Add compile time keys for the extra properties of graph nodes

src/graph_engine.jl

@@ -537,6 +537,21 @@ hasextra(node::NodeData, key::Symbol) = haskey(node.extra, key)
 getextra(node::NodeData, key::Symbol) = getindex(node.extra, key)
 setextra!(node::NodeData, key::Symbol, value) = insert!(node.extra, key, value)
 
+"""
+A compile time key to access the `extra` properties of the `NodeData` structure.
+"""
+struct NodeDataExtraKey{K, T} end
+
+function hasextra(node::NodeData, key::NodeDataExtraKey{K}) where K 
+    return haskey(node.extra, K)
+end
+function getextra(node::NodeData, key::NodeDataExtraKey{K, T})::T where {K, T} 
+    return getindex(node.extra, K)::T
+end
+function setextra!(node::NodeData, key::NodeDataExtraKey{K}, value::T) where {K, T} 
+    return insert!(node.extra, K, value)
+end
+
 is_factor(node::NodeData)   = is_factor(getproperties(node))
 is_variable(node::NodeData) = is_variable(getproperties(node))
 

src/plugins/meta/meta_engine.jl

@@ -141,6 +141,8 @@ function apply_meta!(model::Model, context::Context, meta::MetaObject{S, T} wher
     end
 end
 
+const MetaExtraKey = NodeDataExtraKey{:meta, Any}()
+
 function save_meta!(model::Model, node::NodeLabel, meta::MetaObject{S, T} where {S, T <: NamedTuple})
     data = getmetainfo(meta)
     if !haskey(data, :meta)
@@ -155,7 +157,7 @@ end
 
 function save_meta!(model::Model, node::NodeLabel, meta::MetaObject{S, T} where {S, T})
     nodedata = model[node]
-    if !hasextra(nodedata, :meta)
-        setextra!(nodedata, :meta, getmetainfo(meta))
+    if !hasextra(nodedata, MetaExtraKey)
+        setextra!(nodedata, MetaExtraKey, getmetainfo(meta))
     end
 end

src/plugins/variational_constraints/variational_constraints_engine.jl

@@ -554,6 +554,8 @@ function materialize_constraints!(model::Model, node_label::NodeLabel, node_data
     return materialize_constraints!(model, node_label, node_data, getproperties(node_data))
 end
 
+const VariationalConstraintsFactorizationIndicesKey = NodeDataExtraKey{:factorization_constraint_indices, Tuple}()
+
 function materialize_constraints!(model::Model, node_label::NodeLabel, node_data::NodeData, ::FactorNodeProperties)
     constraint_bitset = getextra(node_data, :factorization_constraint_bitset)
     num_neighbors = length(constraint_bitset)
@@ -572,7 +574,7 @@ function materialize_constraints!(model::Model, node_label::NodeLabel, node_data
         )
     end
     rows = Tuple(map(row -> filter(!iszero, map(elem -> elem[2] == 1 ? elem[1] : 0, enumerate(row))), constraint_set))
-    setextra!(node_data, :factorization_constraint_indices, rows)
+    setextra!(node_data, VariationalConstraintsFactorizationIndicesKey, rows)
 end
 
 function is_valid_partition(contents)

test/graph_engine_tests.jl

@@ -101,6 +101,44 @@ end
     end
 end
 
+@testitem "NodeData extra properties" begin
+    import GraphPPL: create_model, getcontext, NodeData, FactorNodeProperties, VariableNodeProperties, getproperties, setextra!, getextra, hasextra, NodeDataExtraKey
+
+    model = create_model()
+    context = getcontext(model)
+
+    @testset for properties in (FactorNodeProperties(fform = String), VariableNodeProperties(name = :x, index = 1))
+        nodedata = NodeData(context, properties)
+
+        @test !hasextra(nodedata, :a)
+        setextra!(nodedata, :a, 1)
+        @test hasextra(nodedata, :a)
+        @test getextra(nodedata, :a) === 1
+
+        # In the current implementation it is not possible to update extra properties
+        @test_throws Exception setextra!(nodedata, :a, 2)
+
+        @test !hasextra(nodedata, :b)
+        setextra!(nodedata, :b, 2)
+        @test hasextra(nodedata, :b)
+        @test getextra(nodedata, :b) === 2
+
+        constkey_c_float = NodeDataExtraKey{:c, Float64}()
+
+        @test !@inferred(hasextra(nodedata, constkey_c_float))
+        @inferred(setextra!(nodedata, constkey_c_float, 3.0))
+        @test @inferred(hasextra(nodedata, constkey_c_float))
+        @test @inferred(getextra(nodedata, constkey_c_float)) === 3.0
+
+        constkey_d_int = NodeDataExtraKey{:d, Int64}()
+
+        @test !@inferred(hasextra(nodedata, constkey_d_int))
+        @inferred(setextra!(nodedata, constkey_d_int, 4))
+        @test @inferred(hasextra(nodedata, constkey_d_int))
+        @test @inferred(getextra(nodedata, constkey_d_int)) === 4
+    end
+end
+
 @testitem "factor_nodes" begin
     import GraphPPL: factor_nodes, is_factor, labels
     include("model_zoo.jl")