Allow to provide RNG only in model evaluation (#172)

Addresses TuringLang/Turing.jl#1421 (comment).

Author: devmotion

Project.toml

@@ -1,6 +1,6 @@
 name = "DynamicPPL"
 uuid = "366bfd00-2699-11ea-058f-f148b4cae6d8"
-version = "0.9.2"
+version = "0.9.3"
 
 [deps]
 AbstractMCMC = "80f14c24-f653-4e6a-9b94-39d6b0f70001"

src/model.jl

@@ -76,26 +76,35 @@ Sample from the `model` using the `sampler` with random number generator `rng` a
 The method resets the log joint probability of `varinfo` and increases the evaluation
 number of `sampler`.
 """
-function (model::Model)(args...)
-    return model(VarInfo(), args...)
-end
-
-function (model::Model)(varinfo::AbstractVarInfo, args...)
-    return model(Random.GLOBAL_RNG, varinfo, args...)
-end
-
 function (model::Model)(
     rng::Random.AbstractRNG,
-    varinfo::AbstractVarInfo,
+    varinfo::AbstractVarInfo = VarInfo(),
     sampler::AbstractSampler = SampleFromPrior(),
-    context::AbstractContext = DefaultContext()
+    context::AbstractContext = DefaultContext(),
 )
     if Threads.nthreads() == 1
         return evaluate_threadunsafe(rng, model, varinfo, sampler, context)
     else
         return evaluate_threadsafe(rng, model, varinfo, sampler, context)
     end
 end
+function (model::Model)(args...)
+    return model(Random.GLOBAL_RNG, args...)
+end
+
+# without VarInfo
+function (model::Model)(
+    rng::Random.AbstractRNG,
+    sampler::AbstractSampler,
+    args...,
+)
+    return model(rng, VarInfo(), sampler, args...)
+end
+
+# without VarInfo and without AbstractSampler
+function (model::Model)(rng::Random.AbstractRNG, context::AbstractContext)
+    return model(rng, VarInfo(), SampleFromPrior(), context)
+end
 
 """
     evaluate_threadunsafe(rng, model, varinfo, sampler, context)

test/model.jl

@@ -45,6 +45,16 @@ Random.seed!(1234)
         end
     end
 
+    @testset "defaults without VarInfo, Sampler, and Context" begin
+        model = gdemo_default
+
+        Random.seed!(100)
+        s, m = model()
+
+        Random.seed!(100)
+        @test model(Random.GLOBAL_RNG) == (s, m)
+    end
+
     @testset "setval! & generated_quantities" begin
         @model function demo1(xs, ::Type{TV} = Vector{Float64}) where {TV}
             m = TV(undef, 2)