Fix zero-length Markdown headers (#47725)

* Fix zero-length Markdown headers * Add test on empty header
JuliaLang · Dec 27, 2022 · a40e24e · a40e24e
1 parent 4c2a431
commit a40e24e
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diff --git a/stdlib/Markdown/src/render/terminal/render.jl b/stdlib/Markdown/src/render/terminal/render.jl
@@ -88,7 +88,8 @@ function _term_header(io::IO, md, char, columns)
  if line_no > 1
  line_width = max(line_width, div(columns, 3))
  end
- char != ' ' && print(io, '\n', ' '^(margin), char^(line_width-margin))
+ header_width = max(0, line_width-margin)
+ char != ' ' && header_width > 0 && print(io, '\n', ' '^(margin), char^header_width)
  end
 end
 

diff --git a/stdlib/Markdown/test/runtests.jl b/stdlib/Markdown/test/runtests.jl
@@ -377,6 +377,7 @@ table = md"""
 let out =
  @test sprint(show, "text/plain", book) ==
  " Title\n ≡≡≡≡≡\n\n Some discussion\n\n │ A quote\n\n Section important\n =================\n\n Some bolded\n\n • list1\n\n • list2"
+ @test sprint(show, "text/plain", md"#") == " " # edge case of empty header
  @test sprint(show, "text/markdown", book) ==
  """
  # Title