[core] Graph: add importGraphContent API

Extract the logic of importing the content of a graph within a graph instance from
the graph loading logic.
Add `Graph.importGraphContent` and `Graph.importGraphContentFromFile`
methods.
Use the deserialization API to load the content in another temporary graph instance,
to handle the renaming of nodes using the Graph API, rather than manipulating
entries in a raw dictionnary.

tests/test_graphIO.py

@@ -0,0 +1,152 @@
+from meshroom.core import desc
+from meshroom.core.graph import Graph
+
+from .utils import registeredNodeTypes
+
+
+class SimpleNode(desc.Node):
+    inputs = [
+        desc.File(name="input", label="Input", description="", value=""),
+    ]
+    outputs = [
+        desc.File(name="output", label="Output", description="", value=""),
+    ]
+
+
+def compareGraphsContent(graphA: Graph, graphB: Graph) -> bool:
+    """Returns whether the content (node and deges) of two graphs are considered identical.
+
+    Similar nodes: nodes with the same name, type and compatibility status.
+    Similar edges: edges with the same source and destination attribute names.
+    """
+
+    def _buildNodesSet(graph: Graph):
+        return set([(node.name, node.nodeType, node.isCompatibilityNode) for node in graph.nodes])
+
+    def _buildEdgesSet(graph: Graph):
+        return set([(edge.src.fullName, edge.dst.fullName) for edge in graph.edges])
+
+    return _buildNodesSet(graphA) == _buildNodesSet(graphB) and _buildEdgesSet(graphA) == _buildEdgesSet(
+        graphB
+    )
+
+
+class TestImportGraphContent:
+    def test_importEmptyGraph(self):
+        graph = Graph("")
+
+        otherGraph = Graph("")
+        nodes = otherGraph.importGraphContent(graph)
+
+        assert len(nodes) == 0
+        assert len(graph.nodes) == 0
+
+    def test_importGraphWithSingleNode(self):
+        graph = Graph("")
+
+        with registeredNodeTypes([SimpleNode]):
+            graph.addNewNode(SimpleNode.__name__)
+
+            otherGraph = Graph("")
+            otherGraph.importGraphContent(graph)
+
+            assert compareGraphsContent(graph, otherGraph)
+
+    def test_importGraphWithSeveralNodes(self):
+        graph = Graph("")
+
+        with registeredNodeTypes([SimpleNode]):
+            graph.addNewNode(SimpleNode.__name__)
+            graph.addNewNode(SimpleNode.__name__)
+
+            otherGraph = Graph("")
+            otherGraph.importGraphContent(graph)
+
+            assert compareGraphsContent(graph, otherGraph)
+
+    def test_importingGraphWithNodesAndEdges(self):
+        graph = Graph("")
+
+        with registeredNodeTypes([SimpleNode]):
+            nodeA_1 = graph.addNewNode(SimpleNode.__name__)
+            nodeA_2 = graph.addNewNode(SimpleNode.__name__)
+
+            graph.addEdge(nodeA_1.output, nodeA_2.input)
+
+            otherGraph = Graph("")
+            otherGraph.importGraphContent(graph)
+            assert compareGraphsContent(graph, otherGraph)
+
+    def test_edgeRemappingOnImportingGraphSeveralTimes(self):
+        graph = Graph("")
+
+        with registeredNodeTypes([SimpleNode]):
+            nodeA_1 = graph.addNewNode(SimpleNode.__name__)
+            nodeA_2 = graph.addNewNode(SimpleNode.__name__)
+
+            graph.addEdge(nodeA_1.output, nodeA_2.input)
+
+            otherGraph = Graph("")
+            otherGraph.importGraphContent(graph)
+            otherGraph.importGraphContent(graph)
+
+    def test_importGraphWithUnknownNodeTypesCreatesCompatibilityNodes(self):
+        graph = Graph("")
+
+        with registeredNodeTypes([SimpleNode]):
+            graph.addNewNode(SimpleNode.__name__)
+
+        otherGraph = Graph("")
+        importedNode = otherGraph.importGraphContent(graph)
+
+        assert len(importedNode) == 1
+        assert importedNode[0].isCompatibilityNode
+
+    def test_importGraphContentInPlace(self):
+        graph = Graph("")
+
+        with registeredNodeTypes([SimpleNode]):
+            nodeA_1 = graph.addNewNode(SimpleNode.__name__)
+            nodeA_2 = graph.addNewNode(SimpleNode.__name__)
+
+            graph.addEdge(nodeA_1.output, nodeA_2.input)
+
+            graph.importGraphContent(graph)
+
+            assert len(graph.nodes) == 4
+
+    def test_importGraphContentFromFile(self, graphSavedOnDisk):
+        graph: Graph = graphSavedOnDisk
+
+        with registeredNodeTypes([SimpleNode]):
+            nodeA_1 = graph.addNewNode(SimpleNode.__name__)
+            nodeA_2 = graph.addNewNode(SimpleNode.__name__)
+
+            graph.addEdge(nodeA_1.output, nodeA_2.input)
+            graph.save()
+
+            otherGraph = Graph("")
+            nodes = otherGraph.importGraphContentFromFile(graph.filepath)
+
+            assert len(nodes) == 2
+
+            assert compareGraphsContent(graph, otherGraph)
+
+    def test_importGraphContentFromFileWithCompatibilityNodes(self, graphSavedOnDisk):
+        graph: Graph = graphSavedOnDisk
+
+        with registeredNodeTypes([SimpleNode]):
+            nodeA_1 = graph.addNewNode(SimpleNode.__name__)
+            nodeA_2 = graph.addNewNode(SimpleNode.__name__)
+
+            graph.addEdge(nodeA_1.output, nodeA_2.input)
+            graph.save()
+
+        otherGraph = Graph("")
+        nodes = otherGraph.importGraphContentFromFile(graph.filepath)
+
+        assert len(nodes) == 2
+        assert len(otherGraph.compatibilityNodes) == 2
+        assert not compareGraphsContent(graph, otherGraph)
+
+