77 lines
2 KiB
Ruby
77 lines
2 KiB
Ruby
# frozen_string_literal: true
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require 'rouge/plugins/common_mark'
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require 'rouge/plugins/redcarpet'
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module Banzai
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module Filter
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# HTML Filter to highlight fenced code blocks
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#
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class SyntaxHighlightFilter < HTML::Pipeline::Filter
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def call
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doc.search('pre > code').each do |node|
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highlight_node(node)
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end
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doc
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end
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def highlight_node(node)
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css_classes = +'code highlight js-syntax-highlight'
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lang = node.attr('lang')
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retried = false
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if use_rouge?(lang)
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lexer = lexer_for(lang)
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language = lexer.tag
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else
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lexer = Rouge::Lexers::PlainText.new
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language = lang
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end
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begin
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code = Rouge::Formatters::HTMLGitlab.format(lex(lexer, node.text), tag: language)
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css_classes << " #{language}" if language
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rescue
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# Gracefully handle syntax highlighter bugs/errors to ensure users can
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# still access an issue/comment/etc. First, retry with the plain text
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# filter. If that fails, then just skip this entirely, but that would
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# be a pretty bad upstream bug.
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return if retried
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language = nil
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lexer = Rouge::Lexers::PlainText.new
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retried = true
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retry
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end
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highlighted = %(<pre class="#{css_classes}" lang="#{language}" v-pre="true"><code>#{code}</code></pre>)
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# Extracted to a method to measure it
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replace_parent_pre_element(node, highlighted)
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end
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private
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# Separate method so it can be instrumented.
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def lex(lexer, code)
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lexer.lex(code)
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end
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def lexer_for(language)
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(Rouge::Lexer.find(language) || Rouge::Lexers::PlainText).new
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end
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def replace_parent_pre_element(node, highlighted)
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# Replace the parent `pre` element with the entire highlighted block
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node.parent.replace(highlighted)
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end
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def use_rouge?(language)
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%w(math mermaid plantuml).exclude?(language)
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end
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end
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end
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end
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