Remove PrefixContext

Author: penelopeysm

HISTORY.md

@@ -4,6 +4,10 @@
 
 Removed the method `returned(::Model, values, keys)`; please use `returned(::Model, ::AbstractDict{<:VarName})` instead.
 
+### Breaking changes
+
+`PrefixContext` is removed, etc., etc.... (I'll write this if I actually have to)
+
 ## 0.38.4
 
 Improve performance of VarNamedVector. It should now be very nearly on par with Metadata for all models we've benchmarked on.

docs/src/api.md

@@ -467,7 +467,6 @@ Contexts are subtypes of `AbstractPPL.AbstractContext`.
 
 ```@docs
 DefaultContext
-PrefixContext
 ConditionContext
 InitContext
 ```

src/DynamicPPL.jl

@@ -97,7 +97,6 @@ export AbstractVarInfo,
     # Contexts
     contextualize,
     DefaultContext,
-    PrefixContext,
     ConditionContext,
     # Tilde pipeline
     tilde_assume!!,
@@ -174,9 +173,9 @@ include("contexts.jl")
 include("contexts/default.jl")
 include("contexts/init.jl")
 include("contexts/transformation.jl")
-include("contexts/prefix.jl")
-include("contexts/conditionfix.jl")  # Must come after contexts/prefix.jl
+include("contexts/conditionfix.jl")
 include("model.jl")
+include("prefix.jl")
 include("varname.jl")
 include("distribution_wrappers.jl")
 include("submodel.jl")

src/compiler.jl

@@ -42,7 +42,7 @@ function make_varname_expression(expr)
 end
 
 """
-    isassumption(expr[, vn])
+    isassumption(expr[, left_vn])
 
 Return an expression that can be evaluated to check if `expr` is an assumption in the
 model.
@@ -55,16 +55,19 @@ Let `expr` be `:(x[1])`. It is an assumption in the following cases:
 
 When `expr` is not an expression or symbol (i.e., a literal), this expands to `false`.
 
-If `vn` is specified, it will be assumed to refer to a expression which
+If `left_vn` is specified, it will be assumed to refer to a expression which
 evaluates to a `VarName`, and this will be used in the subsequent checks.
-If `vn` is not specified, `AbstractPPL.varname(expr, need_concretize(expr))` will be
+If `left_vn` is not specified, `AbstractPPL.varname(expr, need_concretize(expr))` will be
 used in its place.
 """
-function isassumption(expr::Union{Expr,Symbol}, vn=make_varname_expression(expr))
+function isassumption(expr::Union{Expr,Symbol}, left_vn=make_varname_expression(expr))
+    @gensym vn
     return quote
-        if $(DynamicPPL.contextual_isassumption)(
-            __model__.context, $(DynamicPPL.prefix)(__model__.context, $vn)
-        )
+        # TODO(penelopeysm): This re-prefixing seems a bit wasteful. I'd really like
+        # the whole `isassumption` thing to be simplified, though, so I'll
+        # leave it till later.
+        $vn = $(DynamicPPL.maybe_prefix)($left_vn, __model__.prefix)
+        if $(DynamicPPL.contextual_isassumption)(__model__.context, $vn)
             # Considered an assumption by `__model__.context` which means either:
             # 1. We hit the default implementation, e.g. using `DefaultContext`,
             #    which in turn means that we haven't considered if it's one of
@@ -78,8 +81,8 @@ function isassumption(expr::Union{Expr,Symbol}, vn=make_varname_expression(expr)
             #    TODO: Support by adding context to model, and use `model.args`
             #    as the default conditioning. Then we no longer need to check `inargnames`
             #    since it will all be handled by `contextual_isassumption`.
-            if !($(DynamicPPL.inargnames)($vn, __model__)) ||
-                $(DynamicPPL.inmissings)($vn, __model__)
+            if !($(DynamicPPL.inargnames)($left_vn, __model__)) ||
+                $(DynamicPPL.inmissings)($left_vn, __model__)
                 true
             else
                 $(maybe_view(expr)) === missing
@@ -99,7 +102,7 @@ isassumption(expr) = :(false)
 
 Return `true` if `vn` is considered an assumption by `context`.
 """
-function contextual_isassumption(context::AbstractContext, vn)
+function contextual_isassumption(context::AbstractContext, vn::VarName)
     if hasconditioned_nested(context, vn)
         val = getconditioned_nested(context, vn)
         # TODO: Do we even need the `>: Missing`, i.e. does it even help the compiler?
@@ -115,9 +118,7 @@ end
 
 isfixed(expr, vn) = false
 function isfixed(::Union{Symbol,Expr}, vn)
-    return :($(DynamicPPL.contextual_isfixed)(
-        __model__.context, $(DynamicPPL.prefix)(__model__.context, $vn)
-    ))
+    return :($(DynamicPPL.contextual_isfixed)(__model__.context, $vn))
 end
 
 """
@@ -413,7 +414,9 @@ function generate_assign(left, right)
     return quote
         $right_val = $right
         if $(DynamicPPL.is_extracting_values)(__varinfo__)
-            $vn = $(DynamicPPL.prefix)(__model__.context, $(make_varname_expression(left)))
+            $vn = $(DynamicPPL.maybe_prefix)(
+                $(make_varname_expression(left)), __model__.prefix
+            )
             __varinfo__ = $(map_accumulator!!)(
                 $acc -> push!($acc, $vn, $right_val), __varinfo__, Val(:ValuesAsInModel)
             )
@@ -448,24 +451,23 @@ function generate_tilde(left, right)
 
     # Otherwise it is determined by the model or its value,
     # if the LHS represents an observation
-    @gensym vn isassumption value dist
+    @gensym left_vn vn isassumption value dist
 
     return quote
         $dist = $right
-        $vn = $(DynamicPPL.resolve_varnames)($(make_varname_expression(left)), $dist)
-        $isassumption = $(DynamicPPL.isassumption(left, vn))
+        $left_vn = $(DynamicPPL.resolve_varnames)($(make_varname_expression(left)), $dist)
+        $vn = $(DynamicPPL.maybe_prefix)($left_vn, __model__.prefix)
+        $isassumption = $(DynamicPPL.isassumption(left, left_vn))
         if $(DynamicPPL.isfixed(left, vn))
-            $left = $(DynamicPPL.getfixed_nested)(
-                __model__.context, $(DynamicPPL.prefix)(__model__.context, $vn)
-            )
+            $left = $(DynamicPPL.getfixed_nested)(__model__.context, $vn)
         elseif $isassumption
             $(generate_tilde_assume(left, dist, vn))
         else
-            # If `vn` is not in `argnames`, we need to make sure that the variable is defined.
-            if !$(DynamicPPL.inargnames)($vn, __model__)
-                $left = $(DynamicPPL.getconditioned_nested)(
-                    __model__.context, $(DynamicPPL.prefix)(__model__.context, $vn)
-                )
+            # If `left_vn` is not in `argnames`, we need to make sure that the variable is defined.
+            # (Note: we use the unprefixed `left_vn` here rather than `vn` which will have had
+            # prefixes applied!)
+            if !$(DynamicPPL.inargnames)($left_vn, __model__)
+                $left = $(DynamicPPL.getconditioned_nested)(__model__.context, $vn)
             end
 
             $value, __varinfo__ = $(DynamicPPL.tilde_observe!!)(
@@ -495,6 +497,7 @@ function generate_tilde_assume(left, right, vn)
     return quote
         $value, __varinfo__ = $(DynamicPPL.tilde_assume!!)(
             __model__.context,
+            __model__.prefix,
             $(DynamicPPL.unwrap_right_vn)($(DynamicPPL.check_tilde_rhs)($right), $vn)...,
             __varinfo__,
         )

src/contexts.jl

@@ -123,6 +123,7 @@ setleafcontext(::IsLeaf, ::IsLeaf, left::AbstractContext, right::AbstractContext
 """
     DynamicPPL.tilde_assume!!(
         context::AbstractContext,
+        prefix::Union{VarName,Nothing},
         right::Distribution,
         vn::VarName,
         vi::AbstractVarInfo
@@ -134,13 +135,21 @@ sampled value and updated `vi`.
 
 `vn` is the VarName on the left-hand side of the tilde statement.
 
+`prefix` is the currently active prefix; this is `nothing` if there is no active prefix.
+For example, in `a ~ to_submodel(inner_model)`, when executing `inner_model`, the active
+prefix will be `@varname(a)`.
+
 This function should return a tuple `(x, vi)`, where `x` is the sampled value (which
 must be in unlinked space!) and `vi` is the updated VarInfo.
 """
 function tilde_assume!!(
-    context::AbstractContext, right::Distribution, vn::VarName, vi::AbstractVarInfo
+    context::AbstractContext,
+    prefix::Union{VarName,Nothing},
+    right::Distribution,
+    vn::VarName,
+    vi::AbstractVarInfo,
 )
-    return tilde_assume!!(childcontext(context), right, vn, vi)
+    return tilde_assume!!(childcontext(context), prefix, right, vn, vi)
 end
 
 """

src/contexts/conditionfix.jl

@@ -83,9 +83,6 @@ hasconditioned_nested(::IsLeaf, context, vn) = hasconditioned(context, vn)
 function hasconditioned_nested(::IsParent, context, vn)
     return hasconditioned(context, vn) || hasconditioned_nested(childcontext(context), vn)
 end
-function hasconditioned_nested(context::PrefixContext, vn)
-    return hasconditioned_nested(collapse_prefix_stack(context), vn)
-end
 
 """
     getconditioned_nested(context, vn)
@@ -101,9 +98,6 @@ end
 function getconditioned_nested(::IsLeaf, context, vn)
     return error("context $(context) does not contain value for $vn")
 end
-function getconditioned_nested(context::PrefixContext, vn)
-    return getconditioned_nested(collapse_prefix_stack(context), vn)
-end
 function getconditioned_nested(::IsParent, context, vn)
     return if hasconditioned(context, vn)
         getconditioned(context, vn)
@@ -172,9 +166,6 @@ function conditioned(context::ConditionContext)
     # precedence over decendants of `context`.
     return _merge(context.values, conditioned(childcontext(context)))
 end
-function conditioned(context::PrefixContext)
-    return conditioned(collapse_prefix_stack(context))
-end
 
 struct FixedContext{Values,Ctx<:AbstractContext} <: AbstractContext
     values::Values
@@ -237,9 +228,6 @@ hasfixed_nested(::IsLeaf, context, vn) = hasfixed(context, vn)
 function hasfixed_nested(::IsParent, context, vn)
     return hasfixed(context, vn) || hasfixed_nested(childcontext(context), vn)
 end
-function hasfixed_nested(context::PrefixContext, vn)
-    return hasfixed_nested(collapse_prefix_stack(context), vn)
-end
 
 """
     getfixed_nested(context, vn)
@@ -255,9 +243,6 @@ end
 function getfixed_nested(::IsLeaf, context, vn)
     return error("context $(context) does not contain value for $vn")
 end
-function getfixed_nested(context::PrefixContext, vn)
-    return getfixed_nested(collapse_prefix_stack(context), vn)
-end
 function getfixed_nested(::IsParent, context, vn)
     return if hasfixed(context, vn)
         getfixed(context, vn)
@@ -351,117 +336,3 @@ function fixed(context::FixedContext)
     # precedence over decendants of `context`.
     return _merge(context.values, fixed(childcontext(context)))
 end
-function fixed(context::PrefixContext)
-    return fixed(collapse_prefix_stack(context))
-end
-
-###########################################################################
-### Interaction of PrefixContext with ConditionContext and FixedContext ###
-###########################################################################
-
-"""
-    collapse_prefix_stack(context::AbstractContext)
-
-Apply `PrefixContext`s to any conditioned or fixed values inside them, and remove
-the `PrefixContext`s from the context stack.
-
-!!! note
-    If you are reading this docstring, you might probably be interested in a more
-thorough explanation of how PrefixContext and ConditionContext / FixedContext
-interact with one another, especially in the context of submodels.
-    The DynamicPPL documentation contains [a separate page on this
-topic](https://turinglang.org/DynamicPPL.jl/previews/PR892/internals/submodel_condition/)
-which explains this in much more detail.
-
-```jldoctest
-julia> using DynamicPPL: collapse_prefix_stack
-
-julia> c1 = PrefixContext(@varname(a), ConditionContext((x=1, )));
-
-julia> collapse_prefix_stack(c1)
-ConditionContext(Dict(a.x => 1), DefaultContext())
-
-julia> # Here, `x` gets prefixed only with `a`, whereas `y` is prefixed with both.
-       c2 = PrefixContext(@varname(a), ConditionContext((x=1, ), PrefixContext(@varname(b), ConditionContext((y=2,)))));
-
-julia> collapsed = collapse_prefix_stack(c2);
-
-julia> # `collapsed` really looks something like this:
-       # ConditionContext(Dict{VarName{:a}, Int64}(a.b.y => 2, a.x => 1), DefaultContext())
-       # To avoid fragility arising from the order of the keys in the doctest, we test
-       # this indirectly:
-       collapsed.values[@varname(a.x)], collapsed.values[@varname(a.b.y)]
-(1, 2)
-```
-"""
-function collapse_prefix_stack(context::PrefixContext)
-    # Collapse the child context (thus applying any inner prefixes first)
-    collapsed = collapse_prefix_stack(childcontext(context))
-    # Prefix any conditioned variables with the current prefix
-    # Note: prefix_conditioned_variables is O(N) in the depth of the context stack.
-    # So is this function. In the worst case scenario, this is O(N^2) in the
-    # depth of the context stack.
-    return prefix_cond_and_fixed_variables(collapsed, context.vn_prefix)
-end
-function collapse_prefix_stack(context::AbstractContext)
-    return collapse_prefix_stack(NodeTrait(collapse_prefix_stack, context), context)
-end
-collapse_prefix_stack(::IsLeaf, context) = context
-function collapse_prefix_stack(::IsParent, context)
-    new_child_context = collapse_prefix_stack(childcontext(context))
-    return setchildcontext(context, new_child_context)
-end
-
-"""
-    prefix_cond_and_fixed_variables(context::AbstractContext, prefix::VarName)
-
-Prefix all the conditioned and fixed variables in a given context with a single
-`prefix`.
-
-```jldoctest
-julia> using DynamicPPL: prefix_cond_and_fixed_variables, ConditionContext
-
-julia> c1 = ConditionContext((a=1, ))
-ConditionContext((a = 1,), DefaultContext())
-
-julia> prefix_cond_and_fixed_variables(c1, @varname(y))
-ConditionContext(Dict(y.a => 1), DefaultContext())
-```
-"""
-function prefix_cond_and_fixed_variables(ctx::ConditionContext, prefix::VarName)
-    # Replace the prefix of the conditioned variables
-    vn_dict = to_varname_dict(ctx.values)
-    prefixed_vn_dict = Dict(
-        AbstractPPL.prefix(vn, prefix) => value for (vn, value) in vn_dict
-    )
-    # Prefix the child context as well
-    prefixed_child_ctx = prefix_cond_and_fixed_variables(childcontext(ctx), prefix)
-    return ConditionContext(prefixed_vn_dict, prefixed_child_ctx)
-end
-function prefix_cond_and_fixed_variables(ctx::FixedContext, prefix::VarName)
-    # Replace the prefix of the conditioned variables
-    vn_dict = to_varname_dict(ctx.values)
-    prefixed_vn_dict = Dict(
-        AbstractPPL.prefix(vn, prefix) => value for (vn, value) in vn_dict
-    )
-    # Prefix the child context as well
-    prefixed_child_ctx = prefix_cond_and_fixed_variables(childcontext(ctx), prefix)
-    return FixedContext(prefixed_vn_dict, prefixed_child_ctx)
-end
-function prefix_cond_and_fixed_variables(c::AbstractContext, prefix::VarName)
-    return prefix_cond_and_fixed_variables(
-        NodeTrait(prefix_cond_and_fixed_variables, c), c, prefix
-    )
-end
-function prefix_cond_and_fixed_variables(
-    ::IsLeaf, context::AbstractContext, prefix::VarName
-)
-    return context
-end
-function prefix_cond_and_fixed_variables(
-    ::IsParent, context::AbstractContext, prefix::VarName
-)
-    return setchildcontext(
-        context, prefix_cond_and_fixed_variables(childcontext(context), prefix)
-    )
-end

src/contexts/default.jl

@@ -21,14 +21,22 @@ NodeTrait(::DefaultContext) = IsLeaf()
 
 """
     DynamicPPL.tilde_assume!!(
-        ::DefaultContext, right::Distribution, vn::VarName, vi::AbstractVarInfo
+        ::DefaultContext,
+        prefix::Union{VarName,Nothing},
+        right::Distribution,
+        vn::VarName,
+        vi::AbstractVarInfo
     )
 
 Handle assumed variables. For `DefaultContext`, this function extracts the value associated
 with `vn` from `vi`, If `vi` does not contain an appropriate value then this will error.
 """
 function tilde_assume!!(
-    ::DefaultContext, right::Distribution, vn::VarName, vi::AbstractVarInfo
+    ::DefaultContext,
+    ::Union{VarName,Nothing},
+    right::Distribution,
+    vn::VarName,
+    vi::AbstractVarInfo,
 )
     y = getindex_internal(vi, vn)
     f = from_maybe_linked_internal_transform(vi, vn, right)

src/contexts/init.jl

@@ -153,7 +153,11 @@ end
 NodeTrait(::InitContext) = IsLeaf()
 
 function tilde_assume!!(
-    ctx::InitContext, dist::Distribution, vn::VarName, vi::AbstractVarInfo
+    ctx::InitContext,
+    ::Union{VarName,Nothing},
+    dist::Distribution,
+    vn::VarName,
+    vi::AbstractVarInfo,
 )
     in_varinfo = haskey(vi, vn)
     # `init()` always returns values in original space, i.e. possibly