Use BlueStyle and JuliaFormatter (#246)

We have been using JuliaFormatter quite successfully for some while in the JuliaGaussianProcesses organization, and I think it would be good to adopt some style guide also in DynamicPPL and other TuringLang packages. This helps to keep the code base consistent and, in my opinion, increases readability and reduces mental overhead.

I just chose [BlueStyle](https://github.com/invenia/BlueStyle) here since it is used in JuliaGaussianProcesses. I would be fine with YAS as well, I think a main criterion should just be that is supported by [JuliaFormatter](https://github.com/domluna/JuliaFormatter.jl) since this makes it much easier to format code correctly.

Speaking about convenience, I also added a configuration for JuliaFormatter such that one can just run `format(path_to_repo)` to re-format the codebase correctly (actually, that's what I did when putting together the PR). Moreover, I added a Github action that will automatically check and report if PRs are formatted correctly. It will even post suggestions with format fixes (if required) which is even more convenient.

.JuliaFormatter.toml

@@ -0,0 +1 @@
+style="blue"

.github/workflows/Format.yml

@@ -0,0 +1,33 @@
+name: Format
+
+on:
+  push:
+    branches:
+      # This is where pull requests from "bors r+" are built.
+      - staging
+      # This is where pull requests from "bors try" are built.
+      - trying
+      # Build the master branch.
+      - master
+  pull_request:
+
+jobs:
+  format:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: julia-actions/setup-julia@latest
+        with:
+          version: 1
+      - name: Format code
+        run: |
+          using Pkg
+          Pkg.add(; name="JuliaFormatter", uuid="98e50ef6-434e-11e9-1051-2b60c6c9e899")
+          using JuliaFormatter
+          format("."; verbose=true)
+        shell: julia --color=yes {0}
+      - uses: reviewdog/action-suggester@v1
+        if: github.event_name == 'pull_request'
+        with:
+          tool_name: JuliaFormatter
+          fail_on_error: true

README.md

@@ -5,6 +5,7 @@
 [![IntegrationTest](https://github.com/TuringLang/DynamicPPL.jl/workflows/IntegrationTest/badge.svg?branch=master)](https://github.com/TuringLang/DynamicPPL.jl/actions?query=workflow%3AIntegrationTest+branch%3Amaster)
 [![Coverage Status](https://coveralls.io/repos/github/TuringLang/DynamicPPL.jl/badge.svg?branch=master)](https://coveralls.io/github/TuringLang/DynamicPPL.jl?branch=master)
 [![Codecov](https://codecov.io/gh/TuringLang/DynamicPPL.jl/branch/master/graph/badge.svg)](https://codecov.io/gh/TuringLang/DynamicPPL.jl)
+[![Code Style: Blue](https://img.shields.io/badge/code%20style-blue-4495d1.svg)](https://github.com/invenia/BlueStyle)
 [![ColPrac: Contributor's Guide on Collaborative Practices for Community Packages](https://img.shields.io/badge/ColPrac-Contributor's%20Guide-blueviolet)](https://colprac.sciml.ai/)
 [![Bors enabled](https://bors.tech/images/badge_small.svg)](https://app.bors.tech/repositories/24589)
 

bors.toml

@@ -15,7 +15,8 @@ status = [
   "test (1.%, windows-latest, x64, 2)",
   "test (1, windows-latest, x64, 1)",
   "test (1, windows-latest, x64, 2)",
-  "Turing.jl"
+  "Turing.jl",
+  "format"
 ]
 delete_merged_branches = true
 # Require at least on approval of a project member.

src/DynamicPPL.jl

@@ -5,101 +5,101 @@ using AbstractPPL
 using Distributions
 using Bijectors
 
-import AbstractMCMC
-import ChainRulesCore
-import NaturalSort
-import MacroTools
-import ZygoteRules
+using AbstractMCMC: AbstractMCMC
+using ChainRulesCore: ChainRulesCore
+using NaturalSort: NaturalSort
+using MacroTools: MacroTools
+using ZygoteRules: ZygoteRules
 
-import Random
+using Random: Random
 
-import Base: Symbol,
-             ==,
-             hash,
-             getindex,
-             setindex!,
-             push!,
-             show,
-             isempty,
-             empty!,
-             getproperty,
-             setproperty!,
-             keys,
-             haskey
+import Base:
+    Symbol,
+    ==,
+    hash,
+    getindex,
+    setindex!,
+    push!,
+    show,
+    isempty,
+    empty!,
+    getproperty,
+    setproperty!,
+    keys,
+    haskey
 
 # VarInfo
-export  AbstractVarInfo,
-        VarInfo,
-        UntypedVarInfo,
-        TypedVarInfo,
-        getlogp,
-        setlogp!,
-        acclogp!,
-        resetlogp!,
-        get_num_produce,
-        set_num_produce!,
-        reset_num_produce!,
-        increment_num_produce!,
-        set_retained_vns_del_by_spl!,
-        is_flagged,
-        set_flag!,
-        unset_flag!,
-        setgid!,
-        updategid!,
-        setorder!,
-        istrans,
-        link!,
-        invlink!,
-        tonamedtuple,
-# VarName (reexport from AbstractPPL)
-        VarName,
-        inspace,
-        subsumes,
-        @varname,
-# Compiler
-        @model,
-# Utilities
-        vectorize,
-        reconstruct,
-        reconstruct!,
-        Sample,
-        init,
-        vectorize,
-# Model
-        Model,
-        getmissings,
-        getargnames,
-        generated_quantities,
-# Samplers
-        Sampler,
-        SampleFromPrior,
-        SampleFromUniform,
-# Contexts
-        DefaultContext,
-        LikelihoodContext,
-        PriorContext,
-        MiniBatchContext,
-        PrefixContext,
-        assume,
-        dot_assume,
-        observer,
-        dot_observe,
-        tilde,
-        dot_tilde,
-# Pseudo distributions
-        NamedDist,
-        NoDist,
-# Prob macros
-        @prob_str,
-        @logprob_str,
-# Convenience functions
-        logprior,
-        logjoint,
-        pointwise_loglikelihoods,
-# Convenience macros
-        @addlogprob!,
-        @submodel
-
+export AbstractVarInfo,
+    VarInfo,
+    UntypedVarInfo,
+    TypedVarInfo,
+    getlogp,
+    setlogp!,
+    acclogp!,
+    resetlogp!,
+    get_num_produce,
+    set_num_produce!,
+    reset_num_produce!,
+    increment_num_produce!,
+    set_retained_vns_del_by_spl!,
+    is_flagged,
+    set_flag!,
+    unset_flag!,
+    setgid!,
+    updategid!,
+    setorder!,
+    istrans,
+    link!,
+    invlink!,
+    tonamedtuple,
+    # VarName (reexport from AbstractPPL)
+    VarName,
+    inspace,
+    subsumes,
+    @varname,
+    # Compiler
+    @model,
+    # Utilities
+    vectorize,
+    reconstruct,
+    reconstruct!,
+    Sample,
+    init,
+    vectorize,
+    # Model
+    Model,
+    getmissings,
+    getargnames,
+    generated_quantities,
+    # Samplers
+    Sampler,
+    SampleFromPrior,
+    SampleFromUniform,
+    # Contexts
+    DefaultContext,
+    LikelihoodContext,
+    PriorContext,
+    MiniBatchContext,
+    PrefixContext,
+    assume,
+    dot_assume,
+    observer,
+    dot_observe,
+    tilde,
+    dot_tilde,
+    # Pseudo distributions
+    NamedDist,
+    NoDist,
+    # Prob macros
+    @prob_str,
+    @logprob_str,
+    # Convenience functions
+    logprior,
+    logjoint,
+    pointwise_loglikelihoods,
+    # Convenience macros
+    @addlogprob!,
+    @submodel
 
 # Reexport
 using Distributions: loglikelihood
@@ -112,7 +112,6 @@ function getspace end
 abstract type AbstractVarInfo <: AbstractModelTrace end
 abstract type AbstractContext end
 
-
 include("utils.jl")
 include("selector.jl")
 include("model.jl")

src/compat/ad.jl

@@ -1,21 +1,15 @@
 # See https://github.com/TuringLang/Turing.jl/issues/1199
 ChainRulesCore.@non_differentiable push!(
-    vi::VarInfo,
-    vn::VarName,
-    r,
-    dist::Distribution,
-    gidset::Set{Selector}
+    vi::VarInfo, vn::VarName, r, dist::Distribution, gidset::Set{Selector}
 )
 
 ChainRulesCore.@non_differentiable updategid!(
-    vi::AbstractVarInfo,
-    vn::VarName,
-    spl::Sampler,
+    vi::AbstractVarInfo, vn::VarName, spl::Sampler
 )
 
 # https://github.com/TuringLang/Turing.jl/issues/1595
 ZygoteRules.@adjoint function dot_observe(
-    spl::Union{SampleFromPrior, SampleFromUniform},
+    spl::Union{SampleFromPrior,SampleFromUniform},
     dists::AbstractArray{<:Distribution},
     value::AbstractArray,
     vi,