All @@ -100,14 +107,17 @@ def _get_key(key, scopes, warn, keep, def_ldel, def_rdel):
return ''


def _get_partial(name, partials_dict, partials_path, partials_ext):
def _get_partial(name, partials_dict, partials_path, partials_ext, error):
"""Load a partial"""
try:
# Maybe the partial is in the dictionary
return partials_dict[name]
except KeyError:
# Don't try loading from the file system if the partials_path is None or empty
if partials_path is None or partials_path == '': return ''
if partials_path is None or partials_path == '':
if error:
raise UndefinedError('Could not find partial "%s"' % name)
return ''

# Nope...
try:
Expand All @@ -119,6 +129,8 @@ def _get_partial(name, partials_dict, partials_path, partials_ext):

except IOError:
# Alright I give up on you
if error:
raise UndefinedError('Could not find partial "%s"' % name)
return ''


Expand All @@ -130,7 +142,7 @@ def _get_partial(name, partials_dict, partials_path, partials_ext):

def render(template='', data={}, partials_path='.', partials_ext='mustache',
partials_dict={}, padding='', def_ldel='{{', def_rdel='}}',
scopes=None, warn=False, keep=False):
scopes=None, warn=False, keep=False, error=False):
"""Render a mustache template.

Renders a mustache template with a data scope and partial capability.
Expand Down Expand Up @@ -179,12 +191,16 @@ def render(template='', data={}, partials_path='.', partials_ext='mustache',

keep -- Keep unreplaced tags when a template substitution isn't found in the data

error -- Raise error when a template substituion isn't found (variable, no escape, partial)

Returns:

A string containing the rendered template.
"""

if warn + keep + error > 1:
raise ValueError('Only one of warn, keep or error can be True')

# If the template is a seqeuence but not derived from a string
if isinstance(template, Sequence) and \
not isinstance(template, string_type):
Expand Down Expand Up @@ -230,7 +246,7 @@ def render(template='', data={}, partials_path='.', partials_ext='mustache',
# If we're a variable tag
elif tag == 'variable':
# Add the html escaped key to the output
thing = _get_key(key, scopes, warn=warn, keep=keep, def_ldel=def_ldel, def_rdel=def_rdel)
thing = _get_key(key, scopes, warn=warn, keep=keep, error=error, def_ldel=def_ldel, def_rdel=def_rdel)
if thing is True and key == '.':
# if we've coerced into a boolean by accident
# (inverted tags do this)
Expand All @@ -243,15 +259,15 @@ def render(template='', data={}, partials_path='.', partials_ext='mustache',
# If we're a no html escape tag
elif tag == 'no escape':
# Just lookup the key and add it
thing = _get_key(key, scopes, warn=warn, keep=keep, def_ldel=def_ldel, def_rdel=def_rdel)
thing = _get_key(key, scopes, warn=warn, keep=keep, error=error, def_ldel=def_ldel, def_rdel=def_rdel)
if not isinstance(thing, unicode_type):
thing = unicode(str(thing), 'utf-8')
output += thing

# If we're a section tag
elif tag == 'section':
# Get the sections scope
scope = _get_key(key, scopes, warn=warn, keep=keep, def_ldel=def_ldel, def_rdel=def_rdel)
scope = _get_key(key, scopes, warn=warn, keep=keep, error=False, def_ldel=def_ldel, def_rdel=def_rdel)

# If the scope is a callable (as described in
# https://mustache.github.io/mustache.5.html)
Expand Down Expand Up @@ -292,7 +308,7 @@ def render(template='', data={}, partials_path='.', partials_ext='mustache',
padding=padding,
def_ldel=def_ldel, def_rdel=def_rdel,
scopes=data and [data]+scopes or scopes,
warn=warn, keep=keep))
warn=warn, keep=keep, error=error))

if python3:
output += rend
Expand Down Expand Up @@ -329,7 +345,7 @@ def render(template='', data={}, partials_path='.', partials_ext='mustache',
partials_ext=partials_ext,
partials_dict=partials_dict,
def_ldel=def_ldel, def_rdel=def_rdel,
warn=warn, keep=keep)
warn=warn, keep=keep, error=error)

if python3:
output += rend
Expand All @@ -343,14 +359,14 @@ def render(template='', data={}, partials_path='.', partials_ext='mustache',
# If we're an inverted section
elif tag == 'inverted section':
# Add the flipped scope to the scopes
scope = _get_key(key, scopes, warn=warn, keep=keep, def_ldel=def_ldel, def_rdel=def_rdel)
scope = _get_key(key, scopes, warn=warn, keep=keep, error=False, def_ldel=def_ldel, def_rdel=def_rdel)
scopes.insert(0, not scope)

# If we're a partial
elif tag == 'partial':
# Load the partial
partial = _get_partial(key, partials_dict,
partials_path, partials_ext)
partials_path, partials_ext, error=error)

# Find what to pad the partial with
left = output.rpartition('\n')[2]
Expand All @@ -364,7 +380,7 @@ def render(template='', data={}, partials_path='.', partials_ext='mustache',
partials_dict=partials_dict,
def_ldel=def_ldel, def_rdel=def_rdel,
padding=part_padding, scopes=scopes,
warn=warn, keep=keep)
warn=warn, keep=keep, error=error)

# If the partial was indented
if left.isspace():
Expand Down
70 changes: 70 additions & 0 deletions test_spec.py
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Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,9 @@
import chevron

import sys

from chevron.renderer import UndefinedError

if sys.version_info[0] == 3:
python3 = True
else: # python 2
Expand Down Expand Up @@ -552,6 +555,73 @@ def test_keep_from_partials(self):
expected = '1st {{ missing_key }} 3rd'
self.assertEqual(result, expected)

def test_error_bad_arguments(self):
args = {
'template': '{{ value }}',
'data': {'value': '123'},
}
for warn, keep, error in (
(True, True, False),
(True, False, True),
(False, True, True),
(True, True, True),
):
with self.assertRaisesRegex(
ValueError, 'Only one of warn, keep or error can be True',
):
chevron.render(warn=warn, keep=keep, error=error, **args)

def test_error_no_undefined(self):
args = {
'template': '{{ value }}',
'data': {'value': '123'},
'error': True,
}
self.assertEqual(chevron.render(**args), '123')

def test_error_undefined_variable(self):
with self.assertRaisesRegex(
UndefinedError, 'Could not find key "some.value"',
):
chevron.render(template='{{ some.value }}', data={}, error=True)

def test_error_undefined_no_escape(self):
with self.assertRaisesRegex(
UndefinedError, 'Could not find key "some.value"',
):
chevron.render(template='{{{ some.value }}}', data={}, error=True)

def test_error_undefined_partial_dict(self):
with self.assertRaisesRegex(
UndefinedError, 'Could not find partial "some.value"',
):
chevron.render(
template='{{> some.value }}', data={}, error=True,
partials_dict={'other': 'value'},
)

def test_error_undefined_partial_fs(self):
with self.assertRaisesRegex(
UndefinedError, 'Could not find partial "some.value"',
):
chevron.render(
template='{{> some.value }}', data={}, error=True,
partials_dict={'other': 'value'},
partials_path='inexistent_path',
)

def test_error_undefined_section(self):
rendered = chevron.render(
template='{{#section}}123{{/section}}', data={}, error=True,
)
self.assertEqual(rendered, '')

def test_error_undefined_inverted_section(self):
rendered = chevron.render(
template='{{^section}}123{{/section}}', data={}, error=True,
)
self.assertEqual(rendered, '123')


# Run unit tests from command line
if __name__ == "__main__":
Expand Down