[core/ui] Graph: The graph now use a DAGVisitor to avoid cyclic dependency connection

Author: nicolas-lambert-tc

meshroom/core/exception.py

@@ -64,3 +64,8 @@ class StopGraphVisit(GraphVisitMessage):
 class StopBranchVisit(GraphVisitMessage):
     """ Immediately stop branch visit. """
     pass
+
+
+class CyclicDependencyError(Exception):
+    """ Raised if a cyclic dependency is find in a DAG graph """
+    pass

meshroom/core/graph.py

@@ -15,7 +15,7 @@
 from meshroom.common import BaseObject, DictModel, Slot, Signal, Property
 from meshroom.core import Version
 from meshroom.core.attribute import Attribute, ListAttribute, GroupAttribute
-from meshroom.core.exception import GraphCompatibilityError, InvalidEdgeError, StopGraphVisit, StopBranchVisit
+from meshroom.core.exception import GraphCompatibilityError, InvalidEdgeError, StopGraphVisit, StopBranchVisit, CyclicDependencyError
 from meshroom.core.graphIO import GraphIO, GraphSerializer, TemplateGraphSerializer, PartialGraphSerializer
 from meshroom.core.node import BaseNode, Status, Node, CompatibilityNode
 from meshroom.core.nodeFactory import nodeFactory
@@ -134,6 +134,14 @@ def finishVertex(self, u, g):
         pass
 
 
+class DAGVisitor(Visitor):
+
+    def backEdge(self, e, g):
+        """ Is invoked on the back edges in the graph. Means that there is a cyclic dependency in the visited graph """
+
+        raise CyclicDependencyError("A cyclic dependency exists on the current DAG")
+
+
 def changeTopology(func):
     """
     Graph methods modifying the graph topology (add/remove edges or nodes)
@@ -889,7 +897,7 @@ def getRootNodes(self, dependenciesOnly):
         return set(self._nodes) - nodesWithInputLink
 
     @changeTopology
-    def addEdge(self, srcAttr: Attribute, dstAttr: Attribute):
+    def addEdge(self, srcAttr: Attribute, dstAttr: Attribute) -> "Edge":
         if not (srcAttr.node.graph == dstAttr.node.graph == self):
             raise InvalidEdgeError(
                 srcAttr.fullNameToGraph, dstAttr.fullNameToGraph, "Attributes do not belong to this Graph"
@@ -1030,7 +1038,7 @@ def dfsOnFinish(self, startNodes=None, longestPathFirst=False, reverse=False, de
         """
         nodes = []
         edges = []
-        visitor = Visitor(reverse=reverse, dependenciesOnly=dependenciesOnly)
+        visitor = DAGVisitor(reverse=reverse, dependenciesOnly=dependenciesOnly)
         visitor.finishVertex = lambda vertex, graph: nodes.append(vertex)
         visitor.finishEdge = lambda edge, graph: edges.append(edge)
         self.dfs(visitor=visitor, startNodes=startNodes, longestPathFirst=longestPathFirst)
@@ -1055,7 +1063,7 @@ def dfsOnDiscover(self, startNodes=None, filterTypes=None, longestPathFirst=Fals
         """
         nodes = []
         edges = []
-        visitor = Visitor(reverse=reverse, dependenciesOnly=dependenciesOnly)
+        visitor = DAGVisitor(reverse=reverse, dependenciesOnly=dependenciesOnly)
 
         def discoverVertex(vertex, graph):
             if not filterTypes or vertex.nodeType in filterTypes:
@@ -1079,7 +1087,7 @@ def dfsToProcess(self, startNodes=None):
         """
         nodes = []
         edges = []
-        visitor = Visitor(reverse=False, dependenciesOnly=True)
+        visitor = DAGVisitor(reverse=False, dependenciesOnly=True)
 
         def discoverVertex(vertex, graph):
             if vertex.hasStatus(Status.SUCCESS):
@@ -1135,7 +1143,7 @@ def updateNodesTopologicalData(self):
         self._computationBlocked.clear()
 
         compatNodes = []
-        visitor = Visitor(reverse=False, dependenciesOnly=False)
+        visitor = DAGVisitor(reverse=False, dependenciesOnly=False)
 
         def discoverVertex(vertex, graph):
             # initialize depths
@@ -1193,7 +1201,7 @@ def dfsMaxEdgeLength(self, startNodes=None, dependenciesOnly=True):
         """
         nodesStack = []
         edgesScore = defaultdict(int)
-        visitor = Visitor(reverse=False, dependenciesOnly=dependenciesOnly)
+        visitor = DAGVisitor(reverse=False, dependenciesOnly=dependenciesOnly)
 
         def finishEdge(edge, graph):
             u, v = edge
@@ -1276,7 +1284,7 @@ def canSubmitOrCompute(self, startNode):
         if startNode.isAlreadySubmittedOrFinished():
             return 0
 
-        class SCVisitor(Visitor):
+        class SCVisitor(DAGVisitor):
             def __init__(self, reverse, dependenciesOnly):
                 super().__init__(reverse, dependenciesOnly)
 

meshroom/ui/commands.py

@@ -6,6 +6,7 @@
 from PySide6.QtCore import Property, Signal
 
 from meshroom.core.attribute import ListAttribute, Attribute
+from meshroom.core.exception import CyclicDependencyError
 from meshroom.core.graph import Graph, GraphModification
 from meshroom.core.node import Position, CompatibilityIssue
 from meshroom.core.nodeFactory import nodeFactory
@@ -318,7 +319,13 @@ def __init__(self, graph, src, dst, parent=None):
             raise ValueError(f"Attribute are not compatible and cannot be connected: '{self.srcAttr}'({src.baseType})->'{self.dstAttr}'({dst.baseType})")
 
     def redoImpl(self):
-        self.graph.addEdge(self.graph.attribute(self.srcAttr), self.graph.attribute(self.dstAttr))
+
+        try:
+            self.graph.addEdge(self.graph.attribute(self.srcAttr), self.graph.attribute(self.dstAttr))
+        except CyclicDependencyError:
+            self.graph.removeEdge(self.graph.attribute(self.dstAttr))
+            return False
+        
         return True
 
     def undoImpl(self):