fn parse_globs()

in src/rust/engine/fs/src/lib.rs [328:404]
64 lines of code
8 McCabe index (conditional complexity)

  fn parse_globs(
    canonical_dir: Dir,
    symbolic_path: PathBuf,
    parts: &[Pattern],
  ) -> Result<Vec<PathGlob>, String> {
    if parts.is_empty() {
      Ok(vec![])
    } else if *DOUBLE_STAR == parts[0].as_str() {
      if parts.len() == 1 {
        // Per https://git-scm.com/docs/gitignore:
        //  "A trailing '/**' matches everything inside. For example, 'abc/**' matches all files
        //  inside directory "abc", relative to the location of the .gitignore file, with infinite
        //  depth."
        return Ok(vec![
          PathGlob::dir_wildcard(
            canonical_dir.clone(),
            symbolic_path.clone(),
            SINGLE_STAR_GLOB.clone(),
            vec![DOUBLE_STAR_GLOB.clone()],
          ),
          PathGlob::wildcard(canonical_dir, symbolic_path, SINGLE_STAR_GLOB.clone()),
        ]);
      }

      // There is a double-wildcard in a dirname of the path: double wildcards are recursive,
      // so there are two remainder possibilities: one with the double wildcard included, and the
      // other without.
      let pathglob_with_doublestar = PathGlob::dir_wildcard(
        canonical_dir.clone(),
        symbolic_path.clone(),
        SINGLE_STAR_GLOB.clone(),
        parts[0..].to_vec(),
      );
      let pathglob_no_doublestar = if parts.len() == 2 {
        PathGlob::wildcard(canonical_dir, symbolic_path, parts[1].clone())
      } else {
        PathGlob::dir_wildcard(
          canonical_dir,
          symbolic_path,
          parts[1].clone(),
          parts[2..].to_vec(),
        )
      };
      Ok(vec![pathglob_with_doublestar, pathglob_no_doublestar])
    } else if *PARENT_DIR == parts[0].as_str() {
      // A request for the parent of `canonical_dir`: since we've already expanded the directory
      // to make it canonical, we can safely drop it directly and recurse without this component.
      // The resulting symbolic path will continue to contain a literal `..`.
      let mut canonical_dir_parent = canonical_dir;
      let mut symbolic_path_parent = symbolic_path;
      if !canonical_dir_parent.0.pop() {
        let mut symbolic_path = symbolic_path_parent;
        symbolic_path.extend(parts.iter().map(Pattern::as_str));
        return Err(format!(
          "Globs may not traverse outside of the buildroot: {:?}",
          symbolic_path,
        ));
      }
      symbolic_path_parent.push(Path::new(*PARENT_DIR));
      PathGlob::parse_globs(canonical_dir_parent, symbolic_path_parent, &parts[1..])
    } else if parts.len() == 1 {
      // This is the path basename.
      Ok(vec![PathGlob::wildcard(
        canonical_dir,
        symbolic_path,
        parts[0].clone(),
      )])
    } else {
      // This is a path dirname.
      Ok(vec![PathGlob::dir_wildcard(
        canonical_dir,
        symbolic_path,
        parts[0].clone(),
        parts[1..].to_vec(),
      )])
    }
  }