[graphIO] Introduce graph serializer classes

Move the serialization logic to dedicated serializer classes.
Implement both `GraphSerializer` and `TemplateGraphSerializer`
to cover for the existing serialization use-cases.

meshroom/core/graph.py

@@ -17,7 +17,7 @@ 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, StopGraphVisit, StopBranchVisit
-from meshroom.core.graphIO import GraphIO
+from meshroom.core.graphIO import GraphIO, GraphSerializer, TemplateGraphSerializer
 from meshroom.core.node import Status, Node, CompatibilityNode
 from meshroom.core.nodeFactory import nodeFactory
 from meshroom.core.typing import PathLike
@@ -1386,6 +1386,18 @@ class Graph(BaseObject):
     def asString(self):
         return str(self.toDict())
 
+    def serialize(self, asTemplate: bool = False) -> dict:
+        """Serialize this Graph instance.
+        
+        Args:
+            asTemplate: Whether to use the template serialization.
+
+        Returns:
+            The serialized graph data.
+        """
+        SerializerClass = TemplateGraphSerializer if asTemplate else GraphSerializer
+        return SerializerClass(self).serialize()
+
     def save(self, filepath=None, setupProjectFile=True, template=False):
         """
         Save the current Meshroom graph as a serialized ".mg" file.
@@ -1408,34 +1420,7 @@ class Graph(BaseObject):
         if not path:
             raise ValueError("filepath must be specified for unsaved files.")
 
-        self.header[GraphIO.Keys.ReleaseVersion] = meshroom.__version__
+        data = self.serialize(template)
-        self.header[GraphIO.Keys.FileVersion] = GraphIO.__version__
-
-        # Store versions of node types present in the graph (excluding CompatibilityNode instances)
-        # and remove duplicates
-        usedNodeTypes = set([n.nodeDesc.__class__ for n in self._nodes if isinstance(n, Node)])
-        # Convert to node types to "name: version"
-        nodesVersions = {
-            "{}".format(p.__name__): meshroom.core.nodeVersion(p, "0.0")
-            for p in usedNodeTypes
-        }
-        # Sort them by name (to avoid random order changing from one save to another)
-        nodesVersions = dict(sorted(nodesVersions.items()))
-        # Add it the header
-        self.header[GraphIO.Keys.NodesVersions] = nodesVersions
-        self.header["template"] = template
-
-        data = {}
-        if template:
-            data = {
-                GraphIO.Keys.Header: self.header,
-                GraphIO.Keys.Graph: self.getNonDefaultInputAttributes()
-            }
-        else:
-            data = {
-                GraphIO.Keys.Header: self.header,
-                GraphIO.Keys.Graph: self.toDict()
-            }
 
         with open(path, 'w') as jsonFile:
             json.dump(data, jsonFile, indent=4)
@@ -1446,51 +1431,6 @@ class Graph(BaseObject):
         # update the file date version
         self._fileDateVersion = os.path.getmtime(path)
 
-    def getNonDefaultInputAttributes(self):
-        """
-        Instead of getting all the inputs and internal attribute keys, only get the keys of
-        the attributes whose value is not the default one.
-        The output attributes, UIDs, parallelization parameters and internal folder are
-        not relevant for templates, so they are explicitly removed from the returned dictionary.
-
-        Returns:
-            dict: self.toDict() with the output attributes, UIDs, parallelization parameters, internal folder
-            and input/internal attributes with default values removed
-        """
-        graph = self.toDict()
-        for nodeName in graph.keys():
-            node = self.node(nodeName)
-
-            inputKeys = list(graph[nodeName]["inputs"].keys())
-
-            internalInputKeys = []
-            internalInputs = graph[nodeName].get("internalInputs", None)
-            if internalInputs:
-                internalInputKeys = list(internalInputs.keys())
-
-            for attrName in inputKeys:
-                attribute = node.attribute(attrName)
-                # check that attribute is not a link for choice attributes
-                if attribute.isDefault and not attribute.isLink:
-                    del graph[nodeName]["inputs"][attrName]
-
-            for attrName in internalInputKeys:
-                attribute = node.internalAttribute(attrName)
-                # check that internal attribute is not a link for choice attributes
-                if attribute.isDefault and not attribute.isLink:
-                    del graph[nodeName]["internalInputs"][attrName]
-
-            # If all the internal attributes are set to their default values, remove the entry
-            if len(graph[nodeName]["internalInputs"]) == 0:
-                del graph[nodeName]["internalInputs"]
-
-            del graph[nodeName]["outputs"]
-            del graph[nodeName]["uid"]
-            del graph[nodeName]["internalFolder"]
-            del graph[nodeName]["parallelization"]
-
-        return graph
-
     def _setFilepath(self, filepath):
         """
         Set the internal filepath of this Graph.

meshroom/core/graphIO.py

@@ -1,7 +1,12 @@
 from enum import Enum
-from typing import Union
+from typing import Any, TYPE_CHECKING, Union
 
+import meshroom
 from meshroom.core import Version
+from meshroom.core.node import Node
+
+if TYPE_CHECKING:
+    from meshroom.core.graph import Graph
 
 
 class GraphIO:
@@ -54,3 +59,110 @@ class GraphIO:
 
         return tuple(features)
 
+
+class GraphSerializer:
+    """Standard Graph serializer."""
+
+    def __init__(self, graph: "Graph") -> None:
+        self._graph = graph
+
+    def serialize(self) -> dict:
+        """
+        Serialize the Graph.
+        """
+        return {
+            GraphIO.Keys.Header: self.serializeHeader(),
+            GraphIO.Keys.Graph: self.serializeContent(),
+        }
+
+    @property
+    def nodes(self) -> list[Node]:
+        return self._graph.nodes
+
+    def serializeHeader(self) -> dict:
+        """Build and return the graph serialization header.
+
+        The header contains metadata about the graph, such as the:
+            - version of the software used to create it.
+            - version of the file format.
+            - version of the nodes types used in the graph.
+            - template flag.
+
+        Args:
+            nodes: (optional) The list of nodes to consider for node types versions - use all nodes if not specified.
+            template: Whether the graph is going to be serialized as a template.
+        """
+        header: dict[str, Any] = {}
+        header[GraphIO.Keys.ReleaseVersion] = meshroom.__version__
+        header[GraphIO.Keys.FileVersion] = GraphIO.__version__
+        header[GraphIO.Keys.NodesVersions] = self._getNodeTypesVersions()
+        return header
+
+    def _getNodeTypesVersions(self) -> dict[str, str]:
+        """Get registered versions of each node types in `nodes`, excluding CompatibilityNode instances."""
+        nodeTypes = set([node.nodeDesc.__class__ for node in self.nodes if isinstance(node, Node)])
+        nodeTypesVersions = {
+            nodeType.__name__: meshroom.core.nodeVersion(nodeType, "0.0") for nodeType in nodeTypes
+        }
+        # Sort them by name (to avoid random order changing from one save to another).
+        return dict(sorted(nodeTypesVersions.items()))
+
+    def serializeContent(self) -> dict:
+        """Graph content serialization logic."""
+        return {node.name: self.serializeNode(node) for node in sorted(self.nodes, key=lambda n: n.name)}
+
+    def serializeNode(self, node: Node) -> dict:
+        """Node serialization logic."""
+        return node.toDict()
+
+
+class TemplateGraphSerializer(GraphSerializer):
+    """Serializer for serializing a graph as a template."""
+
+    def serializeHeader(self) -> dict:
+        header = super().serializeHeader()
+        header["template"] = True
+        return header
+
+    def serializeNode(self, node: Node) -> dict:
+        """Adapt node serialization to template graphs.
+        
+        Instead of getting all the inputs and internal attribute keys, only get the keys of
+        the attributes whose value is not the default one.
+        The output attributes, UIDs, parallelization parameters and internal folder are
+        not relevant for templates, so they are explicitly removed from the returned dictionary.
+        """
+        # For now, implemented as a post-process to update the default serialization.
+        nodeData = super().serializeNode(node)
+
+        inputKeys = list(nodeData["inputs"].keys())
+
+        internalInputKeys = []
+        internalInputs = nodeData.get("internalInputs", None)
+        if internalInputs:
+            internalInputKeys = list(internalInputs.keys())
+
+        for attrName in inputKeys:
+            attribute = node.attribute(attrName)
+            # check that attribute is not a link for choice attributes
+            if attribute.isDefault and not attribute.isLink:
+                del nodeData["inputs"][attrName]
+
+        for attrName in internalInputKeys:
+            attribute = node.internalAttribute(attrName)
+            # check that internal attribute is not a link for choice attributes
+            if attribute.isDefault and not attribute.isLink:
+                del nodeData["internalInputs"][attrName]
+
+        # If all the internal attributes are set to their default values, remove the entry
+        if len(nodeData["internalInputs"]) == 0:
+            del nodeData["internalInputs"]
+
+        del nodeData["outputs"]
+        del nodeData["uid"]
+        del nodeData["internalFolder"]
+        del nodeData["parallelization"]
+
+        return nodeData
+
+