feat(vue-flow): add autoConnect option

# What's changed?

* auto-connect allows to easily enable the default add edge change handler (shown in the examples)
* allow auto-connect to be a function that returns false when connection is cancelled or partial edge when it should be created

Author: bcakmakoglu

packages/vue-flow/src/container/VueFlow/VueFlow.vue

@@ -36,6 +36,7 @@ const props = withDefaults(defineProps<FlowProps>(), {
   fitViewOnInit: undefined,
   connectOnClick: undefined,
   connectionLineStyle: undefined,
+  autoConnect: undefined,
 })
 
 const emit = defineEmits<{

packages/vue-flow/src/container/VueFlow/watch.ts

@@ -1,6 +1,7 @@
 import type { Ref, ToRefs } from 'vue'
 import type { WatchPausableReturn } from '@vueuse/core'
-import type { FlowProps, GraphEdge, GraphNode, VueFlowStore } from '~/types'
+import { isFunction } from '@vueuse/core'
+import type { Connection, FlowProps, GraphEdge, GraphNode, VueFlowStore } from '~/types'
 
 const isDef = <T>(val: T): val is NonNullable<T> => typeof val !== 'undefined'
 export default (models: ToRefs<Pick<FlowProps, 'nodes' | 'edges' | 'modelValue'>>, props: FlowProps, store: VueFlowStore) => {
@@ -171,8 +172,45 @@ export default (models: ToRefs<Pick<FlowProps, 'nodes' | 'edges' | 'modelValue'>
       })
     }
 
+    const watchAutoConnect = () => {
+      scope.run(() => {
+        watch(
+          () => props.autoConnect,
+          () => {
+            if (isDef(props.autoConnect)) {
+              store.autoConnect.value = props.autoConnect
+            }
+          },
+          { immediate: isDef(props.autoConnect) },
+        )
+
+        watch(
+          store.autoConnect,
+          () => {
+            const autoConnector = async (params: Connection) => {
+              let connect: boolean | Connection = true
+              if (isFunction(props.autoConnect)) {
+                connect = await props.autoConnect(params)
+              }
+
+              if (connect) {
+                store.addEdges([params])
+              }
+            }
+
+            if (store.autoConnect) {
+              store.onConnect(autoConnector)
+            } else {
+              store.hooks.value.connect.off(autoConnector)
+            }
+          },
+          { immediate: true },
+        )
+      })
+    }
+
     const watchRest = () => {
-      const skip = ['id', 'modelValue', 'edges', 'nodes', 'maxZoom', 'minZoom', 'applyDefault']
+      const skip = ['id', 'modelValue', 'edges', 'nodes', 'maxZoom', 'minZoom', 'applyDefault', 'autoConnect']
       Object.keys(props).forEach((prop) => {
         if (!skip.includes(prop)) {
           const model = props[prop as keyof typeof props]
@@ -193,9 +231,16 @@ export default (models: ToRefs<Pick<FlowProps, 'nodes' | 'edges' | 'modelValue'>
       })
     }
 
-    ;[watchModelValue, watchNodesValue, watchEdgesValue, watchMinZoom, watchMaxZoom, watchApplyDefault, watchRest].forEach(
-      (watch) => watch(),
-    )
+    ;[
+      watchModelValue,
+      watchNodesValue,
+      watchEdgesValue,
+      watchMinZoom,
+      watchMaxZoom,
+      watchApplyDefault,
+      watchAutoConnect,
+      watchRest,
+    ].forEach((watch) => watch())
   })
 
   return () => scope.stop()

packages/vue-flow/src/store/state.ts

@@ -101,6 +101,7 @@ const defaultState = (): State => ({
   hooks: createHooks(),
 
   applyDefault: true,
+  autoConnect: false,
 
   fitViewOnInit: false,
   noDragClassName: 'nodrag',

packages/vue-flow/src/types/connection.ts

@@ -2,6 +2,7 @@ import type { CSSProperties } from 'vue'
 import type { Position } from './flow'
 import type { GraphNode } from './node'
 import type { HandleElement, HandleType } from './handle'
+import type { Edge } from './edge'
 
 /** Connection line types (same as default edge types */
 export enum ConnectionLineType {
@@ -23,6 +24,10 @@ export interface Connection {
   targetHandle: string | null
 }
 
+export type Connector = (
+  params: Connection,
+) => Promise<(Connection & Partial<Edge>) | false> | ((Connection & Partial<Edge>) | false)
+
 /** The source nodes params when connection is initiated */
 export interface OnConnectStartParams {
   /** Source node id */

packages/vue-flow/src/types/flow.ts

@@ -1,7 +1,7 @@
 import type { CSSProperties } from 'vue'
 import type { DefaultEdgeOptions, Edge, GraphEdge } from './edge'
 import type { CoordinateExtent, GraphNode, Node } from './node'
-import type { ConnectionLineType, ConnectionMode } from './connection'
+import type { ConnectionLineType, ConnectionMode, Connector } from './connection'
 import type { KeyCode, PanOnScrollMode } from './zoom'
 import type { DefaultEdgeTypes, DefaultNodeTypes, EdgeComponent, NodeComponent } from './components'
 
@@ -122,6 +122,8 @@ export interface FlowProps {
   connectOnClick?: boolean
   /** apply default change handlers for position, dimensions, adding/removing nodes. set this to false if you want to apply the changes manually */
   applyDefault?: boolean
+  /** automatically create an edge when connection is triggered */
+  autoConnect?: boolean | Connector
   noDragClassName?: string
   noWheelClassName?: string
   noPanClassName?: string

packages/vue-flow/src/types/store.ts

@@ -1,7 +1,7 @@
 import type { CSSProperties, ComputedRef, ToRefs } from 'vue'
 import type { Dimensions, ElementData, Elements, FlowElements, FlowExportObject, FlowOptions, SnapGrid, XYPosition } from './flow'
 import type { DefaultEdgeTypes, DefaultNodeTypes, EdgeComponent, NodeComponent } from './components'
-import type { Connection, ConnectionLineType, ConnectionMode } from './connection'
+import type { Connection, ConnectionLineType, ConnectionMode, Connector } from './connection'
 import type { DefaultEdgeOptions, Edge, GraphEdge } from './edge'
 import type { CoordinateExtent, GraphNode, Node } from './node'
 import type { D3Selection, D3Zoom, D3ZoomHandler, KeyCode, PanOnScrollMode, Viewport, ViewportFunctions } from './zoom'
@@ -88,6 +88,7 @@ export interface State extends Omit<FlowOptions, 'id' | 'modelValue'> {
 
   initialized: boolean
   applyDefault: boolean
+  autoConnect: boolean | Connector
 
   fitViewOnInit?: boolean