Merge pull request #150 from daviddavis/issue4827

Adding checksum serializer for content

pulpcore/app/serializers/__init__.py

@@ -23,6 +23,7 @@
 )
 from .content import (  # noqa
     ArtifactSerializer,
+    ContentChecksumSerializer,
     NoArtifactContentSerializer,
     SingleArtifactContentSerializer,
     MultipleArtifactContentSerializer,

pulpcore/app/serializers/content.py

@@ -91,6 +91,51 @@ class Meta:
         fields = BaseContentSerializer.Meta.fields + ('_artifacts',)
 
 
+class ContentChecksumSerializer(serializers.Serializer):
+    """
+    Provide a serializer with artifact checksum fields for single artifact content.
+
+    If you use this serializer, it's recommended that you prefetch artifacts:
+
+        Content.objects.prefetch_related("_artifacts").all()
+    """
+
+    md5 = fields.ContentArtifactChecksumField(
+        help_text=_("The MD5 checksum if available."),
+        checksum='md5',
+    )
+
+    sha1 = fields.ContentArtifactChecksumField(
+        help_text=_("The SHA-1 checksum if available."),
+        checksum='sha1',
+    )
+
+    sha224 = fields.ContentArtifactChecksumField(
+        help_text=_("The SHA-224 checksum if available."),
+        checksum='sha224',
+    )
+
+    sha256 = fields.ContentArtifactChecksumField(
+        help_text=_("The SHA-256 checksum if available."),
+        checksum='sha256',
+    )
+
+    sha384 = fields.ContentArtifactChecksumField(
+        help_text=_("The SHA-384 checksum if available."),
+        checksum='sha384',
+    )
+
+    sha512 = fields.ContentArtifactChecksumField(
+        help_text=_("The SHA-512 checksum if available."),
+        checksum='sha512',
+    )
+
+    class Meta:
+        model = models.Artifact
+        fields = base.ModelSerializer.Meta.fields + ('md5', 'sha1', 'sha224', 'sha256', 'sha384',
+                                                     'sha512')
+
+
 class ArtifactSerializer(base.ModelSerializer):
     _href = base.IdentityField(
         view_name='artifacts-detail',

pulpcore/app/serializers/fields.py

@@ -49,15 +49,54 @@ def get_attribute(self, instance):
         Returns:
             A single Artifact model related to the instance of Content.
         """
-        try:
-            return instance._artifacts.get()
-        except models.Artifact.DoesNotExist:
+        # using get() and first() will query the db. count() and all() will use cached artifacts if
+        # they are prefetched.
+        if instance._artifacts.count() == 0:
             return None
-        except models.Artifact.MultipleObjectsReturned:
+        if instance._artifacts.count() == 1:
+            return instance._artifacts.all()[0]
+        if instance._artifacts.count() > 1:
             raise ValueError(_("SingleContentArtifactField should not be used in a context where "
                                "multiple artifacts for one content is possible."))
 
 
+class ContentArtifactChecksumField(serializers.CharField):
+    """
+    A serializer field for the artifact checksum Content model (single-artifact).
+    """
+
+    def __init__(self, *args, **kwargs):
+        kwargs['read_only'] = True
+        self.checksum = kwargs.pop('checksum', 'md5')
+        super().__init__(*args, **kwargs)
+
+    def get_attribute(self, instance):
+        """
+        Returns the field from the instance that should be serialized using this serializer field.
+
+        This serializer looks up the checksum for single artifact content
+
+        Args:
+            instance (:class:`pulpcore.app.models.Content`): An instance of Content being
+                serialized.
+
+        Returns:
+            A string of the checksum or None.
+
+        Raises:
+            :class:`rest_framework.exceptions.ValidationError`: When more than one Artifacts exist.
+        """
+        # using get() and first() will query the db. count() and all() will use cached artifacts if
+        # they are prefetched.
+        if instance._artifacts.count() == 0:
+            return None
+        if instance._artifacts.count() == 1:
+            return getattr(instance._artifacts.all()[0], self.checksum)
+        if instance._artifacts.count() > 1:
+            raise ValueError(_("ContentArtifactChecksumField should not be used in a context where "
+                               "multiple artifacts for one content is possible."))
+
+
 class ContentArtifactsField(serializers.DictField):
     """
     A serializer field for the '_artifacts' ManyToManyField on the Content model.