[SILO-1087] feat: add IssueRelations external API (#8763)

* add IssueRelations external API

* update serializer methods and filter by slug

apps/api/plane/api/serializers/__init__.py

@@ -25,6 +25,10 @@ from .issue import (
     IssueCommentCreateSerializer,
     IssueLinkCreateSerializer,
     IssueLinkUpdateSerializer,
+    IssueRelationCreateSerializer,
+    IssueRelationResponseSerializer,
+    IssueRelationSerializer,
+    RelatedIssueSerializer,
 )
 from .state import StateLiteSerializer, StateSerializer
 from .cycle import (

apps/api/plane/api/serializers/issue.py

@@ -20,6 +20,7 @@ from plane.db.models import (
     IssueComment,
     IssueLabel,
     IssueLink,
+    IssueRelation,
     Label,
     ProjectMember,
     State,
@@ -479,6 +480,184 @@ class IssueLinkSerializer(BaseSerializer):
         ]
 
 
+class IssueRelationResponseSerializer(serializers.Serializer):
+    """
+    Serializer for issue relations response showing grouped relation types.
+
+    Returns issue IDs organized by relation type for efficient client-side processing.
+    """
+
+    blocking = serializers.ListField(
+        child=serializers.UUIDField(),
+        help_text="List of issue IDs that are blocking this issue",
+    )
+    blocked_by = serializers.ListField(
+        child=serializers.UUIDField(),
+        help_text="List of issue IDs that this issue is blocked by",
+    )
+    duplicate = serializers.ListField(
+        child=serializers.UUIDField(),
+        help_text="List of issue IDs that are duplicates of this issue",
+    )
+    relates_to = serializers.ListField(
+        child=serializers.UUIDField(),
+        help_text="List of issue IDs that relate to this issue",
+    )
+    start_after = serializers.ListField(
+        child=serializers.UUIDField(),
+        help_text="List of issue IDs that start after this issue",
+    )
+    start_before = serializers.ListField(
+        child=serializers.UUIDField(),
+        help_text="List of issue IDs that start before this issue",
+    )
+    finish_after = serializers.ListField(
+        child=serializers.UUIDField(),
+        help_text="List of issue IDs that finish after this issue",
+    )
+    finish_before = serializers.ListField(
+        child=serializers.UUIDField(),
+        help_text="List of issue IDs that finish before this issue",
+    )
+
+
+class IssueRelationCreateSerializer(serializers.Serializer):
+    """
+    Serializer for creating issue relations.
+
+    Creates issue relations with the specified relation type and issues.
+    Validates relation types and ensures proper issue ID format.
+    """
+
+    RELATION_TYPE_CHOICES = [
+        ("blocking", "Blocking"),
+        ("blocked_by", "Blocked By"),
+        ("duplicate", "Duplicate"),
+        ("relates_to", "Relates To"),
+        ("start_before", "Start Before"),
+        ("start_after", "Start After"),
+        ("finish_before", "Finish Before"),
+        ("finish_after", "Finish After"),
+    ]
+
+    relation_type = serializers.ChoiceField(
+        choices=RELATION_TYPE_CHOICES,
+        required=True,
+        help_text="Type of relationship between work items",
+    )
+    issues = serializers.ListField(
+        child=serializers.UUIDField(),
+        required=True,
+        min_length=1,
+        help_text="Array of work item IDs to create relations with",
+    )
+
+    def validate_issues(self, value):
+        """Validate that issues list is not empty and contains valid UUIDs."""
+        if not value:
+            raise serializers.ValidationError("At least one issue ID is required.")
+        return value
+
+
+class IssueRelationRemoveSerializer(serializers.Serializer):
+    """
+    Serializer for removing issue relations.
+
+    Removes existing relationships between work items by specifying
+    the related issue ID.
+    """
+
+    related_issue = serializers.UUIDField(
+        required=True, help_text="ID of the related work item to remove relation with"
+    )
+
+
+class IssueRelationSerializer(BaseSerializer):
+    """
+    Serializer for issue relationships showing related issue details.
+
+    Provides comprehensive information about related issues including
+    project context, sequence ID, and relationship type.
+    """
+
+    id = serializers.UUIDField(source="related_issue.id", read_only=True)
+    project_id = serializers.UUIDField(source="related_issue.project_id", read_only=True)
+    sequence_id = serializers.IntegerField(source="related_issue.sequence_id", read_only=True)
+    name = serializers.CharField(source="related_issue.name", read_only=True)
+    relation_type = serializers.CharField(read_only=True)
+    state_id = serializers.UUIDField(source="related_issue.state.id", read_only=True)
+    priority = serializers.CharField(source="related_issue.priority", read_only=True)
+
+    class Meta:
+        model = IssueRelation
+        fields = [
+            "id",
+            "project_id",
+            "sequence_id",
+            "relation_type",
+            "name",
+            "state_id",
+            "priority",
+            "created_by",
+            "created_at",
+            "updated_at",
+            "updated_by",
+        ]
+        read_only_fields = [
+            "workspace",
+            "project",
+            "created_by",
+            "created_at",
+            "updated_by",
+            "updated_at",
+        ]
+
+
+class RelatedIssueSerializer(BaseSerializer):
+    """
+    Serializer for reverse issue relationships showing issue details.
+
+    Provides comprehensive information about the source issue in a relationship
+    including project context, sequence ID, and relationship type.
+    """
+
+    id = serializers.UUIDField(source="issue.id", read_only=True)
+    project_id = serializers.PrimaryKeyRelatedField(source="issue.project_id", read_only=True)
+    sequence_id = serializers.IntegerField(source="issue.sequence_id", read_only=True)
+    name = serializers.CharField(source="issue.name", read_only=True)
+    type_id = serializers.UUIDField(source="issue.type.id", read_only=True)
+    relation_type = serializers.CharField(read_only=True)
+    is_epic = serializers.BooleanField(source="issue.type.is_epic", read_only=True)
+    state_id = serializers.UUIDField(source="issue.state.id", read_only=True)
+    priority = serializers.CharField(source="issue.priority", read_only=True)
+
+    class Meta:
+        model = IssueRelation
+        fields = [
+            "id",
+            "project_id",
+            "sequence_id",
+            "relation_type",
+            "name",
+            "type_id",
+            "is_epic",
+            "state_id",
+            "priority",
+            "created_by",
+            "created_at",
+            "updated_by",
+            "updated_at",
+        ]
+        read_only_fields = [
+            "workspace",
+            "project",
+            "created_by",
+            "created_at",
+            "updated_by",
+            "updated_at",
+        ]
+
+
 class IssueAttachmentSerializer(BaseSerializer):
     """
     Serializer for work item file attachments.

apps/api/plane/api/urls/work_item.py

@@ -17,6 +17,7 @@ from plane.api.views import (
     IssueAttachmentDetailAPIEndpoint,
     WorkspaceIssueAPIEndpoint,
     IssueSearchEndpoint,
+    IssueRelationListCreateAPIEndpoint,
 )
 
 # Deprecated url patterns
@@ -145,6 +146,11 @@ new_url_patterns = [
         IssueAttachmentDetailAPIEndpoint.as_view(http_method_names=["get", "patch", "delete"]),
         name="work-item-attachment-detail",
     ),
+    path(
+        "workspaces/<str:slug>/projects/<uuid:project_id>/work-items/<uuid:issue_id>/relations/",
+        IssueRelationListCreateAPIEndpoint.as_view(http_method_names=["get", "post"]),
+        name="work-item-relation-list",
+    ),
 ]
 
 urlpatterns = old_url_patterns + new_url_patterns

apps/api/plane/api/views/__init__.py

@@ -29,6 +29,7 @@ from .issue import (
     IssueAttachmentListCreateAPIEndpoint,
     IssueAttachmentDetailAPIEndpoint,
     IssueSearchEndpoint,
+    IssueRelationListCreateAPIEndpoint,
 )
 
 from .cycle import (

apps/api/plane/api/views/issue.py

@@ -23,7 +23,11 @@ from django.db.models import (
     Value,
     When,
     Subquery,
+    UUIDField,
 )
+from django.db.models.functions import Coalesce
+from django.contrib.postgres.aggregates import ArrayAgg
+from django.contrib.postgres.fields import ArrayField
 from django.utils import timezone
 from django.conf import settings
 
@@ -45,6 +49,9 @@ from plane.api.serializers import (
     IssueActivitySerializer,
     IssueCommentSerializer,
     IssueLinkSerializer,
+    IssueRelationCreateSerializer,
+    IssueRelationResponseSerializer,
+    IssueRelationSerializer,
     IssueSerializer,
     LabelSerializer,
     IssueAttachmentUploadSerializer,
@@ -53,6 +60,7 @@ from plane.api.serializers import (
     IssueLinkCreateSerializer,
     IssueLinkUpdateSerializer,
     LabelCreateUpdateSerializer,
+    RelatedIssueSerializer,
 )
 from plane.app.permissions import (
     ProjectEntityPermission,
@@ -66,6 +74,7 @@ from plane.db.models import (
     FileAsset,
     IssueComment,
     IssueLink,
+    IssueRelation,
     Label,
     Project,
     ProjectMember,
@@ -76,10 +85,12 @@ from plane.settings.storage import S3Storage
 from plane.bgtasks.storage_metadata_task import get_asset_object_metadata
 from .base import BaseAPIView
 from plane.utils.host import base_host
+from plane.utils.issue_relation_mapper import get_actual_relation
 from plane.bgtasks.webhook_task import model_activity
 from plane.app.permissions import ROLE
 from plane.utils.openapi import (
     work_item_docs,
+    work_item_relation_docs,
     label_docs,
     issue_link_docs,
     issue_comment_docs,
@@ -1119,9 +1130,9 @@ class IssueLinkListCreateAPIEndpoint(BaseAPIView):
         return self.paginate(
             request=request,
             queryset=(self.get_queryset()),
-            on_results=lambda issue_links: IssueLinkSerializer(
+            on_results=lambda issue_links: (
-                issue_links, many=True, fields=self.fields, expand=self.expand
+                IssueLinkSerializer(issue_links, many=True, fields=self.fields, expand=self.expand).data
-            ).data,
+            ),
         )
 
     @issue_link_docs(
@@ -1226,9 +1237,9 @@ class IssueLinkDetailAPIEndpoint(BaseAPIView):
             return self.paginate(
                 request=request,
                 queryset=(self.get_queryset()),
-                on_results=lambda issue_links: IssueLinkSerializer(
+                on_results=lambda issue_links: (
-                    issue_links, many=True, fields=self.fields, expand=self.expand
+                    IssueLinkSerializer(issue_links, many=True, fields=self.fields, expand=self.expand).data
-                ).data,
+                ),
             )
         issue_link = self.get_queryset().get(pk=pk)
         serializer = IssueLinkSerializer(issue_link, fields=self.fields, expand=self.expand)
@@ -1377,9 +1388,9 @@ class IssueCommentListCreateAPIEndpoint(BaseAPIView):
         return self.paginate(
             request=request,
             queryset=(self.get_queryset()),
-            on_results=lambda issue_comments: IssueCommentSerializer(
+            on_results=lambda issue_comments: (
-                issue_comments, many=True, fields=self.fields, expand=self.expand
+                IssueCommentSerializer(issue_comments, many=True, fields=self.fields, expand=self.expand).data
-            ).data,
+            ),
         )
 
     @issue_comment_docs(
@@ -1688,9 +1699,9 @@ class IssueActivityListAPIEndpoint(BaseAPIView):
         return self.paginate(
             request=request,
             queryset=(issue_activities),
-            on_results=lambda issue_activity: IssueActivitySerializer(
+            on_results=lambda issue_activity: (
-                issue_activity, many=True, fields=self.fields, expand=self.expand
+                IssueActivitySerializer(issue_activity, many=True, fields=self.fields, expand=self.expand).data
-            ).data,
+            ),
         )
 
 
@@ -2250,3 +2261,224 @@ class IssueSearchEndpoint(BaseAPIView):
         )[: int(limit)]
 
         return Response({"issues": issue_results}, status=status.HTTP_200_OK)
+
+
+class IssueRelationListCreateAPIEndpoint(BaseAPIView):
+    """Issue Relation List and Create Endpoint"""
+
+    serializer_class = IssueRelationSerializer
+    model = IssueRelation
+    permission_classes = [ProjectEntityPermission]
+    use_read_replica = True
+
+    @work_item_relation_docs(
+        operation_id="list_work_item_relations",
+        summary="List work item relations",
+        description="Retrieve all relationships for a work item including blocking, blocked_by, duplicate, relates_to, start_before, start_after, finish_before, and finish_after relations.",  # noqa E501
+        parameters=[
+            ISSUE_ID_PARAMETER,
+            CURSOR_PARAMETER,
+            PER_PAGE_PARAMETER,
+            ORDER_BY_PARAMETER,
+            FIELDS_PARAMETER,
+            EXPAND_PARAMETER,
+        ],
+        responses={
+            200: OpenApiResponse(
+                description="Work item relations grouped by relation type",
+                response=IssueRelationResponseSerializer,
+                examples=[
+                    OpenApiExample(
+                        name="Work Item Relations Response",
+                        value={
+                            "blocking": [
+                                "550e8400-e29b-41d4-a716-446655440000",
+                                "550e8400-e29b-41d4-a716-446655440001",
+                            ],
+                            "blocked_by": ["550e8400-e29b-41d4-a716-446655440002"],
+                            "duplicate": [],
+                            "relates_to": ["550e8400-e29b-41d4-a716-446655440003"],
+                            "start_after": [],
+                            "start_before": ["550e8400-e29b-41d4-a716-446655440004"],
+                            "finish_after": [],
+                            "finish_before": [],
+                        },
+                    )
+                ],
+            ),
+            400: INVALID_REQUEST_RESPONSE,
+            404: ISSUE_NOT_FOUND_RESPONSE,
+        },
+    )
+    def get(self, request, slug, project_id, issue_id):
+        """List work item relations
+
+        Retrieve all relationships for a work item organized by relation type.
+        Returns a structured response with relations grouped by type.
+        """
+        empty_uuid_array = Value([], output_field=ArrayField(UUIDField()))
+
+        def _agg_ids(field, **filter_kwargs):
+            return Coalesce(
+                ArrayAgg(field, filter=Q(**filter_kwargs), distinct=True),
+                empty_uuid_array,
+            )
+
+        issue_relation_qs = IssueRelation.objects.filter(
+            Q(issue_id=issue_id) | Q(related_issue_id=issue_id),
+            workspace__slug=slug,
+        )
+
+        relation_ids = issue_relation_qs.aggregate(
+            blocking_ids=_agg_ids("issue_id", relation_type="blocked_by", related_issue_id=issue_id),
+            blocked_by_ids=_agg_ids("related_issue_id", relation_type="blocked_by", issue_id=issue_id),
+            duplicate_ids=_agg_ids("related_issue_id", relation_type="duplicate", issue_id=issue_id),
+            duplicate_ids_related=_agg_ids("issue_id", relation_type="duplicate", related_issue_id=issue_id),
+            relates_to_ids=_agg_ids("related_issue_id", relation_type="relates_to", issue_id=issue_id),
+            relates_to_ids_related=_agg_ids("issue_id", relation_type="relates_to", related_issue_id=issue_id),
+            start_after_ids=_agg_ids("issue_id", relation_type="start_before", related_issue_id=issue_id),
+            start_before_ids=_agg_ids("related_issue_id", relation_type="start_before", issue_id=issue_id),
+            finish_after_ids=_agg_ids("issue_id", relation_type="finish_before", related_issue_id=issue_id),
+            finish_before_ids=_agg_ids("related_issue_id", relation_type="finish_before", issue_id=issue_id),
+        )
+
+        response_data = {
+            "blocking": relation_ids["blocking_ids"],
+            "blocked_by": relation_ids["blocked_by_ids"],
+            "duplicate": list(set(relation_ids["duplicate_ids"] + relation_ids["duplicate_ids_related"])),
+            "relates_to": list(set(relation_ids["relates_to_ids"] + relation_ids["relates_to_ids_related"])),
+            "start_after": relation_ids["start_after_ids"],
+            "start_before": relation_ids["start_before_ids"],
+            "finish_after": relation_ids["finish_after_ids"],
+            "finish_before": relation_ids["finish_before_ids"],
+        }
+
+        return Response(response_data, status=status.HTTP_200_OK)
+
+    @work_item_relation_docs(
+        operation_id="create_work_item_relation",
+        summary="Create work item relation",
+        description="Create relationships between work items. Supports various relation types including blocking, blocked_by, duplicate, relates_to, start_before, start_after, finish_before, and finish_after.",  # noqa E501
+        parameters=[
+            ISSUE_ID_PARAMETER,
+        ],
+        request=OpenApiRequest(
+            request=IssueRelationCreateSerializer,
+            examples=[
+                OpenApiExample(
+                    name="Create blocking relation",
+                    value={
+                        "relation_type": "blocking",
+                        "issues": [
+                            "550e8400-e29b-41d4-a716-446655440000",
+                            "550e8400-e29b-41d4-a716-446655440001",
+                        ],
+                    },
+                )
+            ],
+        ),
+        responses={
+            201: OpenApiResponse(
+                description="Work item relations created successfully",
+                response=IssueRelationSerializer(many=True),
+                examples=[
+                    OpenApiExample(
+                        name="Relations created",
+                        value=[
+                            {
+                                "id": "550e8400-e29b-41d4-a716-446655440000",
+                                "name": "Fix authentication bug",
+                                "sequence_id": 42,
+                                "project_id": "550e8400-e29b-41d4-a716-446655440001",
+                                "relation_type": "blocked_by",
+                                "state_id": "550e8400-e29b-41d4-a716-446655440002",
+                                "priority": "high",
+                                "created_at": "2024-01-15T10:00:00Z",
+                                "updated_at": "2024-01-15T10:00:00Z",
+                                "created_by": "550e8400-e29b-41d4-a716-446655440004",
+                                "updated_by": "550e8400-e29b-41d4-a716-446655440004",
+                            }
+                        ],
+                    )
+                ],
+            ),
+            400: INVALID_REQUEST_RESPONSE,
+            404: ISSUE_NOT_FOUND_RESPONSE,
+        },
+    )
+    def post(self, request, slug, project_id, issue_id):
+        """Create work item relation
+
+        Create relationships between work items with specified relation type.
+        Automatically tracks relation creation activity.
+        """
+        # Validate request data using serializer
+        serializer = IssueRelationCreateSerializer(data=request.data)
+        if not serializer.is_valid():
+            return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)
+
+        relation_type = serializer.validated_data["relation_type"]
+        issues = serializer.validated_data["issues"]
+        project = Project.objects.get(pk=project_id, workspace__slug=slug)
+
+        actual_relation = get_actual_relation(relation_type)
+        is_reverse = relation_type in ["blocking", "start_after", "finish_after"]
+
+        IssueRelation.objects.bulk_create(
+            [
+                IssueRelation(
+                    issue_id=(issue if is_reverse else issue_id),
+                    related_issue_id=(issue_id if is_reverse else issue),
+                    relation_type=actual_relation,
+                    project_id=project_id,
+                    workspace_id=project.workspace_id,
+                    created_by=request.user,
+                    updated_by=request.user,
+                )
+                for issue in issues
+            ],
+            batch_size=10,
+            ignore_conflicts=True,
+        )
+
+        issue_activity.delay(
+            type="issue_relation.activity.created",
+            requested_data=json.dumps(request.data, cls=DjangoJSONEncoder),
+            actor_id=str(request.user.id),
+            issue_id=str(issue_id),
+            project_id=str(project_id),
+            current_instance=None,
+            epoch=int(timezone.now().timestamp()),
+            notification=True,
+            origin=base_host(request=request, is_app=True),
+        )
+
+        # Re-fetch with select_related to avoid N+1 queries in serializers.
+        # bulk_create with ignore_conflicts=True may not return PKs,
+        # so query by the issue/related_issue pairs and relation type.
+        if is_reverse:
+            refetch_filter = Q(
+                issue_id__in=issues,
+                related_issue_id=issue_id,
+                relation_type=actual_relation,
+            )
+        else:
+            refetch_filter = Q(
+                issue_id=issue_id,
+                related_issue_id__in=issues,
+                relation_type=actual_relation,
+            )
+
+        refetched_relations = IssueRelation.objects.filter(
+            refetch_filter,
+            workspace__slug=slug,
+        ).select_related(
+            "issue__state",
+            "related_issue__state",
+        )
+
+        serializer_class = RelatedIssueSerializer if is_reverse else IssueRelationSerializer
+        return Response(
+            serializer_class(refetched_relations, many=True).data,
+            status=status.HTTP_201_CREATED,
+        )

apps/api/plane/utils/openapi/__init__.py

@@ -157,6 +157,7 @@ from .decorators import (
     user_docs,
     cycle_docs,
     work_item_docs,
+    work_item_relation_docs,
     label_docs,
     issue_link_docs,
     issue_comment_docs,
@@ -307,6 +308,7 @@ __all__ = [
     "user_docs",
     "cycle_docs",
     "work_item_docs",
+    "work_item_relation_docs",
     "label_docs",
     "issue_link_docs",
     "issue_comment_docs",

apps/api/plane/utils/openapi/decorators.py

@@ -223,6 +223,21 @@ def issue_attachment_docs(**kwargs):
     return extend_schema(**_merge_schema_options(defaults, kwargs))
 
 
+def work_item_relation_docs(**kwargs):
+    """Decorator for work item relation endpoints"""
+    defaults = {
+        "tags": ["Work Item Relations"],
+        "parameters": [WORKSPACE_SLUG_PARAMETER, PROJECT_ID_PARAMETER],
+        "responses": {
+            401: UNAUTHORIZED_RESPONSE,
+            403: FORBIDDEN_RESPONSE,
+            404: NOT_FOUND_RESPONSE,
+        },
+    }
+
+    return extend_schema(**_merge_schema_options(defaults, kwargs))
+
+
 def module_docs(**kwargs):
     """Decorator for module management endpoints"""
     defaults = {