Fix conditioned doctest for Julia 1.8-beta1 (#388)

The tests were failing on a changed display for var objects:

```
│ Subexpression:
│ 
│ conditioned(cm)
│ 
│ Evaluated output:
│ 
│ (x = 100.0, var"a.m" = 1.0)
│ 
│ Expected output:
│ 
│ (x = 100.0, a.m = 1.0)
│ 
│   diff =
│    Warning: Diff output requires color.
│    (x = 100.0, a.m var"a.m" = 1.0)
```

This is why the the nanosoldier runs show that DynamicPPL fails on Julia 1.8-beta1 (https://s3.amazonaws.com/julialang-reports/nanosoldier/pkgeval/by_hash/fb69baf_vs_40279f9/report.html).

I've tried to come up with a doctestfilter, but don't think that's possible in this case. Therefore, I suggest that we only run the tests on the latest stable release. This solves two problems:

- Nightly/beta/release-candidate releases failing due to changes in how output appears
- Simplify code; especially avoids that a doctestfilter allows some test to pass where it should fail

I've tested this PR on Julia 1.8.0-beta1 locally. All tests passed.

Co-authored-by: Rik Huijzer <[email protected]>

Author: rikhuijzer

Project.toml

@@ -1,6 +1,6 @@
 name = "DynamicPPL"
 uuid = "366bfd00-2699-11ea-058f-f148b4cae6d8"
-version = "0.17.8"
+version = "0.17.9"
 
 [deps]
 AbstractMCMC = "80f14c24-f653-4e6a-9b94-39d6b0f70001"

docs/make.jl

@@ -11,17 +11,6 @@ makedocs(;
     pages=["Home" => "index.md", "TestUtils" => "test_utils.md"],
     strict=true,
     checkdocs=:exports,
-    doctestfilters=[
-        # Older versions will show "0 element Array" instead of "Type[]".
-        r"(Any\[\]|0-element Array{.+,[0-9]+})",
-        # Older versions will show "Array{...,1}" instead of "Vector{...}".
-        r"(Array{.+,\s?1}|Vector{.+})",
-        # Older versions will show "Array{...,2}" instead of "Matrix{...}".
-        r"(Array{.+,\s?2}|Matrix{.+})",
-        # Errors from macros sometimes result in `LoadError: LoadError:`
-        # rather than `LoadError:`, depending on Julia version.
-        r"ERROR: (LoadError:\s)+",
-    ],
 )
 
 deploydocs(; repo="github.com/TuringLang/DynamicPPL.jl.git", push_preview=true)

src/model.jl

@@ -242,11 +242,11 @@ in their trace/`VarInfo`:
 
 ```jldoctest condition
 julia> keys(VarInfo(demo_outer()))
-1-element Vector{VarName{:m, Tuple{}}}:
+1-element Vector{VarName{:m, Setfield.IdentityLens}}:
  m
 
 julia> keys(VarInfo(demo_outer_prefix()))
-1-element Vector{VarName{Symbol("inner.m"), Tuple{}}}:
+1-element Vector{VarName{Symbol("inner.m"), Setfield.IdentityLens}}:
  inner.m
 ```
 
@@ -350,14 +350,17 @@ julia> conditioned(cm)
 julia> # Since we conditioned on `m`, not `a.m` as it will appear after prefixed,
        # `a.m` is treated as a random variable.
        keys(VarInfo(cm))
-1-element Vector{VarName{Symbol("a.m"), Tuple{}}}:
+1-element Vector{VarName{Symbol("a.m"), Setfield.IdentityLens}}:
  a.m
 
 julia> # If we instead condition on `a.m`, `m` in the model will be considered an observation.
        cm = condition(contextualize(m, PrefixContext{:a}(condition(var"a.m"=1.0))), x=100.0);
 
-julia> conditioned(cm)
-(x = 100.0, a.m = 1.0)
+julia> conditioned(cm).x
+100.0
+
+julia> conditioned(cm).var"a.m"
+1.0
 
 julia> keys(VarInfo(cm)) # <= no variables are sampled
 Any[]