Take coerce_to_string into account when handling DecimalField

Closes #62.

src/drf_yasg/inspectors/base.py

@@ -6,7 +6,7 @@ from rest_framework import serializers
 from rest_framework.utils import encoders, json
 
 from .. import openapi
-from ..utils import is_list_view
+from ..utils import decimal_as_float, is_list_view
 
 #: Sentinel value that inspectors must return to signal that they do not know how to handle an object
 NotHandled = object()
@@ -224,6 +224,8 @@ class FieldInspector(BaseInspector):
                             # JSON roundtrip ensures that the value is valid JSON;
                             # for example, sets and tuples get transformed into lists
                             default = json.loads(json.dumps(default, cls=encoders.JSONEncoder))
+                            if decimal_as_float(field):
+                                default = float(default)
                         except Exception:  # pragma: no cover
                             logger.warning("'default' on schema for %s will not be set because "
                                            "to_representation raised an exception", field, exc_info=True)

src/drf_yasg/inspectors/field.py

@@ -1,5 +1,6 @@
 import operator
 from collections import OrderedDict
+from decimal import Decimal
 
 from django.core import validators
 from django.db import models
@@ -8,7 +9,7 @@ from rest_framework.settings import api_settings as rest_framework_settings
 
 from .. import openapi
 from ..errors import SwaggerGenerationError
-from ..utils import filter_none
+from ..utils import decimal_as_float, filter_none
 from .base import FieldInspector, NotHandled, SerializerInspector
 
 
@@ -258,18 +259,29 @@ def find_limits(field):
         if isinstance(field, field_class)
     ]
 
+    if isinstance(field, serializers.DecimalField) and not decimal_as_float(field):
+        return limits
+
     for validator in field.validators:
         if not hasattr(validator, 'limit_value'):
             continue
 
+        limit_value = validator.limit_value
+        if isinstance(limit_value, Decimal) and decimal_as_float(field):
+            limit_value = float(limit_value)
+
         for validator_class, attr, improves in applicable_limits:
             if isinstance(validator, validator_class):
-                if attr not in limits or improves(validator.limit_value, limits[attr]):
-                    limits[attr] = validator.limit_value
+                if attr not in limits or improves(limit_value, limits[attr]):
+                    limits[attr] = limit_value
 
     return OrderedDict(sorted(limits.items()))
 
 
+def decimal_field_type(field):
+    return openapi.TYPE_NUMBER if decimal_as_float(field) else openapi.TYPE_STRING
+
+
 model_field_to_basic_type = [
     (models.AutoField, (openapi.TYPE_INTEGER, None)),
     (models.BinaryField, (openapi.TYPE_STRING, openapi.FORMAT_BINARY)),
@@ -277,7 +289,7 @@ model_field_to_basic_type = [
     (models.NullBooleanField, (openapi.TYPE_BOOLEAN, None)),
     (models.DateTimeField, (openapi.TYPE_STRING, openapi.FORMAT_DATETIME)),
     (models.DateField, (openapi.TYPE_STRING, openapi.FORMAT_DATE)),
-    (models.DecimalField, (openapi.TYPE_NUMBER, None)),
+    (models.DecimalField, (decimal_field_type, openapi.FORMAT_DECIMAL)),
     (models.DurationField, (openapi.TYPE_INTEGER, None)),
     (models.FloatField, (openapi.TYPE_NUMBER, None)),
     (models.IntegerField, (openapi.TYPE_INTEGER, None)),
@@ -300,9 +312,11 @@ serializer_field_to_basic_type = [
     (serializers.UUIDField, (openapi.TYPE_STRING, openapi.FORMAT_UUID)),
     (serializers.RegexField, (openapi.TYPE_STRING, None)),
     (serializers.CharField, (openapi.TYPE_STRING, None)),
-    ((serializers.BooleanField, serializers.NullBooleanField), (openapi.TYPE_BOOLEAN, None)),
+    (serializers.BooleanField, (openapi.TYPE_BOOLEAN, None)),
+    (serializers.NullBooleanField, (openapi.TYPE_BOOLEAN, None)),
     (serializers.IntegerField, (openapi.TYPE_INTEGER, None)),
-    ((serializers.FloatField, serializers.DecimalField), (openapi.TYPE_NUMBER, None)),
+    (serializers.FloatField, (openapi.TYPE_NUMBER, None)),
+    (serializers.DecimalField, (decimal_field_type, openapi.FORMAT_DECIMAL)),
     (serializers.DurationField, (openapi.TYPE_NUMBER, None)),  # ?
     (serializers.DateField, (openapi.TYPE_STRING, openapi.FORMAT_DATE)),
     (serializers.DateTimeField, (openapi.TYPE_STRING, openapi.FORMAT_DATETIME)),
@@ -326,6 +340,8 @@ def get_basic_type_info(field):
     for field_class, type_format in basic_type_info:
         if isinstance(field, field_class):
             swagger_type, format = type_format
+            if callable(swagger_type):
+                swagger_type = swagger_type(field)
             if callable(format):
                 format = format(field)
             break

src/drf_yasg/openapi.py

@@ -35,6 +35,7 @@ FORMAT_URI = "uri"  #:
 # pulled out of my ass
 FORMAT_UUID = "uuid"  #:
 FORMAT_SLUG = "slug"  #:
+FORMAT_DECIMAL = "decimal"
 
 IN_BODY = 'body'  #:
 IN_PATH = 'path'  #:

src/drf_yasg/utils.py

@@ -2,9 +2,11 @@ import inspect
 import logging
 from collections import OrderedDict
 
+from django.db import models
 from rest_framework import serializers, status
 from rest_framework.mixins import DestroyModelMixin, RetrieveModelMixin, UpdateModelMixin
 from rest_framework.request import is_form_media_type
+from rest_framework.settings import api_settings as rest_framework_settings
 from rest_framework.views import APIView
 
 logger = logging.getLogger(__name__)
@@ -273,3 +275,15 @@ def get_produces(renderer_classes):
     media_types = [renderer.media_type for renderer in renderer_classes or []]
     media_types = [encoding for encoding in media_types if 'html' not in encoding]
     return media_types
+
+
+def decimal_as_float(field):
+    """
+    Returns true if ``field`` is a django-rest-framework DecimalField and its ``coerce_to_string`` attribute or the
+    ``COERCE_DECIMAL_TO_STRING`` setting is set to ``False``.
+
+    :rtype: bool
+    """
+    if isinstance(field, serializers.DecimalField) or isinstance(field, models.DecimalField):
+        return not getattr(field, 'coerce_to_string', rest_framework_settings.COERCE_DECIMAL_TO_STRING)
+    return False