Merge pull request #4087 from node-red/junction-loops

Prevent loops being created with junction nodes
node-red · Mar 2, 2023 · 40b506b · 40b506b
2 parents b19a679 + 81d4c60
commit 40b506b
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Showing 3 changed files with 27 additions and 4 deletions.
diff --git a/packages/node_modules/@node-red/editor-client/src/js/nodes.js b/packages/node_modules/@node-red/editor-client/src/js/nodes.js
@@ -1090,6 +1090,11 @@ RED.nodes = (function() {
         return false;
     }
 
+    function getDownstreamNodes(node) {
+        const downstreamLinks = nodeLinks[node.id].out
+        const downstreamNodes = new Set(downstreamLinks.map(l => l.target))
+        return Array.from(downstreamNodes)
+    }
     function getAllDownstreamNodes(node) {
         return getAllFlowNodes(node,'down').filter(function(n) { return n !== node });
     }
@@ -3086,6 +3091,7 @@ RED.nodes = (function() {
         getAllFlowNodes: getAllFlowNodes,
         getAllUpstreamNodes: getAllUpstreamNodes,
         getAllDownstreamNodes: getAllDownstreamNodes,
+        getDownstreamNodes: getDownstreamNodes,
         getNodeIslands: getNodeIslands,
         createExportableNodeSet: createExportableNodeSet,
         createCompleteNodeSet: createCompleteNodeSet,

diff --git a/packages/node_modules/@node-red/editor-client/src/js/ui/contextMenu.js b/packages/node_modules/@node-red/editor-client/src/js/ui/contextMenu.js
@@ -82,15 +82,15 @@ RED.contextMenu = (function () {
                             dirty: true,
                             moved: true
                         }
+                        const junction = RED.nodes.addJunction(nn);
                         const historyEvent = {
                             dirty: RED.nodes.dirty(),
                             t: 'add',
-                            junctions: [nn]
+                            junctions: [junction]
                         }
-                        RED.nodes.addJunction(nn);
                         RED.history.push(historyEvent);
                         RED.nodes.dirty(true);
-                        RED.view.select({nodes: [nn] });
+                        RED.view.select({nodes: [junction] });
                         RED.view.redraw(true)
                     },
                     disabled: !canEdit

diff --git a/packages/node_modules/@node-red/editor-client/src/js/ui/view.js b/packages/node_modules/@node-red/editor-client/src/js/ui/view.js
@@ -3095,8 +3095,25 @@ RED.view = (function() {
                             (drag_line.portType === PORT_TYPE_INPUT && mouseup_node.type === "subflow" && (mouseup_node.direction === "status" || mouseup_node.direction === "out")) ||
                             (drag_line.portType === PORT_TYPE_OUTPUT && mouseup_node.type === "subflow" && mouseup_node.direction === "in")
                         )) {
+                            let hasJunctionLoop = false
+                            if (link.source.type === 'junction' && link.target.type === 'junction') {
+                                // This is joining two junctions together. We want to avoid creating a loop
+                                // of pure junction nodes as there is no way to break out of it.
+
+                                const visited = new Set()
+                                let toVisit = [link.target]
+                                while (toVisit.length > 0) {
+                                    const next = toVisit.shift()
+                                    if (next === link.source) {
+                                        hasJunctionLoop = true
+                                        break
+                                    }
+                                    visited.add(next)
+                                    toVisit = toVisit.concat(RED.nodes.getDownstreamNodes(next).filter(n => n.type === 'junction' && !visited.has(n)))
+                                }
+                            }
                             var existingLink = RED.nodes.filterLinks({source:src,target:dst,sourcePort: src_port}).length !== 0;
-                            if (!existingLink) {
+                            if (!hasJunctionLoop && !existingLink) {
                                 RED.nodes.addLink(link);
                                 addedLinks.push(link);
                             }