Replace PriorExtractorContext with PriorDistributionAccumulator (#907)

Author: mhauru

src/extract_priors.jl

@@ -1,44 +1,47 @@
-struct PriorExtractorContext{D<:OrderedDict{VarName,Any},Ctx<:AbstractContext} <:
-       AbstractContext
+struct PriorDistributionAccumulator{D<:OrderedDict{VarName,Any}} <: AbstractAccumulator
     priors::D
-    context::Ctx
 end
 
-PriorExtractorContext(context) = PriorExtractorContext(OrderedDict{VarName,Any}(), context)
+PriorDistributionAccumulator() = PriorDistributionAccumulator(OrderedDict{VarName,Any}())
 
-NodeTrait(::PriorExtractorContext) = IsParent()
-childcontext(context::PriorExtractorContext) = context.context
-function setchildcontext(parent::PriorExtractorContext, child)
-    return PriorExtractorContext(parent.priors, child)
+accumulator_name(::PriorDistributionAccumulator) = :PriorDistributionAccumulator
+
+split(acc::PriorDistributionAccumulator) = PriorDistributionAccumulator(empty(acc.priors))
+function combine(acc1::PriorDistributionAccumulator, acc2::PriorDistributionAccumulator)
+    return PriorDistributionAccumulator(merge(acc1.priors, acc2.priors))
 end
 
-function setprior!(context::PriorExtractorContext, vn::VarName, dist::Distribution)
-    return context.priors[vn] = dist
+function setprior!(acc::PriorDistributionAccumulator, vn::VarName, dist::Distribution)
+    acc.priors[vn] = dist
+    return acc
 end
 
 function setprior!(
-    context::PriorExtractorContext, vns::AbstractArray{<:VarName}, dist::Distribution
+    acc::PriorDistributionAccumulator, vns::AbstractArray{<:VarName}, dist::Distribution
 )
     for vn in vns
-        context.priors[vn] = dist
+        acc.priors[vn] = dist
     end
+    return acc
 end
 
 function setprior!(
-    context::PriorExtractorContext,
+    acc::PriorDistributionAccumulator,
     vns::AbstractArray{<:VarName},
     dists::AbstractArray{<:Distribution},
 )
     for (vn, dist) in zip(vns, dists)
-        context.priors[vn] = dist
+        acc.priors[vn] = dist
     end
+    return acc
 end
 
-function DynamicPPL.tilde_assume(context::PriorExtractorContext, right, vn, vi)
-    setprior!(context, vn, right)
-    return DynamicPPL.tilde_assume(childcontext(context), right, vn, vi)
+function accumulate_assume!!(acc::PriorDistributionAccumulator, val, logjac, vn, right)
+    return setprior!(acc, vn, right)
 end
 
+accumulate_observe!!(acc::PriorDistributionAccumulator, right, left, vn) = acc
+
 """
     extract_priors([rng::Random.AbstractRNG, ]model::Model)
 
@@ -108,9 +111,13 @@ julia> length(extract_priors(rng, model)[@varname(x)])
 extract_priors(args::Union{Model,AbstractVarInfo}...) =
     extract_priors(Random.default_rng(), args...)
 function extract_priors(rng::Random.AbstractRNG, model::Model)
-    context = PriorExtractorContext(SamplingContext(rng))
-    evaluate!!(model, VarInfo(), context)
-    return context.priors
+    varinfo = VarInfo()
+    # TODO(mhauru) This doesn't actually need the NumProduceAccumulator, it's only a
+    # workaround for the fact that `order` is still hardcoded in VarInfo, and hence you
+    # can't push new variables without knowing the num_produce. Remove this when possible.
+    varinfo = setaccs!!(varinfo, (PriorDistributionAccumulator(), NumProduceAccumulator()))
+    varinfo = last(evaluate!!(model, varinfo, SamplingContext(rng)))
+    return getacc(varinfo, Val(:PriorDistributionAccumulator)).priors
 end
 
 """
@@ -122,7 +129,12 @@ This is done by evaluating the model at the values present in `varinfo`
 and recording the distributions that are present at each tilde statement.
 """
 function extract_priors(model::Model, varinfo::AbstractVarInfo)
-    context = PriorExtractorContext(DefaultContext())
-    evaluate!!(model, deepcopy(varinfo), context)
-    return context.priors
+    # TODO(mhauru) This doesn't actually need the NumProduceAccumulator, it's only a
+    # workaround for the fact that `order` is still hardcoded in VarInfo, and hence you
+    # can't push new variables without knowing the num_produce. Remove this when possible.
+    varinfo = setaccs!!(
+        deepcopy(varinfo), (PriorDistributionAccumulator(), NumProduceAccumulator())
+    )
+    varinfo = last(evaluate!!(model, varinfo, DefaultContext()))
+    return getacc(varinfo, Val(:PriorDistributionAccumulator)).priors
 end