Many warnings for the same missing scanner in the same session

[Phrogz]

I am converting many small Markdown snippets using kramdown+CodeRay.

def convert(markdown)
  Kramdown::Document.new(markdown, coderay_line_numbers:nil, coderay_css: :class).to_html
end

Each time there is a code block tagged with the Lua language I get:

CodeRay::Scanners could not load plugin :lua; falling back to :text

As a result my automated script for generating documentation is spitting out ~100 lines on stderr where one would suffice.

It would be nice if this warning could only be emitted once per language per process. Would you accept a patch for this, e.g. storing an instance variable on CodeRay::PluginHost referencing a hash of languages that have been warned about?

[korny]

It would be nice if this warning could only be emitted once per language per process.

Good idea. Can you make a PR?

[Phrogz]

Will do. (Now that I've locally added support for Lua, this is a much lower priority for me, though. ;)

[Phrogz]

BTW, I tried to figure out how to make a test for this, but couldn't figure it out. I'll probably PR without one.

[korny]

There's an assert_warning helper somewhere.

[korny]

I just disabled the warning completely. If we define a :default in the _map.rb file, it expresses intent to have a fallback instead of an error: Scanners fall back to plain text, while Encoders will raise an error.