django-rest-framework/rest_framework/compat.py

"""
The `compat` module provides support for backwards compatibility with older
versions of Django/Python, and compatibility wrappers around optional packages.
"""

from __future__ import unicode_literals

import inspect

import django
from django.apps import apps
from django.conf import settings
from django.core import validators
from django.core.exceptions import ImproperlyConfigured
from django.db import models
from django.utils import six
from django.views.generic import View

try:
    from django.urls import (  # noqa
        URLPattern,
        URLResolver,
    )
except ImportError:
    # Will be removed in Django 2.0
    from django.urls import (  # noqa
        RegexURLPattern as URLPattern,
        RegexURLResolver as URLResolver,
    )


def get_regex_pattern(urlpattern):
    if hasattr(urlpattern, 'pattern'):
        # Django 2.0
        return urlpattern.pattern.regex.pattern
    else:
        # Django < 2.0
        return urlpattern.regex.pattern


def make_url_resolver(regex, urlpatterns):
    try:
        # Django 2.0
        from django.urls.resolvers import RegexPattern
        return URLResolver(RegexPattern(regex), urlpatterns)

    except ImportError:
        # Django < 2.0
        return URLResolver(regex, urlpatterns)


def unicode_repr(instance):
    # Get the repr of an instance, but ensure it is a unicode string
    # on both python 3 (already the case) and 2 (not the case).
    if six.PY2:
        return repr(instance).decode('utf-8')
    return repr(instance)


def unicode_to_repr(value):
    # Coerce a unicode string to the correct repr return type, depending on
    # the Python version. We wrap all our `__repr__` implementations with
    # this and then use unicode throughout internally.
    if six.PY2:
        return value.encode('utf-8')
    return value


def unicode_http_header(value):
    # Coerce HTTP header value to unicode.
    if isinstance(value, six.binary_type):
        return value.decode('iso-8859-1')
    return value


def distinct(queryset, base):
    if settings.DATABASES[queryset.db]["ENGINE"] == "django.db.backends.oracle":
        # distinct analogue for Oracle users
        return base.filter(pk__in=set(queryset.values_list('pk', flat=True)))
    return queryset.distinct()


def _resolve_model(obj):
    """
    Resolve supplied `obj` to a Django model class.

    `obj` must be a Django model class itself, or a string
    representation of one.  Useful in situations like GH #1225 where
    Django may not have resolved a string-based reference to a model in
    another model's foreign key definition.

    String representations should have the format:
        'appname.ModelName'
    """
    if isinstance(obj, six.string_types) and len(obj.split('.')) == 2:
        app_name, model_name = obj.split('.')
        resolved_model = apps.get_model(app_name, model_name)
        if resolved_model is None:
            msg = "Django did not return a model for {0}.{1}"
            raise ImproperlyConfigured(msg.format(app_name, model_name))
        return resolved_model
    elif inspect.isclass(obj) and issubclass(obj, models.Model):
        return obj
    raise ValueError("{0} is not a Django model".format(obj))


# django.contrib.postgres requires psycopg2
try:
    from django.contrib.postgres import fields as postgres_fields
except ImportError:
    postgres_fields = None


# coreapi is optional (Note that uritemplate is a dependency of coreapi)
try:
    import coreapi
    import uritemplate
except (ImportError, SyntaxError):
    # SyntaxError is possible under python 3.2
    coreapi = None
    uritemplate = None


# coreschema is optional
try:
    import coreschema
except ImportError:
    coreschema = None


# django-crispy-forms is optional
try:
    import crispy_forms
except ImportError:
    crispy_forms = None


# requests is optional
try:
    import requests
except ImportError:
    requests = None


# Django-guardian is optional. Import only if guardian is in INSTALLED_APPS
# Fixes (#1712). We keep the try/except for the test suite.
guardian = None
try:
    if 'guardian' in settings.INSTALLED_APPS:
        import guardian  # noqa
except ImportError:
    pass


# PATCH method is not implemented by Django
if 'patch' not in View.http_method_names:
    View.http_method_names = View.http_method_names + ['patch']


# Markdown is optional
try:
    import markdown

    if markdown.version <= '2.2':
        HEADERID_EXT_PATH = 'headerid'
        LEVEL_PARAM = 'level'
    elif markdown.version < '2.6':
        HEADERID_EXT_PATH = 'markdown.extensions.headerid'
        LEVEL_PARAM = 'level'
    else:
        HEADERID_EXT_PATH = 'markdown.extensions.toc'
        LEVEL_PARAM = 'baselevel'

    def apply_markdown(text):
        """
        Simple wrapper around :func:`markdown.markdown` to set the base level
        of '#' style headers to <h2>.
        """
        extensions = [HEADERID_EXT_PATH]
        extension_configs = {
            HEADERID_EXT_PATH: {
                LEVEL_PARAM: '2'
            }
        }
        md = markdown.Markdown(
            extensions=extensions, extension_configs=extension_configs
        )
        md_filter_add_syntax_highlight(md)
        return md.convert(text)
except ImportError:
    apply_markdown = None
    markdown = None


try:
    import pygments
    from pygments.lexers import get_lexer_by_name, TextLexer
    from pygments.formatters import HtmlFormatter

    def pygments_highlight(text, lang, style):
        lexer = get_lexer_by_name(lang, stripall=False)
        formatter = HtmlFormatter(nowrap=True, style=style)
        return pygments.highlight(text, lexer, formatter)

    def pygments_css(style):
        formatter = HtmlFormatter(style=style)
        return formatter.get_style_defs('.highlight')

except ImportError:
    pygments = None

    def pygments_highlight(text, lang, style):
        return text

    def pygments_css(style):
        return None

if markdown is not None and pygments is not None:
    # starting from this blogpost and modified to support current markdown extensions API
    # https://zerokspot.com/weblog/2008/06/18/syntax-highlighting-in-markdown-with-pygments/

    from markdown.preprocessors import Preprocessor
    import re

    class CodeBlockPreprocessor(Preprocessor):
        pattern = re.compile(
            r'^\s*``` *([^\n]+)\n(.+?)^\s*```', re.M | re.S)

        formatter = HtmlFormatter()

        def run(self, lines):
            def repl(m):
                try:
                    lexer = get_lexer_by_name(m.group(1))
                except (ValueError, NameError):
                    lexer = TextLexer()
                code = m.group(2).replace('\t', '    ')
                code = pygments.highlight(code, lexer, self.formatter)
                code = code.replace('\n\n', '\n&nbsp;\n').replace('\n', '<br />').replace('\\@', '@')
                return '\n\n%s\n\n' % code
            ret = self.pattern.sub(repl, "\n".join(lines))
            return ret.split("\n")

    def md_filter_add_syntax_highlight(md):
        md.preprocessors.add('highlight', CodeBlockPreprocessor(), "_begin")
        return True
else:
    def md_filter_add_syntax_highlight(md):
        return False

# pytz is required from Django 1.11. Remove when dropping Django 1.10 support.
try:
    import pytz  # noqa
    from pytz.exceptions import InvalidTimeError
except ImportError:
    InvalidTimeError = Exception


# `separators` argument to `json.dumps()` differs between 2.x and 3.x
# See: http://bugs.python.org/issue22767
if six.PY3:
    SHORT_SEPARATORS = (',', ':')
    LONG_SEPARATORS = (', ', ': ')
    INDENT_SEPARATORS = (',', ': ')
else:
    SHORT_SEPARATORS = (b',', b':')
    LONG_SEPARATORS = (b', ', b': ')
    INDENT_SEPARATORS = (b',', b': ')


class CustomValidatorMessage(object):
    """
    We need to avoid evaluation of `lazy` translated `message` in `django.core.validators.BaseValidator.__init__`.
    https://github.com/django/django/blob/75ed5900321d170debef4ac452b8b3cf8a1c2384/django/core/validators.py#L297

    Ref: https://github.com/encode/django-rest-framework/pull/5452
    """

    def __init__(self, *args, **kwargs):
        self.message = kwargs.pop('message', self.message)
        super(CustomValidatorMessage, self).__init__(*args, **kwargs)


class MinValueValidator(CustomValidatorMessage, validators.MinValueValidator):
    pass


class MaxValueValidator(CustomValidatorMessage, validators.MaxValueValidator):
    pass


class MinLengthValidator(CustomValidatorMessage, validators.MinLengthValidator):
    pass


class MaxLengthValidator(CustomValidatorMessage, validators.MaxLengthValidator):
    pass


def authenticate(request=None, **credentials):
    from django.contrib.auth import authenticate
    if django.VERSION < (1, 11):
        return authenticate(**credentials)
    else:
        return authenticate(request=request, **credentials)