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.
"""

# flake8: noqa
from __future__ import unicode_literals

import django
from django.conf import settings
from django.db import connection, transaction
from django.utils import six
from django.views.generic import View

try:
    import importlib  # Available in Python 3.1+
except ImportError:
    from django.utils import importlib  # Will be removed in Django 1.9


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 total_seconds(timedelta):
    # TimeDelta.total_seconds() is only available in Python 2.7
    if hasattr(timedelta, 'total_seconds'):
        return timedelta.total_seconds()
    else:
        return (timedelta.days * 86400.0) + float(timedelta.seconds) + (timedelta.microseconds / 1000000.0)


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()


# contrib.postgres only supported from 1.8 onwards.
try:
    from django.contrib.postgres import fields as postgres_fields
except ImportError:
    postgres_fields = None


# django-filter is optional
try:
    import django_filters
except ImportError:
    django_filters = 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:
    import guardian
    import guardian.shortcuts  # Fixes #1624
except ImportError:
    pass


# MinValueValidator, MaxValueValidator et al. only accept `message` in 1.8+
if django.VERSION >= (1, 8):
    from django.core.validators import MinValueValidator, MaxValueValidator
    from django.core.validators import MinLengthValidator, MaxLengthValidator
else:
    from django.core.validators import MinValueValidator as DjangoMinValueValidator
    from django.core.validators import MaxValueValidator as DjangoMaxValueValidator
    from django.core.validators import MinLengthValidator as DjangoMinLengthValidator
    from django.core.validators import MaxLengthValidator as DjangoMaxLengthValidator


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


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


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


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


# 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


    def apply_markdown(text):
        """
        Simple wrapper around :func:`markdown.markdown` to set the base level
        of '#' style headers to <h2>.
        """

        extensions = ['headerid(level=2)']
        safe_mode = False
        md = markdown.Markdown(extensions=extensions, safe_mode=safe_mode)
        return md.convert(text)
except ImportError:
    apply_markdown = None


# `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': ')

if django.VERSION >= (1, 8):
    from django.db.models import DurationField
    from django.utils.dateparse import parse_duration
    from django.utils.duration import duration_string
else:
    DurationField = duration_string = parse_duration = None


def set_rollback():
    if hasattr(transaction, 'set_rollback'):
        if connection.settings_dict.get('ATOMIC_REQUESTS', False):
            # If running in >=1.6 then mark a rollback as required,
            # and allow it to be handled by Django.
            if connection.in_atomic_block:
                transaction.set_rollback(True)
    elif transaction.is_managed():
        # Otherwise handle it explicitly if in managed mode.
        if transaction.is_dirty():
            transaction.rollback()
        transaction.leave_transaction_management()
    else:
        # transaction not managed
        pass