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111 lines
3.0 KiB
111 lines
3.0 KiB
# Copyright 2014 Donald Stufft
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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from __future__ import absolute_import, division, print_function
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import re
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import warnings
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import pygments
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import pygments.lexers
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import pygments.formatters
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from six.moves import html_parser
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from .clean import clean
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_EXTRA_WARNING = (
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"Markdown renderers are not available. "
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"Install 'readme_render[md]' to enable Markdown rendering."
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)
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try:
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import cmarkgfm
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variants = {
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"GFM": cmarkgfm.github_flavored_markdown_to_html,
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"CommonMark": cmarkgfm.markdown_to_html,
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}
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except ImportError:
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warnings.warn(_EXTRA_WARNING)
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variants = {}
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# Make code fences with `python` as the language default to highlighting as
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# Python 3.
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_LANG_ALIASES = {
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'python': 'python3',
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}
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def render(raw, variant="GFM", **kwargs):
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if not variants:
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warnings.warn(_EXTRA_WARNING)
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return None
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renderer = variants.get(variant)
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if not renderer:
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return None
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rendered = renderer(raw)
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if not rendered:
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return None
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highlighted = _highlight(rendered)
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cleaned = clean(highlighted)
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return cleaned
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def _highlight(html):
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"""Syntax-highlights HTML-rendered Markdown.
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Plucks sections to highlight that conform the the GitHub fenced code info
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string as defined at https://github.github.com/gfm/#info-string.
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Args:
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html (str): The rendered HTML.
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Returns:
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str: The HTML with Pygments syntax highlighting applied to all code
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blocks.
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"""
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formatter = pygments.formatters.HtmlFormatter(nowrap=True)
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code_expr = re.compile(
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r'<pre><code class="language-(?P<lang>.+?)">(?P<code>.+?)'
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r'</code></pre>', re.DOTALL)
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def replacer(match):
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try:
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lang = match.group('lang')
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lang = _LANG_ALIASES.get(lang, lang)
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lexer = pygments.lexers.get_lexer_by_name(lang)
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except ValueError:
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lexer = pygments.lexers.TextLexer()
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code = match.group('code')
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# Decode html entities in the code. cmark tries to be helpful and
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# translate '"' to '"', but it confuses pygments. Pygments will
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# escape any html entities when re-writing the code, and we run
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# everything through bleach after.
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code = html_parser.HTMLParser().unescape(code)
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highlighted = pygments.highlight(code, lexer, formatter)
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return '<pre>{}</pre>'.format(highlighted)
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result = code_expr.sub(replacer, html)
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return result
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