Split Distribution into two objects

The Distribution contained options which should not be mixed.
Specifically the repository and repository_version options go together
and the publication goes by itself.

This PR splits that object into two new objects
RepositoryVersionDistribution and PublicationDistribution. Each receives
a viewset, serializer, and filterset to match. Each also is a full
Detail model and can be used by plugins without additional code from
them.

https://pulp.plan.io/issues/4785
closes #4785

pulpcore/app/migrations/0001_initial.py

@@ -1,4 +1,4 @@
-# Generated by Django 2.2.1 on 2019-05-08 18:30
+# Generated by Django 2.2.1 on 2019-05-08 21:46
 
 from django.conf import settings
 import django.core.validators
@@ -376,6 +376,18 @@ class Migration(migrations.Migration):
             },
             bases=('core.progressreport',),
         ),
+        migrations.CreateModel(
+            name='RepositoryVersionDistribution',
+            fields=[
+                ('basedistribution_ptr', models.OneToOneField(auto_created=True, on_delete=django.db.models.deletion.CASCADE, parent_link=True, primary_key=True, related_name='_repository_version_distributions', serialize=False, to='core.BaseDistribution')),
+                ('repository', models.ForeignKey(null=True, on_delete=django.db.models.deletion.SET_NULL, related_name='_repository_version_distributions', to='core.Repository')),
+                ('repository_version', models.ForeignKey(null=True, on_delete=django.db.models.deletion.SET_NULL, related_name='_repository_version_distributions', to='core.RepositoryVersion')),
+            ],
+            options={
+                'default_related_name': '_repository_version_distributions',
+            },
+            bases=('core.basedistribution',),
+        ),
         migrations.CreateModel(
             name='RemoteArtifact',
             fields=[
@@ -425,19 +437,17 @@ class Migration(migrations.Migration):
             ],
             options={
                 'default_related_name': 'published_artifact',
-                'unique_together': {('publication', 'content_artifact'), ('publication', 'relative_path')},
+                'unique_together': {('publication', 'relative_path'), ('publication', 'content_artifact')},
             },
         ),
         migrations.CreateModel(
-            name='Distribution',
+            name='PublicationDistribution',
             fields=[
-                ('basedistribution_ptr', models.OneToOneField(auto_created=True, on_delete=django.db.models.deletion.CASCADE, parent_link=True, primary_key=True, related_name='_distributions', serialize=False, to='core.BaseDistribution')),
-                ('publication', models.ForeignKey(null=True, on_delete=django.db.models.deletion.SET_NULL, related_name='_distributions', to='core.Publication')),
-                ('repository', models.ForeignKey(null=True, on_delete=django.db.models.deletion.SET_NULL, related_name='_distributions', to='core.Repository')),
-                ('repository_version', models.ForeignKey(null=True, on_delete=django.db.models.deletion.SET_NULL, related_name='_distributions', to='core.RepositoryVersion')),
+                ('basedistribution_ptr', models.OneToOneField(auto_created=True, on_delete=django.db.models.deletion.CASCADE, parent_link=True, primary_key=True, related_name='_publication_distributions', serialize=False, to='core.BaseDistribution')),
+                ('publication', models.ForeignKey(null=True, on_delete=django.db.models.deletion.SET_NULL, related_name='_publication_distributions', to='core.Publication')),
             ],
             options={
-                'default_related_name': '_distributions',
+                'default_related_name': '_publication_distributions',
             },
             bases=('core.basedistribution',),
         ),

pulpcore/app/models/__init__.py

@@ -6,10 +6,11 @@
 from .publication import (  # noqa
     ContentGuard,
     BaseDistribution,
-    Distribution,
     Publication,
+    PublicationDistribution,
     PublishedArtifact,
-    PublishedMetadata
+    PublishedMetadata,
+    RepositoryVersionDistribution,
 )
 from .repository import (  # noqa
     Exporter,

pulpcore/app/models/publication.py

@@ -232,23 +232,38 @@ class BaseDistribution(MasterModel):
     remote = models.ForeignKey(Remote, null=True, on_delete=models.SET_NULL)
 
 
-class Distribution(BaseDistribution):
+class PublicationDistribution(BaseDistribution):
     """
-    A distribution defines how a publication is distributed by Pulp's content app.
-
-    The use of repository, repository_version, or publication are mutually exclusive, and this
-    model's serializer will raise a ValidationError if they are used together.
+    Define how Pulp's content app will serve a :term:`Publication`.
 
     Relations:
         publication (models.ForeignKey): Publication to be served.
+    """
+
+    TYPE = 'publication_distributions'
+
+    publication = models.ForeignKey(Publication, null=True, on_delete=models.SET_NULL)
+
+    class Meta:
+        default_related_name = '_publication_distributions'
+
+
+class RepositoryVersionDistribution(BaseDistribution):
+    """
+    Define how Pulp's content app will serve a :term:`RepositoryVersion` or :term:`Repository`.
+
+    The ``repository`` and ``repository_version`` fields cannot be used together.
+
+    Relations:
         repository (models.ForeignKey): The latest RepositoryVersion for this Repository will be
             served.
         repository_version (models.ForeignKey): RepositoryVersion to be served.
     """
 
-    publication = models.ForeignKey(Publication, null=True, on_delete=models.SET_NULL)
+    TYPE = 'repository_version_distributions'
+
     repository = models.ForeignKey(Repository, null=True, on_delete=models.SET_NULL)
     repository_version = models.ForeignKey(RepositoryVersion, null=True, on_delete=models.SET_NULL)
 
     class Meta:
-        default_related_name = '_distributions'
+        default_related_name = '_repository_version_distributions'

pulpcore/app/serializers/__init__.py

@@ -35,8 +35,9 @@
 from .publication import (  # noqa
     BaseDistributionSerializer,
     ContentGuardSerializer,
-    DistributionSerializer,
     PublicationSerializer,
+    PublicationDistributionSerializer,
+    RepositoryVersionDistributionSerializer,
 )
 from .repository import (  # noqa
     ExporterSerializer,

pulpcore/app/serializers/publication.py

@@ -21,7 +21,7 @@
 
 class PublicationSerializer(MasterModelSerializer):
     _href = DetailIdentityField()
-    _distributions = DetailRelatedField(
+    _publication_distributions = DetailRelatedField(
        help_text=_('This publication is currently being served as'
                    'defined by these distributions.'),
        many=True,
@@ -71,8 +71,8 @@ class Meta:
         abstract = True
         model = models.Publication
         fields = MasterModelSerializer.Meta.fields + (
+            '_publication_distributions',
             'publisher',
-            '_distributions',
             'repository_version',
             'repository'
         )
@@ -100,20 +100,35 @@ class Meta:
 
 class BaseDistributionSerializer(MasterModelSerializer):
     _href = DetailIdentityField()
+    base_path = serializers.CharField(
+        help_text=_('The base (relative) path component of the published url. Avoid paths that \
+                    overlap with other distribution base paths (e.g. "foo" and "foo/bar")'),
+        validators=[validators.MaxLengthValidator(
+            models.BaseDistribution._meta.get_field('base_path').max_length,
+            message=_('`base_path` length must be less than {} characters').format(
+                models.BaseDistribution._meta.get_field('base_path').max_length
+            )),
+            UniqueValidator(queryset=models.BaseDistribution.objects.all()),
+        ]
+    )
+    base_url = BaseURLField(
+        source='base_path', read_only=True,
+        help_text=_('The URL for accessing the publication as defined by this distribution.')
+    )
     content_guard = DetailRelatedField(
         required=False,
         help_text=_('An optional content-guard.'),
         queryset=models.ContentGuard.objects.all(),
         allow_null=True
     )
     name = serializers.CharField(
-        help_text=_('A unique distribution name. Ex, `rawhide` and `stable`.'),
+        help_text=_('A unique name. Ex, `rawhide` and `stable`.'),
         validators=[validators.MaxLengthValidator(
-            models.Distribution._meta.get_field('name').max_length,
-            message=_('Distribution name length must be less than {} characters').format(
-                models.Distribution._meta.get_field('name').max_length
+            models.BaseDistribution._meta.get_field('name').max_length,
+            message=_('`name` length must be less than {} characters').format(
+                models.BaseDistribution._meta.get_field('name').max_length
             )),
-            UniqueValidator(queryset=models.Distribution.objects.all())]
+            UniqueValidator(queryset=models.BaseDistribution.objects.all())]
     )
     remote = DetailRelatedField(
         required=False,
@@ -124,61 +139,13 @@ class BaseDistributionSerializer(MasterModelSerializer):
 
     class Meta:
         fields = ModelSerializer.Meta.fields + (
+            'base_path',
+            'base_url',
             'content_guard',
             'name',
             'remote',
         )
 
-
-class DistributionSerializer(BaseDistributionSerializer):
-    base_path = serializers.CharField(
-        help_text=_('The base (relative) path component of the published url. Avoid paths that \
-                    overlap with other distribution base paths (e.g. "foo" and "foo/bar")'),
-        validators=[validators.MaxLengthValidator(
-            models.Distribution._meta.get_field('base_path').max_length,
-            message=_('Distribution base_path length must be less than {} characters').format(
-                models.Distribution._meta.get_field('base_path').max_length
-            )),
-            UniqueValidator(queryset=models.Distribution.objects.all()),
-        ]
-    )
-    base_url = BaseURLField(
-        source='base_path', read_only=True,
-        help_text=_('The URL for accessing the publication as defined by this distribution.')
-    )
-    publication = DetailRelatedField(
-        required=False,
-        help_text=_('Publication to be served'),
-        queryset=models.Publication.objects.exclude(complete=False),
-        allow_null=True
-    )
-    repository = RelatedField(
-        required=False,
-        help_text=_('The latest RepositoryVersion for this Repository will be served.'),
-        queryset=models.Repository.objects.all(),
-        view_name='repositories-detail',
-        allow_null=True
-    )
-    repository_version = NestedRelatedField(
-        required=False,
-        help_text=_('RepositoryVersion to be served'),
-        queryset=models.RepositoryVersion.objects.exclude(complete=False),
-        view_name='versions-detail',
-        allow_null=True,
-        lookup_field='number',
-        parent_lookup_kwargs={'repository_pk': 'repository__pk'},
-    )
-
-    class Meta:
-        model = models.Distribution
-        fields = BaseDistributionSerializer.Meta.fields + (
-            'base_path',
-            'base_url',
-            'publication',
-            'repository',
-            'repository_version',
-        )
-
     def _validate_path_overlap(self, path):
         # look for any base paths nested in path
         search = path.split("/")[0]
@@ -208,14 +175,50 @@ def validate_base_path(self, path):
     def validate(self, data):
         super().validate(data)
 
-        mutex_keys = ['publication', 'repository', 'repository_version']
-        in_use_keys = []
-        for mkey in mutex_keys:
-            if mkey in data:
-                in_use_keys.append(mkey)
-
-        if len(in_use_keys) > 1:
-            msg = _("The attributes {keys} must be used exclusively.".format(keys=in_use_keys))
+        if 'repository' in data and 'repository_version' in data:
+            msg = _("The attributes 'repository' and 'repository_version' must be used"
+                    "exclusively.")
             raise serializers.ValidationError(msg)
 
         return data
+
+
+class PublicationDistributionSerializer(BaseDistributionSerializer):
+    publication = DetailRelatedField(
+        required=False,
+        help_text=_('Publication to be served'),
+        queryset=models.Publication.objects.exclude(complete=False),
+        allow_null=True
+    )
+
+    class Meta:
+        model = models.PublicationDistribution
+        fields = BaseDistributionSerializer.Meta.fields + (
+            'publication',
+        )
+
+
+class RepositoryVersionDistributionSerializer(BaseDistributionSerializer):
+    repository = RelatedField(
+        required=False,
+        help_text=_('The latest RepositoryVersion for this Repository will be served.'),
+        queryset=models.Repository.objects.all(),
+        view_name='repositories-detail',
+        allow_null=True
+    )
+    repository_version = NestedRelatedField(
+        required=False,
+        help_text=_('RepositoryVersion to be served'),
+        queryset=models.RepositoryVersion.objects.exclude(complete=False),
+        view_name='versions-detail',
+        allow_null=True,
+        lookup_field='number',
+        parent_lookup_kwargs={'repository_pk': 'repository__pk'},
+    )
+
+    class Meta:
+        model = models.RepositoryVersionDistribution
+        fields = BaseDistributionSerializer.Meta.fields + (
+            'repository',
+            'repository_version',
+        )

pulpcore/app/viewsets/__init__.py

@@ -18,8 +18,9 @@
 from .publication import (  # noqa
     ContentGuardFilter,
     ContentGuardViewSet,
-    DistributionViewSet,
+    PublicationDistributionViewSet,
     PublicationViewSet,
+    RepositoryVersionDistributionViewSet,
 )
 from .repository import (  # noqa
     ExporterViewSet,