From 377643f9848cf88b79e7b24d1fce852eccec5e43 Mon Sep 17 00:00:00 2001
From: Jakob Peters <jakobj.peters@gmail.com>
Date: Sun, 24 Nov 2024 08:27:25 -0800
Subject: [PATCH] Highlight circular references (#56663)

The text `"#= circular reference @-$d =#"` is printed yellow. Adds a test with the context `:color => true`.
---
 base/show.jl | 2 +-
 test/show.jl | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/base/show.jl b/base/show.jl
index e6c2367e438b3..23957d6e29b2d 100644
--- a/base/show.jl
+++ b/base/show.jl
@@ -443,7 +443,7 @@ function show_circular(io::IOContext, @nospecialize(x))
     for (k, v) in io.dict
         if k === :SHOWN_SET
             if v === x
-                print(io, "#= circular reference @-$d =#")
+                printstyled(io, "#= circular reference @-$d =#"; color = :yellow)
                 return true
             end
             d += 1
diff --git a/test/show.jl b/test/show.jl
index de5cf32b726ee..07916c249d533 100644
--- a/test/show.jl
+++ b/test/show.jl
@@ -1275,6 +1275,7 @@ let x = [], y = [], z = Base.ImmutableDict(x => y)
     push!(y, x)
     push!(y, z)
     @test replstr(x) == "1-element Vector{Any}:\n Any[Any[#= circular reference @-2 =#], Base.ImmutableDict{Vector{Any}, Vector{Any}}([#= circular reference @-3 =#] => [#= circular reference @-2 =#])]"
+    @test replstr(x, :color => true) == "1-element Vector{Any}:\n Any[Any[\e[33m#= circular reference @-2 =#\e[39m], Base.ImmutableDict{Vector{Any}, Vector{Any}}([\e[33m#= circular reference @-3 =#\e[39m] => [\e[33m#= circular reference @-2 =#\e[39m])]"
     @test repr(z) == "Base.ImmutableDict{Vector{Any}, Vector{Any}}([Any[Any[#= circular reference @-2 =#], Base.ImmutableDict{Vector{Any}, Vector{Any}}(#= circular reference @-3 =#)]] => [Any[Any[#= circular reference @-2 =#]], Base.ImmutableDict{Vector{Any}, Vector{Any}}(#= circular reference @-2 =#)])"
     @test sprint(dump, x) == """
         Array{Any}((1,))