Allowed fields to specify their own metadata.

rest_framework/fields.py

@@ -24,7 +24,7 @@ from django.utils.dateparse import (
     parse_date, parse_datetime, parse_duration, parse_time
 )
 from django.utils.duration import duration_string
-from django.utils.encoding import is_protected_type, smart_text
+from django.utils.encoding import force_text, is_protected_type, smart_text
 from django.utils.functional import cached_property
 from django.utils.ipv6 import clean_ipv6_address
 from django.utils.translation import ugettext_lazy as _
@@ -262,6 +262,7 @@ MISSING_ERROR_MESSAGE = (
 class Field(object):
     _creation_counter = 0
 
+    type = 'field'
     default_error_messages = {
         'required': _('This field is required.'),
         'null': _('This field may not be null.')
@@ -597,10 +598,23 @@ class Field(object):
         """
         return unicode_to_repr(representation.field_repr(self))
 
+    def get_metadata(self):
+        metadata = OrderedDict([
+            ('type', self.type),
+            ('required', self.required),
+            ('read_only', self.read_only),
+        ])
+        for attr in ['label', 'help_text']:
+            value = getattr(self, attr)
+            if value is not None and value != '':
+                metadata[attr] = force_text(value, strings_only=True)
+        return metadata
+
 
 # Boolean types...
 
 class BooleanField(Field):
+    type = 'boolean'
     default_error_messages = {
         'invalid': _('"{input}" is not a valid boolean.')
     }
@@ -632,6 +646,7 @@ class BooleanField(Field):
 
 
 class NullBooleanField(Field):
+    type = 'boolean'
     default_error_messages = {
         'invalid': _('"{input}" is not a valid boolean.')
     }
@@ -667,6 +682,7 @@ class NullBooleanField(Field):
 # String types...
 
 class CharField(Field):
+    type = 'string'
     default_error_messages = {
         'blank': _('This field may not be blank.'),
         'max_length': _('Ensure this field has no more than {max_length} characters.'),
@@ -704,8 +720,17 @@ class CharField(Field):
     def to_representation(self, value):
         return six.text_type(value)
 
+    def get_metadata(self):
+        metadata = super(CharField, self).get_metadata()
+        for attr in ['min_length', 'max_length']:
+            value = getattr(self, attr)
+            if value is not None:
+                metadata[attr] = value
+        return metadata
+
 
 class EmailField(CharField):
+    type = 'email'
     default_error_messages = {
         'invalid': _('Enter a valid email address.')
     }
@@ -717,6 +742,7 @@ class EmailField(CharField):
 
 
 class RegexField(CharField):
+    type = 'regex'
     default_error_messages = {
         'invalid': _('This value does not match the required pattern.')
     }
@@ -728,6 +754,7 @@ class RegexField(CharField):
 
 
 class SlugField(CharField):
+    type = 'slug'
     default_error_messages = {
         'invalid': _('Enter a valid "slug" consisting of letters, numbers, underscores or hyphens.')
     }
@@ -740,6 +767,7 @@ class SlugField(CharField):
 
 
 class URLField(CharField):
+    type = 'url'
     default_error_messages = {
         'invalid': _('Enter a valid URL.')
     }
@@ -814,6 +842,7 @@ class IPAddressField(CharField):
 # Number types...
 
 class IntegerField(Field):
+    type = 'integer'
     default_error_messages = {
         'invalid': _('A valid integer is required.'),
         'max_value': _('Ensure this value is less than or equal to {max_value}.'),
@@ -847,8 +876,17 @@ class IntegerField(Field):
     def to_representation(self, value):
         return int(value)
 
+    def get_metadata(self):
+        metadata = super(IntegerField, self).get_metadata()
+        for attr in ['max_value', 'min_value']:
+            value = getattr(self, attr)
+            if value is not None:
+                metadata[attr] = value
+        return metadata
+
 
 class FloatField(Field):
+    type = 'float'
     default_error_messages = {
         'invalid': _('A valid number is required.'),
         'max_value': _('Ensure this value is less than or equal to {max_value}.'),
@@ -880,8 +918,17 @@ class FloatField(Field):
     def to_representation(self, value):
         return float(value)
 
+    def get_metadata(self):
+        metadata = super(FloatField, self).get_metadata()
+        for attr in ['max_value', 'min_value']:
+            value = getattr(self, attr)
+            if value is not None:
+                metadata[attr] = value
+        return metadata
+
 
 class DecimalField(Field):
+    type = 'decimal'
     default_error_messages = {
         'invalid': _('A valid number is required.'),
         'max_value': _('Ensure this value is less than or equal to {max_value}.'),
@@ -998,10 +1045,19 @@ class DecimalField(Field):
             decimal.Decimal('.1') ** self.decimal_places,
             context=context)
 
+    def get_metadata(self):
+        metadata = super(DecimalField, self).get_metadata()
+        for attr in ['max_value', 'min_value']:
+            value = getattr(self, attr)
+            if value is not None:
+                metadata[attr] = value
+        return metadata
+
 
 # Date & time fields...
 
 class DateTimeField(Field):
+    type = 'datetime'
     default_error_messages = {
         'invalid': _('Datetime has wrong format. Use one of these formats instead: {format}.'),
         'date': _('Expected a datetime but got a date.'),
@@ -1080,6 +1136,7 @@ class DateTimeField(Field):
 
 
 class DateField(Field):
+    type = 'date'
     default_error_messages = {
         'invalid': _('Date has wrong format. Use one of these formats instead: {format}.'),
         'datetime': _('Expected a date but got a datetime.'),
@@ -1149,6 +1206,7 @@ class DateField(Field):
 
 
 class TimeField(Field):
+    type = 'time'
     default_error_messages = {
         'invalid': _('Time has wrong format. Use one of these formats instead: {format}.'),
     }
@@ -1232,6 +1290,7 @@ class DurationField(Field):
 # Choice types...
 
 class ChoiceField(Field):
+    type = 'choice'
     default_error_messages = {
         'invalid_choice': _('"{input}" is not a valid choice.')
     }
@@ -1279,8 +1338,21 @@ class ChoiceField(Field):
             cutoff_text=self.html_cutoff_text
         )
 
+    def get_metadata(self):
+        metadata = super(ChoiceField, self).get_metadata()
+        if not self.read_only:
+            metadata['choices'] = [
+                {
+                    'value': choice_value,
+                    'display_name': force_text(choice_name, strings_only=True)
+                }
+                for choice_value, choice_name in self.choices.items()
+            ]
+        return metadata
+
 
 class MultipleChoiceField(ChoiceField):
+    type = 'multiple choice'
     default_error_messages = {
         'invalid_choice': _('"{input}" is not a valid choice.'),
         'not_a_list': _('Expected a list of items but got type "{input_type}".'),
@@ -1339,6 +1411,7 @@ class FilePathField(ChoiceField):
 # File types...
 
 class FileField(Field):
+    type = 'file upload'
     default_error_messages = {
         'required': _('No file was submitted.'),
         'invalid': _('The submitted data was not a file. Check the encoding type on the form.'),
@@ -1388,8 +1461,15 @@ class FileField(Field):
             return url
         return value.name
 
+    def get_metadata(self):
+        metadata = super(FileField, self).get_metadata()
+        if self.max_length is not None:
+            metadata['max_length'] = self.max_length
+        return metadata
+
 
 class ImageField(FileField):
+    type = 'image upload'
     default_error_messages = {
         'invalid_image': _(
             'Upload a valid image. The file you uploaded was either not an image or a corrupted image.'
@@ -1427,6 +1507,7 @@ class _UnvalidatedField(Field):
 
 
 class ListField(Field):
+    type = 'list'
     child = _UnvalidatedField()
     initial = []
     default_error_messages = {
@@ -1479,8 +1560,14 @@ class ListField(Field):
         """
         return [self.child.to_representation(item) for item in data]
 
+    def get_metadata(self):
+        metadata = super(ListField, self).get_metadata()
+        metadata['child'] = self.child.get_metadata()
+        return metadata
+
 
 class DictField(Field):
+    type = 'nested object'
     child = _UnvalidatedField()
     initial = {}
     default_error_messages = {
@@ -1528,6 +1615,11 @@ class DictField(Field):
             for key, val in value.items()
         }
 
+    def get_metadata(self):
+        metadata = super(DictField, self).get_metadata()
+        metadata['child'] = self.child.get_metadata()
+        return metadata
+
 
 class JSONField(Field):
     default_error_messages = {

rest_framework/metadata.py

@@ -103,47 +103,11 @@ class SimpleMetadata(BaseMetadata):
         Given an instance of a serializer, return a dictionary of metadata
         about its fields.
         """
-        if hasattr(serializer, 'child'):
+        return serializer.get_metadata()
-            # If this is a `ListSerializer` then we want to examine the
-            # underlying child serializer instance instead.
-            serializer = serializer.child
-        return OrderedDict([
-            (field_name, self.get_field_info(field))
-            for field_name, field in serializer.fields.items()
-        ])
 
     def get_field_info(self, field):
         """
         Given an instance of a serializer field, return a dictionary
         of metadata about it.
         """
-        field_info = OrderedDict()
+        return field.get_metadata()
-        field_info['type'] = self.label_lookup[field]
-        field_info['required'] = getattr(field, 'required', False)
-
-        attrs = [
-            'read_only', 'label', 'help_text',
-            'min_length', 'max_length',
-            'min_value', 'max_value'
-        ]
-
-        for attr in attrs:
-            value = getattr(field, attr, None)
-            if value is not None and value != '':
-                field_info[attr] = force_text(value, strings_only=True)
-
-        if getattr(field, 'child', None):
-            field_info['child'] = self.get_field_info(field.child)
-        elif getattr(field, 'fields', None):
-            field_info['children'] = self.get_serializer_info(field)
-
-        if not field_info.get('read_only') and hasattr(field, 'choices'):
-            field_info['choices'] = [
-                {
-                    'value': choice_value,
-                    'display_name': force_text(choice_name, strings_only=True)
-                }
-                for choice_value, choice_name in field.choices.items()
-            ]
-
-        return field_info

rest_framework/relations.py

@@ -10,7 +10,7 @@ from django.core.urlresolvers import (
 from django.db.models import Manager
 from django.db.models.query import QuerySet
 from django.utils import six
-from django.utils.encoding import smart_text
+from django.utils.encoding import force_text, smart_text
 from django.utils.six.moves.urllib import parse as urlparse
 from django.utils.translation import ugettext_lazy as _
 
@@ -186,6 +186,18 @@ class RelatedField(Field):
     def display_value(self, instance):
         return six.text_type(instance)
 
+    def get_metadata(self):
+        metadata = super(RelatedField, self).get_metadata()
+        if not self.read_only:
+            metadata['choices'] = [
+                {
+                    'value': choice_value,
+                    'display_name': force_text(choice_name, strings_only=True)
+                }
+                for choice_value, choice_name in self.choices.items()
+            ]
+        return metadata
+
 
 class StringRelatedField(RelatedField):
     """

rest_framework/serializers.py

@@ -322,6 +322,7 @@ def get_validation_error_detail(exc):
 
 @six.add_metaclass(SerializerMetaclass)
 class Serializer(BaseSerializer):
+    type = 'nested object'
     default_error_messages = {
         'invalid': _('Invalid data. Expected a dictionary, but got {datatype}.')
     }
@@ -512,6 +513,17 @@ class Serializer(BaseSerializer):
         ret = super(Serializer, self).errors
         return ReturnDict(ret, serializer=self)
 
+    def get_metadata(self):
+        fields_metadata = OrderedDict([
+            (field_name, field.get_metadata())
+            for field_name, field in self.fields.items()
+        ])
+        if self.root is self:
+            return fields_metadata
+        metadata = super(Serializer, self).get_metadata()
+        metadata['children'] = fields_metadata
+        return metadata
+
 
 # There's some replication of `ListField` here,
 # but that's probably better than obfuscating the call hierarchy.
@@ -685,6 +697,16 @@ class ListSerializer(BaseSerializer):
             return ReturnDict(ret, serializer=self)
         return ReturnList(ret, serializer=self)
 
+    def get_metadata(self):
+        if self.root is self:
+            return OrderedDict([
+                (field_name, field.get_metadata())
+                for field_name, field in self.child.fields.items()
+            ])
+        metadata = super(ListSerializer, self).get_metadata()
+        metadata['child'] = self.child.get_metadata()
+        return metadata
+
 
 # ModelSerializer & HyperlinkedModelSerializer
 # --------------------------------------------