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import functools
import re
from importlib import import_module
from django.core.exceptions import ViewDoesNotExist
from django.utils.module_loading import module_has_submodule
from django.utils.regex_helper import _lazy_re_compile
from django.utils.translation import gettext as _
@functools.cache
def get_callable(lookup_view):
"""
Return a callable corresponding to lookup_view.
* If lookup_view is already a callable, return it.
* If lookup_view is a string import path that can be resolved to a
callable, import that callable and return it, otherwise raise an
exception (ImportError or ViewDoesNotExist).
"""
if callable(lookup_view):
return lookup_view
if not isinstance(lookup_view, str):
raise ViewDoesNotExist(
"'%s' is not a callable or a dot-notation path" % lookup_view
)
mod_name, func_name = get_mod_func(lookup_view)
if not func_name: # No '.' in lookup_view
raise ImportError(
"Could not import '%s'. The path must be fully qualified." % lookup_view
)
try:
mod = import_module(mod_name)
except ImportError:
parentmod, submod = get_mod_func(mod_name)
if submod and not module_has_submodule(import_module(parentmod), submod):
raise ViewDoesNotExist(
"Could not import '%s'. Parent module %s does not exist."
% (lookup_view, mod_name)
)
else:
raise
else:
try:
view_func = getattr(mod, func_name)
except AttributeError:
raise ViewDoesNotExist(
"Could not import '%s'. View does not exist in module %s."
% (lookup_view, mod_name)
)
else:
if not callable(view_func):
raise ViewDoesNotExist(
"Could not import '%s.%s'. View is not callable."
% (mod_name, func_name)
)
return view_func
def get_mod_func(callback):
# Convert 'django.views.news.stories.story_detail' to
# ['django.views.news.stories', 'story_detail']
try:
dot = callback.rindex(".")
except ValueError:
return callback, ""
return callback[:dot], callback[dot + 1 :]
# Match the beginning of a named, unnamed, or non-capturing groups.
_NAMED_GROUP_MATCHER = _lazy_re_compile(r"\(\?P(<\w+>)")
_UNNAMED_GROUP_MATCHER = _lazy_re_compile(r"\(")
_NON_CAPTURING_GROUP_MATCHER = _lazy_re_compile(r"\(\?\:")
_LITERAL_ESCAPE_RE = _lazy_re_compile(r"\\([./()_-])")
def replace_metacharacters(pattern):
"""Remove unescaped metacharacters from the pattern."""
return re.sub(
r"((?:^|(?<!\\))(?:\\\\)*)(\\?)([?*+^$]|\\[bBAZ])",
lambda m: m[1] + m[3] if m[2] else m[1],
pattern,
)
def _get_group_start_end(start, end, pattern):
# Handle nested parentheses, e.g. '^(?P<a>(x|y))/b' or '^b/((x|y)\w+)$'.
unmatched_open_brackets, prev_char = 1, None
for idx, val in enumerate(pattern[end:]):
# Check for unescaped `(` and `)`. They mark the start and end of a
# nested group.
if val == "(" and prev_char != "\\":
unmatched_open_brackets += 1
elif val == ")" and prev_char != "\\":
unmatched_open_brackets -= 1
prev_char = val
# If brackets are balanced, the end of the string for the current named
# capture group pattern has been reached.
if unmatched_open_brackets == 0:
return start, end + idx + 1
def _find_groups(pattern, group_matcher):
prev_end = None
for match in group_matcher.finditer(pattern):
if indices := _get_group_start_end(match.start(0), match.end(0), pattern):
start, end = indices
if prev_end and start > prev_end or not prev_end:
yield start, end, match
prev_end = end
def replace_named_groups(pattern):
r"""
Find named groups in `pattern` and replace them with the group name. E.g.,
1. ^(?P<a>\w+)/b/(\w+)$ ==> ^<a>/b/(\w+)$
2. ^(?P<a>\w+)/b/(?P<c>\w+)/$ ==> ^<a>/b/<c>/$
3. ^(?P<a>\w+)/b/(\w+) ==> ^<a>/b/(\w+)
4. ^(?P<a>\w+)/b/(?P<c>\w+) ==> ^<a>/b/<c>
"""
group_pattern_and_name = [
(pattern[start:end], match[1])
for start, end, match in _find_groups(pattern, _NAMED_GROUP_MATCHER)
]
for group_pattern, group_name in group_pattern_and_name:
pattern = pattern.replace(group_pattern, group_name)
return pattern
def replace_unnamed_groups(pattern):
r"""
Find unnamed groups in `pattern` and replace them with '<var>'. E.g.,
1. ^(?P<a>\w+)/b/(\w+)$ ==> ^(?P<a>\w+)/b/<var>$
2. ^(?P<a>\w+)/b/((x|y)\w+)$ ==> ^(?P<a>\w+)/b/<var>$
3. ^(?P<a>\w+)/b/(\w+) ==> ^(?P<a>\w+)/b/<var>
4. ^(?P<a>\w+)/b/((x|y)\w+) ==> ^(?P<a>\w+)/b/<var>
"""
final_pattern, prev_end = "", None
for start, end, _ignored in _find_groups(pattern, _UNNAMED_GROUP_MATCHER):
if prev_end:
final_pattern += pattern[prev_end:start]
final_pattern += pattern[:start] + "<var>"
prev_end = end
return final_pattern + pattern[prev_end:]
def remove_non_capturing_groups(pattern):
r"""
Find non-capturing groups in the given `pattern` and remove them, e.g.
1. (?P<a>\w+)/b/(?:\w+)c(?:\w+) => (?P<a>\\w+)/b/c
2. ^(?:\w+(?:\w+))a => ^a
3. ^a(?:\w+)/b(?:\w+) => ^a/b
"""
group_start_end_indices = _find_groups(pattern, _NON_CAPTURING_GROUP_MATCHER)
final_pattern, prev_end = "", None
for start, end, _ignored in group_start_end_indices:
final_pattern += pattern[prev_end:start]
prev_end = end
return final_pattern + pattern[prev_end:]
def unescape_literals(pattern):
return _LITERAL_ESCAPE_RE.sub(r"\1", pattern)
def extract_views_from_urlpatterns(urlpatterns, base="", namespace=None):
"""
Return a list of views from a list of urlpatterns.
Each object in the returned list is a 4-tuple:
(view_func, regex, namespace, name)
"""
views = []
for p in urlpatterns:
if hasattr(p, "url_patterns"):
try:
patterns = p.url_patterns
except ImportError:
continue
views.extend(
extract_views_from_urlpatterns(
patterns,
base + str(p.pattern),
(namespace or []) + (p.namespace and [p.namespace] or []),
)
)
elif hasattr(p, "callback"):
try:
views.append((p.callback, base + str(p.pattern), namespace, p.name))
except ViewDoesNotExist:
continue
else:
raise TypeError(_("%s does not appear to be a urlpattern object") % p)
return views
def simplify_regex(pattern):
r"""
Clean up urlpattern regexes into something more readable by humans. For
example, turn "^(?P<sport_slug>\w+)/athletes/(?P<athlete_slug>\w+)/$"
into "/<sport_slug>/athletes/<athlete_slug>/".
"""
pattern = remove_non_capturing_groups(pattern)
pattern = replace_named_groups(pattern)
pattern = replace_unnamed_groups(pattern)
pattern = replace_metacharacters(pattern)
pattern = unescape_literals(pattern)
if not pattern.startswith("/"):
pattern = "/" + pattern
return pattern
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