text: """
  Requirements file parsing
  """
  
  import optparse
  import os
  import re
  import shlex
  import urllib.parse
  from optparse import Values
  from typing import TYPE_CHECKING, Any, Callable, Dict, Iterator, List, Optional, Tuple
  
  from pipenv.patched.notpip._internal.cli import cmdoptions
  from pipenv.patched.notpip._internal.exceptions import InstallationError, RequirementsFileParseError
  from pipenv.patched.notpip._internal.models.search_scope import SearchScope
  from pipenv.patched.notpip._internal.network.session import PipSession
  from pipenv.patched.notpip._internal.network.utils import raise_for_status
  from pipenv.patched.notpip._internal.utils.encoding import auto_decode
  from pipenv.patched.notpip._internal.utils.urls import get_url_scheme
  
  if TYPE_CHECKING:
      # NoReturn introduced in 3.6.2; imported only for type checking to maintain
      # pip compatibility with older patch versions of Python 3.6
      from typing import NoReturn
  
      from pipenv.patched.notpip._internal.index.package_finder import PackageFinder
  
  __all__ = ['parse_requirements']
  
  ReqFileLines = Iterator[Tuple[int, str]]
  
  LineParser = Callable[[str], Tuple[str, Values]]
  
  SCHEME_RE = re.compile(r'^(http|https|file):', re.I)
  COMMENT_RE = re.compile(r'(^|\s+)#.*$')
  
  # Matches environment variable-style values in '${MY_VARIABLE_1}' with the
  # variable name consisting of only uppercase letters, digits or the '_'
  # (underscore). This follows the POSIX standard defined in IEEE Std 1003.1,
  # 2013 Edition.
  ENV_VAR_RE = re.compile(r'(?P<var>\$\{(?P<name>[A-Z0-9_]+)\})')
  
  SUPPORTED_OPTIONS: List[Callable[..., optparse.Option]] = [
      cmdoptions.index_url,
      cmdoptions.extra_index_url,
      cmdoptions.no_index,
      cmdoptions.constraints,
      cmdoptions.requirements,
      cmdoptions.editable,
      cmdoptions.find_links,
      cmdoptions.no_binary,
      cmdoptions.only_binary,
      cmdoptions.prefer_binary,
      cmdoptions.require_hashes,
      cmdoptions.pre,
      cmdoptions.trusted_host,
      cmdoptions.use_new_feature,
  ]
  
  # options to be passed to requirements
  SUPPORTED_OPTIONS_REQ: List[Callable[..., optparse.Option]] = [
      cmdoptions.install_options,
      cmdoptions.global_options,
      cmdoptions.hash,
  ]
  
  # the 'dest' string values
  SUPPORTED_OPTIONS_REQ_DEST = [str(o().dest) for o in SUPPORTED_OPTIONS_REQ]
  
  
  class ParsedRequirement:
      def __init__(
          self,
          requirement: str,
          is_editable: bool,
          comes_from: str,
          constraint: bool,
          options: Optional[Dict[str, Any]] = None,
          line_source: Optional[str] = None,
      ) -> None:
          self.requirement = requirement
          self.is_editable = is_editable
          self.comes_from = comes_from
          self.options = options
          self.constraint = constraint
          self.line_source = line_source
  
  
  class ParsedLine:
      def __init__(
          self,
          filename: str,
          lineno: int,
          args: str,
          opts: Values,
          constraint: bool,
      ) -> None:
          self.filename = filename
          self.lineno = lineno
          self.opts = opts
          self.constraint = constraint
  
          if args:
              self.is_requirement = True
              self.is_editable = False
              self.requirement = args
          elif opts.editables:
              self.is_requirement = True
              self.is_editable = True
              # We don't support multiple -e on one line
              self.requirement = opts.editables[0]
          else:
              self.is_requirement = False
  
  
  def parse_requirements(
      filename: str,
      session: PipSession,
      finder: Optional["PackageFinder"] = None,
      options: Optional[optparse.Values] = None,
      constraint: bool = False,
  ) -> Iterator[ParsedRequirement]:
      """Parse a requirements file and yield ParsedRequirement instances.
  
      :param filename:    Path or url of requirements file.
      :param session:     PipSession instance.
      :param finder:      Instance of pip.index.PackageFinder.
      :param options:     cli options.
      :param constraint:  If true, parsing a constraint file rather than
          requirements file.
      """
      line_parser = get_line_parser(finder)
      parser = RequirementsFileParser(session, line_parser)
  
      for parsed_line in parser.parse(filename, constraint):
          parsed_req = handle_line(
              parsed_line,
              options=options,
              finder=finder,
              session=session
          )
          if parsed_req is not None:
              yield parsed_req
  
  
  def preprocess(content: str) -> ReqFileLines:
      """Split, filter, and join lines, and return a line iterator
  
      :param content: the content of the requirements file
      """
      lines_enum: ReqFileLines = enumerate(content.splitlines(), start=1)
      lines_enum = join_lines(lines_enum)
      lines_enum = ignore_comments(lines_enum)
      lines_enum = expand_env_variables(lines_enum)
      return lines_enum
  
  
  def handle_requirement_line(
      line: ParsedLine,
      options: Optional[optparse.Values] = None,
  ) -> ParsedRequirement:
  
      # preserve for the nested code path
      line_comes_from = '{} {} (line {})'.format(
          '-c' if line.constraint else '-r', line.filename, line.lineno,
      )
  
      assert line.is_requirement
  
      if line.is_editable:
          # For editable requirements, we don't support per-requirement
          # options, so just return the parsed requirement.
          return ParsedRequirement(
              requirement=line.requirement,
              is_editable=line.is_editable,
              comes_from=line_comes_from,
              constraint=line.constraint,
          )
      else:
          if options:
              # Disable wheels if the user has specified build options
              cmdoptions.check_install_build_global(options, line.opts)
  
          # get the options that apply to requirements
          req_options = {}
          for dest in SUPPORTED_OPTIONS_REQ_DEST:
              if dest in line.opts.__dict__ and line.opts.__dict__[dest]:
                  req_options[dest] = line.opts.__dict__[dest]
  
          line_source = f'line {line.lineno} of {line.filename}'
          return ParsedRequirement(
              requirement=line.requirement,
              is_editable=line.is_editable,
              comes_from=line_comes_from,
              constraint=line.constraint,
              options=req_options,
              line_source=line_source,
          )
  
  
  def handle_option_line(
      opts: Values,
      filename: str,
      lineno: int,
      finder: Optional["PackageFinder"] = None,
      options: Optional[optparse.Values] = None,
      session: Optional[PipSession] = None,
  ) -> None:
  
      if options:
          # percolate options upward
          if opts.require_hashes:
              options.require_hashes = opts.require_hashes
          if opts.features_enabled:
              options.features_enabled.extend(
                  f for f in opts.features_enabled
                  if f not in options.features_enabled
              )
  
      # set finder options
      if finder:
          find_links = finder.find_links
          index_urls = finder.index_urls
          if opts.index_url:
              index_urls = [opts.index_url]
          if opts.no_index is True:
              index_urls = []
          if opts.extra_index_urls:
              index_urls.extend(opts.extra_index_urls)
          if opts.find_links:
              # FIXME: it would be nice to keep track of the source
              # of the find_links: support a find-links local path
              # relative to a requirements file.
              value = opts.find_links[0]
              req_dir = os.path.dirname(os.path.abspath(filename))
              relative_to_reqs_file = os.path.join(req_dir, value)
              if os.path.exists(relative_to_reqs_file):
                  value = relative_to_reqs_file
              find_links.append(value)
  
          if session:
              # We need to update the auth urls in session
              session.update_index_urls(index_urls)
  
          search_scope = SearchScope(
              find_links=find_links,
              index_urls=index_urls,
          )
          finder.search_scope = search_scope
  
          if opts.pre:
              finder.set_allow_all_prereleases()
  
          if opts.prefer_binary:
              finder.set_prefer_binary()
  
          if session:
              for host in opts.trusted_hosts or []:
                  source = f'line {lineno} of {filename}'
                  session.add_trusted_host(host, source=source)
  
  
  def handle_line(
      line: ParsedLine,
      options: Optional[optparse.Values] = None,
      finder: Optional["PackageFinder"] = None,
      session: Optional[PipSession] = None,
  ) -> Optional[ParsedRequirement]:
      """Handle a single parsed requirements line; This can result in
      creating/yielding requirements, or updating the finder.
  
      :param line:        The parsed line to be processed.
      :param options:     CLI options.
      :param finder:      The finder - updated by non-requirement lines.
      :param session:     The session - updated by non-requirement lines.
  
      Returns a ParsedRequirement object if the line is a requirement line,
      otherwise returns None.
  
      For lines that contain requirements, the only options that have an effect
      are from SUPPORTED_OPTIONS_REQ, and they are scoped to the
      requirement. Other options from SUPPORTED_OPTIONS may be present, but are
      ignored.
  
      For lines that do not contain requirements, the only options that have an
      effect are from SUPPORTED_OPTIONS. Options from SUPPORTED_OPTIONS_REQ may
      be present, but are ignored. These lines may contain multiple options
      (although our docs imply only one is supported), and all our parsed and
      affect the finder.
      """
  
      if line.is_requirement:
          parsed_req = handle_requirement_line(line, options)
          return parsed_req
      else:
          handle_option_line(
              line.opts,
              line.filename,
              line.lineno,
              finder,
              options,
              session,
          )
          return None
  
  
  class RequirementsFileParser:
      def __init__(
          self,
          session: PipSession,
          line_parser: LineParser,
      ) -> None:
          self._session = session
          self._line_parser = line_parser
  
      def parse(self, filename: str, constraint: bool) -> Iterator[ParsedLine]:
          """Parse a given file, yielding parsed lines.
          """
          yield from self._parse_and_recurse(filename, constraint)
  
      def _parse_and_recurse(
          self, filename: str, constraint: bool
      ) -> Iterator[ParsedLine]:
          for line in self._parse_file(filename, constraint):
              if (
                  not line.is_requirement and
                  (line.opts.requirements or line.opts.constraints)
              ):
                  # parse a nested requirements file
                  if line.opts.requirements:
                      req_path = line.opts.requirements[0]
                      nested_constraint = False
                  else:
                      req_path = line.opts.constraints[0]
                      nested_constraint = True
  
                  # original file is over http
                  if SCHEME_RE.search(filename):
                      # do a url join so relative paths work
                      req_path = urllib.parse.urljoin(filename, req_path)
                  # original file and nested file are paths
                  elif not SCHEME_RE.search(req_path):
                      # do a join so relative paths work
                      req_path = os.path.join(
                          os.path.dirname(filename), req_path,
                      )
  
                  yield from self._parse_and_recurse(req_path, nested_constraint)
              else:
                  yield line
  
      def _parse_file(self, filename: str, constraint: bool) -> Iterator[ParsedLine]:
          _, content = get_file_content(filename, self._session)
  
          lines_enum = preprocess(content)
  
          for line_number, line in lines_enum:
              try:
                  args_str, opts = self._line_parser(line)
              except OptionParsingError as e:
                  # add offending line
                  msg = f'Invalid requirement: {line}\n{e.msg}'
                  raise RequirementsFileParseError(msg)
  
              yield ParsedLine(
                  filename,
                  line_number,
                  args_str,
                  opts,
                  constraint,
              )
  
  
  def get_line_parser(finder: Optional["PackageFinder"]) -> LineParser:
      def parse_line(line: str) -> Tuple[str, Values]:
          # Build new parser for each line since it accumulates appendable
          # options.
          parser = build_parser()
          defaults = parser.get_default_values()
          defaults.index_url = None
          if finder:
              defaults.format_control = finder.format_control
  
          args_str, options_str = break_args_options(line)
  
          opts, _ = parser.parse_args(shlex.split(options_str), defaults)
  
          return args_str, opts
  
      return parse_line
  
  
  def break_args_options(line: str) -> Tuple[str, str]:
      """Break up the line into an args and options string.  We only want to shlex
      (and then optparse) the options, not the args.  args can contain markers
      which are corrupted by shlex.
      """
      tokens = line.split(' ')
      args = []
      options = tokens[:]
      for token in tokens:
          if token.startswith('-') or token.startswith('--'):
              break
          else:
              args.append(token)
              options.pop(0)
      return ' '.join(args), ' '.join(options)
  
  
  class OptionParsingError(Exception):
      def __init__(self, msg: str) -> None:
          self.msg = msg
  
  
  def build_parser() -> optparse.OptionParser:
      """
      Return a parser for parsing requirement lines
      """
      parser = optparse.OptionParser(add_help_option=False)
  
      option_factories = SUPPORTED_OPTIONS + SUPPORTED_OPTIONS_REQ
      for option_factory in option_factories:
          option = option_factory()
          parser.add_option(option)
  
      # By default optparse sys.exits on parsing errors. We want to wrap
      # that in our own exception.
      def parser_exit(self: Any, msg: str) -> "NoReturn":
          raise OptionParsingError(msg)
      # NOTE: mypy disallows assigning to a method
      #       https://github.com/python/mypy/issues/2427
      parser.exit = parser_exit  # type: ignore
  
      return parser
  
  
  def join_lines(lines_enum: ReqFileLines) -> ReqFileLines:
      """Joins a line ending in '\' with the previous line (except when following
      comments).  The joined line takes on the index of the first line.
      """
      primary_line_number = None
      new_line: List[str] = []
      for line_number, line in lines_enum:
          if not line.endswith('\\') or COMMENT_RE.match(line):
              if COMMENT_RE.match(line):
                  # this ensures comments are always matched later
                  line = ' ' + line
              if new_line:
                  new_line.append(line)
                  assert primary_line_number is not None
                  yield primary_line_number, ''.join(new_line)
                  new_line = []
              else:
                  yield line_number, line
          else:
              if not new_line:
                  primary_line_number = line_number
              new_line.append(line.strip('\\'))
  
      # last line contains \
      if new_line:
          assert primary_line_number is not None
          yield primary_line_number, ''.join(new_line)
  
      # TODO: handle space after '\'.
  
  
  def ignore_comments(lines_enum: ReqFileLines) -> ReqFileLines:
      """
      Strips comments and filter empty lines.
      """
      for line_number, line in lines_enum:
          line = COMMENT_RE.sub('', line)
          line = line.strip()
          if line:
              yield line_number, line
  
  
  def expand_env_variables(lines_enum: ReqFileLines) -> ReqFileLines:
      """Replace all environment variables that can be retrieved via `os.getenv`.
  
      The only allowed format for environment variables defined in the
      requirement file is `${MY_VARIABLE_1}` to ensure two things:
  
      1. Strings that contain a `$` aren't accidentally (partially) expanded.
      2. Ensure consistency across platforms for requirement files.
  
      These points are the result of a discussion on the `github pull
      request #3514 <https://github.com/pypa/pip/pull/3514>`_.
  
      Valid characters in variable names follow the `POSIX standard
      <http://pubs.opengroup.org/onlinepubs/9699919799/>`_ and are limited
      to uppercase letter, digits and the `_` (underscore).
      """
      for line_number, line in lines_enum:
          for env_var, var_name in ENV_VAR_RE.findall(line):
              value = os.getenv(var_name)
              if not value:
                  continue
  
              line = line.replace(env_var, value)
  
          yield line_number, line
  
  
  def get_file_content(url: str, session: PipSession) -> Tuple[str, str]:
      """Gets the content of a file; it may be a filename, file: URL, or
      http: URL.  Returns (location, content).  Content is unicode.
      Respects # -*- coding: declarations on the retrieved files.
  
      :param url:         File path or url.
      :param session:     PipSession instance.
      """
      scheme = get_url_scheme(url)
  
      # Pip has special support for file:// URLs (LocalFSAdapter).
      if scheme in ['http', 'https', 'file']:
          resp = session.get(url)
          raise_for_status(resp)
          return resp.url, resp.text
  
      # Assume this is a bare path.
      try:
          with open(url, 'rb') as f:
              content = auto_decode(f.read())
      except OSError as exc:
          raise InstallationError(f'Could not open requirements file: {exc}')
      return url, content
  