feat: introduce trigger functionality (#27644)

Signed-off-by: lyzno1 <yuanyouhuilyz@gmail.com>
Co-authored-by: Stream <Stream_2@qq.com>
Co-authored-by: lyzno1 <92089059+lyzno1@users.noreply.github.com>
Co-authored-by: zhsama <torvalds@linux.do>
Co-authored-by: Harry <xh001x@hotmail.com>
Co-authored-by: lyzno1 <yuanyouhuilyz@gmail.com>
Co-authored-by: yessenia <yessenia.contact@gmail.com>
Co-authored-by: hjlarry <hjlarry@163.com>
Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>
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Co-authored-by: WTW0313 <twwu@dify.ai>
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api/services/workflow_service.py

@@ -10,20 +10,22 @@ from sqlalchemy.orm import Session, sessionmaker
 from core.app.app_config.entities import VariableEntityType
 from core.app.apps.advanced_chat.app_config_manager import AdvancedChatAppConfigManager
 from core.app.apps.workflow.app_config_manager import WorkflowAppConfigManager
+from core.app.entities.app_invoke_entities import InvokeFrom
 from core.file import File
 from core.repositories import DifyCoreRepositoryFactory
 from core.variables import Variable
 from core.variables.variables import VariableUnion
-from core.workflow.entities import WorkflowNodeExecution
+from core.workflow.entities import GraphInitParams, GraphRuntimeState, VariablePool, WorkflowNodeExecution
 from core.workflow.enums import ErrorStrategy, WorkflowNodeExecutionMetadataKey, WorkflowNodeExecutionStatus
 from core.workflow.errors import WorkflowNodeRunFailedError
+from core.workflow.graph.graph import Graph
 from core.workflow.graph_events import GraphNodeEventBase, NodeRunFailedEvent, NodeRunSucceededEvent
 from core.workflow.node_events import NodeRunResult
 from core.workflow.nodes import NodeType
 from core.workflow.nodes.base.node import Node
+from core.workflow.nodes.node_factory import DifyNodeFactory
 from core.workflow.nodes.node_mapping import LATEST_VERSION, NODE_TYPE_CLASSES_MAPPING
 from core.workflow.nodes.start.entities import StartNodeData
-from core.workflow.runtime import VariablePool
 from core.workflow.system_variable import SystemVariable
 from core.workflow.workflow_entry import WorkflowEntry
 from events.app_event import app_draft_workflow_was_synced, app_published_workflow_was_updated
@@ -32,6 +34,7 @@ from extensions.ext_storage import storage
 from factories.file_factory import build_from_mapping, build_from_mappings
 from libs.datetime_utils import naive_utc_now
 from models import Account
+from models.enums import UserFrom
 from models.model import App, AppMode
 from models.tools import WorkflowToolProvider
 from models.workflow import Workflow, WorkflowNodeExecutionModel, WorkflowNodeExecutionTriggeredFrom, WorkflowType
@@ -211,6 +214,9 @@ class WorkflowService:
         # validate features structure
         self.validate_features_structure(app_model=app_model, features=features)
 
+        # validate graph structure
+        self.validate_graph_structure(user_id=account.id, app_model=app_model, graph=graph)
+
         # create draft workflow if not found
         if not workflow:
             workflow = Workflow(
@@ -267,6 +273,9 @@ class WorkflowService:
         if FeatureService.get_system_features().plugin_manager.enabled:
             self._validate_workflow_credentials(draft_workflow)
 
+        # validate graph structure
+        self.validate_graph_structure(user_id=account.id, app_model=app_model, graph=draft_workflow.graph_dict)
+
         # create new workflow
         workflow = Workflow.new(
             tenant_id=app_model.tenant_id,
@@ -623,7 +632,7 @@ class WorkflowService:
         node_config = draft_workflow.get_node_config_by_id(node_id)
         node_type = Workflow.get_node_type_from_node_config(node_config)
         node_data = node_config.get("data", {})
-        if node_type == NodeType.START:
+        if node_type.is_start_node:
             with Session(bind=db.engine) as session, session.begin():
                 draft_var_srv = WorkflowDraftVariableService(session)
                 conversation_id = draft_var_srv.get_or_create_conversation(
@@ -631,10 +640,11 @@ class WorkflowService:
                     app=app_model,
                     workflow=draft_workflow,
                 )
-                start_data = StartNodeData.model_validate(node_data)
-                user_inputs = _rebuild_file_for_user_inputs_in_start_node(
-                    tenant_id=draft_workflow.tenant_id, start_node_data=start_data, user_inputs=user_inputs
-                )
+                if node_type is NodeType.START:
+                    start_data = StartNodeData.model_validate(node_data)
+                    user_inputs = _rebuild_file_for_user_inputs_in_start_node(
+                        tenant_id=draft_workflow.tenant_id, start_node_data=start_data, user_inputs=user_inputs
+                    )
                 # init variable pool
                 variable_pool = _setup_variable_pool(
                     query=query,
@@ -895,6 +905,43 @@ class WorkflowService:
 
         return new_app
 
+    def validate_graph_structure(self, user_id: str, app_model: App, graph: Mapping[str, Any]):
+        """
+        Validate workflow graph structure by instantiating the Graph object.
+
+        This leverages the built-in graph validators (including trigger/UserInput exclusivity)
+        and raises any structural errors before persisting the workflow.
+        """
+        node_configs = graph.get("nodes", [])
+        node_configs = cast(list[dict[str, object]], node_configs)
+
+        # is empty graph
+        if not node_configs:
+            return
+
+        workflow_id = app_model.workflow_id or "UNKNOWN"
+        Graph.init(
+            graph_config=graph,
+            # TODO(Mairuis): Add root node id
+            root_node_id=None,
+            node_factory=DifyNodeFactory(
+                graph_init_params=GraphInitParams(
+                    tenant_id=app_model.tenant_id,
+                    app_id=app_model.id,
+                    workflow_id=workflow_id,
+                    graph_config=graph,
+                    user_id=user_id,
+                    user_from=UserFrom.ACCOUNT,
+                    invoke_from=InvokeFrom.VALIDATION,
+                    call_depth=0,
+                ),
+                graph_runtime_state=GraphRuntimeState(
+                    variable_pool=VariablePool(),
+                    start_at=time.perf_counter(),
+                ),
+            ),
+        )
+
     def validate_features_structure(self, app_model: App, features: dict):
         if app_model.mode == AppMode.ADVANCED_CHAT:
             return AdvancedChatAppConfigManager.config_validate(
@@ -997,10 +1044,11 @@ def _setup_variable_pool(
     conversation_variables: list[Variable],
 ):
     # Only inject system variables for START node type.
-    if node_type == NodeType.START:
+    if node_type == NodeType.START or node_type.is_trigger_node:
         system_variable = SystemVariable(
             user_id=user_id,
             app_id=workflow.app_id,
+            timestamp=int(naive_utc_now().timestamp()),
             workflow_id=workflow.id,
             files=files or [],
             workflow_execution_id=str(uuid.uuid4()),