Add hljs class to all code blocks

This adds hljs to all code blocks for two reasons:

 - nohighlight blocks are left untouched by HighlightJS, meaning that
   the hljs class isn't attached at runtime to those blocks. Adding this
   explicitly makes sure that CSS rules for code blocks still apply
   such that the correct "regular text color" is used.
 - If JavaScript is disabled in the browser this makes sure that at
   least the intended "regular text color" is used for code blocks.

CHANGELOG.md

@@ -21,6 +21,8 @@
 
 * ![Enhancement][badge-enhancement] The `julia>` prompt is now colored in green in the `julia-repl` language highlighting. ([#1639][github-1639], [#1641][github-1641])
 
+* ![Enhancement][badge-enhancement] The `.hljs` CSS class is now added to all code blocks to make sure that the correct text color is used for non-highlighted code blocks and if JavaScript is disabled. ([#1645][github-1645])
+
 * ![Enhancement][badge-enhancement] The sandbox module used for evaluating `@repl` and `@example` blocks is now removed (replaced with `Main`) in text output. ([#1633][github-1633])
 
 * ![Enhancement][badge-enhancement] `@repl`, `@example`, and `@eval` blocks now have `LineNumberNodes` inserted such that e.g. `@__FILE__` and `@__LINE__` give better output and not just `"none"` for the file and `1` for the line. This requires Julia 1.6 or higher (no change on earlier Julia versions). ([#1634][github-1634])
@@ -879,6 +881,7 @@
 [github-1634]: https://github.com/JuliaDocs/Documenter.jl/pull/1634
 [github-1639]: https://github.com/JuliaDocs/Documenter.jl/issues/1639
 [github-1641]: https://github.com/JuliaDocs/Documenter.jl/pull/1641
+[github-1645]: https://github.com/JuliaDocs/Documenter.jl/pull/1645
 
 [julia-38079]: https://github.com/JuliaLang/julia/issues/38079
 [julia-39841]: https://github.com/JuliaLang/julia/pull/39841

src/Writers/HTMLWriter.jl

@@ -1762,15 +1762,15 @@ mdconvert(b::Markdown.Bold, parent; kwargs...) = Tag(:strong)(mdconvert(b.text,
 function mdconvert(c::Markdown.Code, parent::MDBlockContext; settings::Union{HTML,Nothing}=nothing, kwargs...)
     @tags pre code
     language = Utilities.codelang(c.language)
-    class = isempty(language) ? "nohighlight" : "language-$(language)"
     if language == "documenter-ansi" # From @repl blocks (through MultiCodeBlock)
-        return pre(domify_ansicoloredtext(c.code, "nohighlight"))
+        return pre(domify_ansicoloredtext(c.code, "nohighlight hljs"))
     elseif settings !== nothing && settings.prerender &&
            !(isempty(language) || language == "nohighlight")
         r = hljs_prerender(c, settings)
         r !== nothing && return r
     end
-    return pre(code[".$class"](c.code))
+    class = isempty(language) ? "nohighlight" : "language-$(language)"
+    return pre(code[".$(class) .hljs"](c.code))
 end
 function mdconvert(mcb::Documents.MultiCodeBlock, parent::MDBlockContext; kwargs...)
     @tags pre br
@@ -2005,7 +2005,7 @@ function mdconvert(d::Dict{MIME,Any}, parent; kwargs...)
     elseif haskey(d, MIME"text/plain"())
         @tags pre
         text = d[MIME"text/plain"()]
-        return pre[".documenter-example-output"](domify_ansicoloredtext(text, "nohighlight"))
+        return pre[".documenter-example-output"](domify_ansicoloredtext(text, "nohighlight hljs"))
     else
         error("this should never happen.")
     end

test/prerender/prerender.jl

@@ -27,9 +27,9 @@ assets = read_assets()
 @test occursin("'highlight-llvm'", assets)
 @test occursin("/languages/llvm.min", assets)
 index = read_index()
-@test occursin("<code class=\"language-julia\">function f()", index)
-@test occursin("<code class=\"language-julia-repl\">julia&gt; function f()", index)
-@test occursin("<code class=\"language-llvm\">;  @ int.jl:87 within", index)
+@test occursin("<code class=\"language-julia hljs\">function f()", index)
+@test occursin("<code class=\"language-julia-repl hljs\">julia&gt; function f()", index)
+@test occursin("<code class=\"language-llvm hljs\">;  @ int.jl:87 within", index)
 
 # With prerender
 HLJSFILES = Documenter.Writers.HTMLWriter.HLJSFILES
@@ -51,9 +51,9 @@ for _ in 1:2 # test with and without highlightjs file given
     @test !occursin("'highlight-llvm'", assets)
     @test !occursin("/languages/llvm.min", assets)
     local index = read_index()
-    @test !occursin("<code class=\"language-julia\">function f()", index)
-    @test !occursin("<code class=\"language-julia-repl\">julia&gt; function f()", index)
-    @test !occursin("<code class=\"language-llvm\">;  @ int.jl:87 within", index)
+    @test !occursin("<code class=\"language-julia hljs\">function f()", index)
+    @test !occursin("<code class=\"language-julia-repl hljs\">julia&gt; function f()", index)
+    @test !occursin("<code class=\"language-llvm hljs\">;  @ int.jl:87 within", index)
     @test occursin("<code class=\"language-julia hljs\"><span class=\"hljs-keyword\">function</span> f()", index)
     @test occursin("<code class=\"language-julia-repl hljs\"><span class=\"hljs-meta\">julia&gt;</span>", index)
     @test occursin("<code class=\"language-llvm hljs\"><span class=\"hljs-comment\">;  @ int.jl:87", index)
@@ -78,9 +78,9 @@ assets = read_assets()
 @test !occursin("'highlight-llvm'", assets)
 @test !occursin("/languages/llvm.min", assets)
 index = read_index()
-@test !occursin("<code class=\"language-julia\">function f()", index)
-@test !occursin("<code class=\"language-julia-repl\">julia&gt; function f()", index)
-@test occursin("<code class=\"language-llvm\">;  @ int.jl:87 within", index)
+@test !occursin("<code class=\"language-julia hljs\">function f()", index)
+@test !occursin("<code class=\"language-julia-repl hljs\">julia&gt; function f()", index)
+@test occursin("<code class=\"language-llvm hljs\">;  @ int.jl:87 within", index)
 @test occursin("<code class=\"language-julia hljs\"><span class=\"hljs-keyword\">function</span> f()", index)
 @test occursin("<code class=\"language-julia-repl hljs\"><span class=\"hljs-meta\">julia&gt;</span>", index)
 @test !occursin("<code class=\"language-llvm hljs\"><span class=\"hljs-comment\">;  @ int.jl:87", index)