From c84c7ffe6d2b5e538f89b18d58dfdf4d7f3f0318 Mon Sep 17 00:00:00 2001
From: t-bltg <tf.bltg@gmail.com>
Date: Tue, 29 Nov 2022 13:56:42 +0100
Subject: [PATCH] enhance diagnostics

---
 src/Plots.jl          |  2 +-
 src/backends.jl       | 21 +++++++++++++++++---
 test/test_axes.jl     |  2 +-
 test/test_backends.jl | 46 +++++++++++++++++++++----------------------
 4 files changed, 43 insertions(+), 28 deletions(-)

diff --git a/src/Plots.jl b/src/Plots.jl
index 089861de85..4719ff81e3 100644
--- a/src/Plots.jl
+++ b/src/Plots.jl
@@ -18,7 +18,7 @@ function _check_compat(sim::Module)
     haskey(_plots_compats, sim_str) || return nothing
     be_v = Pkg.Types.read_project(joinpath(Base.pkgdir(sim), "Project.toml")).version
     be_c = _plots_compats[sim_str]
-    if be_c isa String # julia 1.6
+    if be_c isa String  # julia 1.6
         if !(be_v in Pkg.Types.semver_spec(be_c))
             @warn "$sim $be_v is not compatible with this version of Plots. The declared compatibility is $(be_c)."
         end
diff --git a/src/backends.jl b/src/backends.jl
index 6379281f85..21340e6eab 100644
--- a/src/backends.jl
+++ b/src/backends.jl
@@ -144,9 +144,24 @@ set_backend!(; kw...) = set_preferences!(Plots, "backend" => nothing; kw...)
 set_backend!(backend::Union{AbstractString,Symbol}; kw...) =
     set_preferences!(Plots, "backend" => lowercase(string(backend)); kw...)
 
-function diagnostics()
-    from = haskey(ENV, "PLOTS_DEFAULT_BACKEND") ? "environment variable" : "`Preferences`"
-    @info "selected `Plots` backend: $(backend()), from $from" _current_plots_version
+function diagnostics(io::IO=stdout)
+    from = if has_preference(Plots, "backend")
+        "`Preferences`"
+    elseif haskey(ENV, "PLOTS_DEFAULT_BACKEND")
+        "environment variable"
+    else
+        "fallback"
+    end
+    if (be = backend_name()) !== :none
+        be_name = string(backend_package_name(be))
+        @info "selected `Plots` backend: $be_name, from $from"
+        Pkg.status(
+            ["Plots", "RecipesBase", "RecipesPipeline", be_name];
+            mode = Pkg.PKGMODE_MANIFEST, io
+        )
+    else
+        @info "no `Plots` backends currently initialized"
+    end
     nothing
 end
 
diff --git a/test/test_axes.jl b/test/test_axes.jl
index 543516e7a3..7a1eb0d95c 100644
--- a/test/test_axes.jl
+++ b/test/test_axes.jl
@@ -244,7 +244,7 @@ end
             else
                 length(minor_ticks)
             end
-            display(pl)
+            show(devnull, pl)
             @test n_minor_ticks == n_expected_minor_ticks
         end
     end
diff --git a/test/test_backends.jl b/test/test_backends.jl
index 183bab1e24..a54e231d59 100644
--- a/test/test_backends.jl
+++ b/test/test_backends.jl
@@ -128,32 +128,38 @@ end
 
     Plots.set_backend!(:gaston; force = true)
     @test Plots.load_default_backend() == Plots.GastonBackend()
+    @test_logs (:info, r".*Preferences") Plots.diagnostics(devnull)
     proc = ```
     $(Base.julia_cmd()) -e "
-        ENV[\"PLOTS_PRECOMPILE\"] = false
-        using Pkg
-        Pkg.activate(; temp = true)
-        Pkg.develop(; path = \"$(escape_string(pkgdir(Plots)))\")
+    using Pkg; io = devnull
+    Pkg.activate(; temp = true, io)
+    Pkg.develop(; path = \"$(escape_string(pkgdir(Plots)))\", io)
+    withenv(\"PLOTS_PRECOMPILE\" => false) do
         using Plots, Test
+        Plots.diagnostics(io)
         @test backend() == Plots.GastonBackend()
+    end
     "``` |> run
     @test success(proc)
-    Plots.set_backend!(; force = true)
+    Plots.set_backend!(; force = true)  # clear `Preferences` key
 
-    @test_logs (:warn, r".*is not a supported backend") withenv(
-        "PLOTS_DEFAULT_BACKEND" => "invalid",
-    ) do
-        Plots.load_default_backend()
+    withenv("PLOTS_DEFAULT_BACKEND" => "invalid") do
+        @test_logs (:warn, r".*is not a supported backend") Plots.load_default_backend()
     end
     @test_logs (:warn, r".*is not a supported backend") backend(:invalid)
 
     @test Plots.load_default_backend() == Plots.GRBackend()
 
-    @test withenv("PLOTS_DEFAULT_BACKEND" => "unicodeplots") do
-        Plots.load_default_backend()
-    end == Plots.UnicodePlotsBackend()
+    withenv("PLOTS_DEFAULT_BACKEND" => "unicodeplots") do
+        @test_logs (:info, r".*environment variable") Plots.diagnostics(devnull)
+        @test Plots.load_default_backend() == Plots.UnicodePlotsBackend()
+    end
 
     @test Plots.load_default_backend() == Plots.GRBackend()
+    @test Plots.backend_package_name() == :GR
+    @test Plots.backend_name() === :gr
+
+    @test_logs (:info, r".*fallback") Plots.diagnostics(devnull)
 end
 
 @testset "UnicodePlots" begin
@@ -210,17 +216,11 @@ end
         # NOTE: use `ENV["VISUAL_REGRESSION_TESTS_AUTO"] = true;` to automatically replace reference images
         @test backend() == Plots.GRBackend()
         @test backend_name() === :gr
-        withenv("PLOTS_TEST" => true, "GKSwstype" => "nul") do
-            @static if haskey(ENV, "APPVEYOR")
-                @info "Skipping GR image comparison tests on AppVeyor"
-            else
-                image_comparison_facts(
-                    :gr,
-                    tol = PLOTS_IMG_TOL,
-                    skip = vcat(Plots._backend_skips[:gr], blacklist),
-                )
-            end
-        end
+        image_comparison_facts(
+            :gr,
+            tol = PLOTS_IMG_TOL,
+            skip = vcat(Plots._backend_skips[:gr], blacklist),
+        )
     end
 end