repo_description: Empowering everyone to build reliable and efficient software.
repo_topics: compiler language rust
code: //! Standalone markdown rendering.
  //!
  //! For the (much more common) case of rendering markdown in doc-comments, see
  //! [crate::html::markdown].
  //!
  //! This is used when [rendering a markdown file to an html file][docs], without processing
  //! rust source code.
  //!
  //! [docs]: https://doc.rust-lang.org/stable/rustdoc/#using-standalone-markdown-files
  
  use std::fmt::{self, Write as _};
  use std::fs::{File, create_dir_all};
  use std::io::prelude::*;
  use std::path::PathBuf;
  use std::sync::Arc;
  
  use rustc_span::SourceFile;
  use rustc_span::edition::Edition;
  
  use crate::config::RenderOptions;
  use crate::html::escape::Escape;
  use crate::html::markdown;
  use crate::html::markdown::{ErrorCodes, HeadingOffset, IdMap, Markdown, MarkdownWithToc};
  
  /// Separate any lines at the start of the file that begin with `# ` or `%`.
  fn extract_leading_metadata(s: &str) -> (Vec<&str>, &str) {
      let mut metadata = Vec::new();
      let mut count = 0;
  
      for line in s.lines() {
          if line.starts_with("# ") || line.starts_with('%') {
              // trim the whitespace after the symbol
              metadata.push(line[1..].trim_start());
              count += line.len() + 1;
          } else {
              return (metadata, &s[count..]);
          }
      }
  
      // if we're here, then all lines were metadata `# ` or `%` lines.
      (metadata, "")
  }
  
  /// Render `input` (e.g., "foo.md") into an HTML file in `output`
  /// (e.g., output = "bar" => "bar/foo.html").
  ///
  /// Requires session globals to be available, for symbol interning.
  pub(crate) fn render_and_write(
      input: Arc<SourceFile>,
      options: RenderOptions,
      edition: Edition,
  ) -> Result<(), String> {
      if let Err(e) = create_dir_all(&options.output) {
          return Err(format!("{output}: {e}", output = options.output.display()));
      }
  
      let input_path = input.name.clone().into_local_path().unwrap_or(PathBuf::new());
      let mut output = options.output;
      output.push(input_path.file_name().unwrap());
      output.set_extension("html");
  
      let mut css = String::new();
      for name in &options.markdown_css {
          write!(css, r#"<link rel="stylesheet" href="{name}">"#)
              .expect("Writing to a String can't fail");
      }
  
      let input_str = input.src.as_ref().map(|src| &src[..]).unwrap_or("");
      let playground_url = options.markdown_playground_url.or(options.playground_url);
      let playground = playground_url.map(|url| markdown::Playground { crate_name: None, url });
  
      let mut out =
          File::create(&output).map_err(|e| format!("{output}: {e}", output = output.display()))?;
  
      let (metadata, text) = extract_leading_metadata(&input_str);
      if metadata.is_empty() {
          return Err("invalid markdown file: no initial lines starting with `# ` or `%`".to_owned());
      }
      let title = metadata[0];
  
      let error_codes = ErrorCodes::from(options.unstable_features.is_nightly_build());
      let text = fmt::from_fn(|f| {
          if !options.markdown_no_toc {
              MarkdownWithToc {
                  content: text,
                  links: &[],
                  ids: &mut IdMap::new(),
                  error_codes,
                  edition,
                  playground: &playground,
              }
              .write_into(f)
          } else {
              Markdown {
                  content: text,
                  links: &[],
                  ids: &mut IdMap::new(),
                  error_codes,
                  edition,
                  playground: &playground,
                  heading_offset: HeadingOffset::H1,
              }
              .write_into(f)
          }
      });
  
      let res = write!(
          &mut out,
          r#"<!DOCTYPE html>
  <html lang="en">
  <head>
      <meta charset="utf-8">
      <meta name="viewport" content="width=device-width, initial-scale=1.0">
      <meta name="generator" content="rustdoc">
      <title>{title}</title>
  
      {css}
      {in_header}
  </head>
  <body class="rustdoc">
      <!--[if lte IE 8]>
      <div class="warning">
          This old browser is unsupported and will most likely display funky
          things.
      </div>
      <![endif]-->
  
      {before_content}
      <h1 class="title">{title}</h1>
      {text}
      {after_content}
  </body>
  </html>"#,
          title = Escape(title),
          in_header = options.external_html.in_header,
          before_content = options.external_html.before_content,
          after_content = options.external_html.after_content,
      );
  
      res.map_err(|e| format!("cannot write to `{output}`: {e}", output = output.display()))
  }
  