python · bob1de · May 21, 2017 · Aug 22, 2017 · Aug 27, 2017 · Aug 29, 2017
@@ -141,6 +141,7 @@ ArgumentParser objects
                           epilog=None, parents=[], \
                           formatter_class=argparse.HelpFormatter, \
                           prefix_chars='-', fromfile_prefix_chars=None, \
+                          fromfile_parent_relative=False, \
                           argument_default=None, conflict_handler='error', \
                           add_help=True, allow_abbrev=True)
 
@@ -168,6 +169,11 @@ ArgumentParser objects
    * fromfile_prefix_chars_ - The set of characters that prefix files from
      which additional arguments should be read (default: ``None``)
 
+   * fromfile_parent_relative_ - Whether to treat paths of included
+     argument files as relative to the location of the file they
+     are specified in (``True``) or to the current working directory
+     (``False``) (default: ``False``)
+
    * argument_default_ - The global default value for arguments
      (default: ``None``)
 
@@ -182,6 +188,9 @@ ArgumentParser objects
    .. versionchanged:: 3.5
       *allow_abbrev* parameter was added.
 
+   .. versionchanged:: TODO
+      *fromfile_parent_relative* parameter was added.
+
 The following sections describe how each of these are used.
 
 
@@ -489,7 +498,7 @@ disallowed.
 fromfile_prefix_chars
 ^^^^^^^^^^^^^^^^^^^^^
 
-Sometimes, for example when dealing with a particularly long argument lists, it
+Sometimes, for example when dealing with a particularly long argument list, it
 may make sense to keep the list of arguments in a file rather than typing it out
 at the command line.  If the ``fromfile_prefix_chars=`` argument is given to the
 :class:`ArgumentParser` constructor, then arguments that start with any of the
@@ -509,10 +518,26 @@ were in the same place as the original file referencing argument on the command
 line.  So in the example above, the expression ``['-f', 'foo', '@args.txt']``
 is considered equivalent to the expression ``['-f', 'foo', '-f', 'bar']``.
 
+Including argument files recursively is fine, as long as no infinite
+loops are produced.
+
 The ``fromfile_prefix_chars=`` argument defaults to ``None``, meaning that
 arguments will never be treated as file references.
 
 
+fromfile_parent_relative
+^^^^^^^^^^^^^^^^^^^^^^^^
+
+Before Python TODO, paths were always considered to be relative to the
+current working directory.  Now, when a file to include is specified
+inside another one, its path can be treated as being relative to
+the file it is contained in. To activate this behaviour, set the
+``fromfile_parent_relative=`` parameter to ``True``.  However, specifying
+absolute paths is and has always been possible as well.
+
+.. versionadded:: TODO
+
+
 argument_default
 ^^^^^^^^^^^^^^^^
 

@@ -1591,6 +1591,9 @@ class ArgumentParser(_AttributeHolder, _ActionsContainer):
         - prefix_chars -- Characters that prefix optional arguments
         - fromfile_prefix_chars -- Characters that prefix files containing
             additional arguments
+        - fromfile_parent_relative -- Whether to treat paths of included
+            files as relative to the place they were included from or the
+            current working directory
         - argument_default -- The default value for all arguments
         - conflict_handler -- String indicating how to handle conflicts
         - add_help -- Add a -h/-help option
@@ -1606,6 +1609,7 @@ def __init__(self,
                  formatter_class=HelpFormatter,
                  prefix_chars='-',
                  fromfile_prefix_chars=None,
+                 fromfile_parent_relative=False,
                  argument_default=None,
                  conflict_handler='error',
                  add_help=True,
@@ -1626,6 +1630,7 @@ def __init__(self,
         self.epilog = epilog
         self.formatter_class = formatter_class
         self.fromfile_prefix_chars = fromfile_prefix_chars
+        self.fromfile_parent_relative = fromfile_parent_relative
         self.add_help = add_help
         self.allow_abbrev = allow_abbrev
 
@@ -2025,18 +2030,28 @@ def _read_args_from_files(self, arg_strings):
 
             # replace arguments referencing files with the file content
             else:
+                arg_strings = []
+
                 try:
                     with open(arg_string[1:]) as args_file:
-                        arg_strings = []
                         for arg_line in args_file.read().splitlines():
                             for arg in self.convert_arg_line_to_args(arg_line):
+                                # make nested includes relative to their parent
+                                if self.fromfile_parent_relative and \
+                                   arg.startswith(self.fromfile_prefix_chars):
+                                    dirname = _os.path.dirname(arg_string[1:])
+                                    path = _os.path.join(dirname, arg[1:])
+                                    # eliminate ../a/../a constructs
+                                    path = _os.path.normpath(path)
+                                    arg = arg[0] + path
                                 arg_strings.append(arg)
-                        arg_strings = self._read_args_from_files(arg_strings)
-                        new_arg_strings.extend(arg_strings)
                 except OSError:
                     err = _sys.exc_info()[1]
                     self.error(str(err))
 
+                arg_strings = self._read_args_from_files(arg_strings)
+                new_arg_strings.extend(arg_strings)
+
         # return the modified argument list
         return new_arg_strings
 

diff --git a/Misc/NEWS.d/next/Library/2017-08-27-10-57-44.bpo-30421.ZjA80L.rst b/Misc/NEWS.d/next/Library/2017-08-27-10-57-44.bpo-30421.ZjA80L.rst
@@ -0,0 +1,3 @@
+Added fromfile_parent_relative parameter to argparse.ArgumentParser to
+allow paths of included argument files to be relative to the file they
+were included by.