bpo12806: Add argparse FlexiHelpFormatter

Author: davesteele

Doc/library/argparse.rst

@@ -295,11 +295,13 @@ classes:
 
 .. class:: RawDescriptionHelpFormatter
            RawTextHelpFormatter
+           FlexiHelpFormatter
            ArgumentDefaultsHelpFormatter
            MetavarTypeHelpFormatter
 
-:class:`RawDescriptionHelpFormatter` and :class:`RawTextHelpFormatter` give
-more control over how textual descriptions are displayed.
+:class:`RawDescriptionHelpFormatter`, :class:`RawTextHelpFormatter`, and
+:class:`FlexiHelpFormatter` give more control over how textual descriptions
+are displayed.
 By default, :class:`ArgumentParser` objects line-wrap the description_ and
 epilog_ texts in command-line help messages::
 
@@ -354,6 +356,57 @@ including argument descriptions. However, multiple newlines are replaced with
 one. If you wish to preserve multiple blank lines, add spaces between the
 newlines.
 
+:class:`FlexiHelpFormatter` wraps description and help text like the default
+formatter, while preserving paragraphs and supporting bulleted lists. Bullet
+list items are marked by the use of the "*", "-", "+", or ">" characters, or a
+single non-whitespace character followed by a "."::
+
+   >>> parser = argparse.ArgumentParser(
+   ...     prog='PROG',
+   ...     formatter_class=argparse.FlexiHelpFormatter,
+   ...     description="""
+   ...         The FlexiHelpFormatter will wrap text within paragraphs
+   ...         when required to in order to make the text fit.
+   ...
+   ...         Paragraphs are preserved.
+   ...
+   ...         It also supports bulleted lists in a number of formats:
+   ...           * stars
+   ...           1. numbers
+   ...           - ... and so on
+   ...         """)
+   >>> parser.add_argument(
+   ...     "argument",
+   ...     help="""
+   ...         Argument help text also supports flexible formatting,
+   ...         with word wrap:
+   ...             * See?
+   ...         """)
+   >>> parser.print_help()
+   usage: PROG [-h] option
+
+   The FlexiHelpFormatter will wrap text within paragraphs when required to in
+   order to make the text fit.
+
+   Paragraphs are preserved.
+
+   It also supports bulleted lists in a number of formats:
+     * stars
+     1. numbers
+     - ... and so on
+
+   positional arguments:
+     argument    Argument help text also supports flexible formatting, with word
+                 wrap:
+                     * See?
+
+   optional arguments:
+     -h, --help  show this help message and exit
+
+
+.. versionchanged:: 3.9
+   :class:`FlexiHelpFormatter` class was added.
+
 :class:`ArgumentDefaultsHelpFormatter` automatically adds information about
 default values to each of the argument help messages::
 

Lib/argparse.py

@@ -75,6 +75,7 @@
     'ArgumentDefaultsHelpFormatter',
     'RawDescriptionHelpFormatter',
     'RawTextHelpFormatter',
+    'FlexiHelpFormatter',
     'MetavarTypeHelpFormatter',
     'Namespace',
     'Action',
@@ -513,7 +514,10 @@ def _format_action(self, action):
                 help_lines = self._split_lines(help_text, help_width)
                 parts.append('%*s%s\n' % (indent_first, '', help_lines[0]))
                 for line in help_lines[1:]:
-                    parts.append('%*s%s\n' % (help_position, '', line))
+                    if line.strip():
+                        parts.append('%*s%s\n' % (help_position, '', line))
+                    else:
+                        parts.append("\n")
 
         # or add a newline if the description doesn't end with one
         elif not action_header.endswith('\n'):
@@ -659,6 +663,82 @@ def _split_lines(self, text, width):
         return text.splitlines()
 
 
+class FlexiHelpFormatter(HelpFormatter):
+    """Help message formatter which respects paragraphs and bulleted lists.
+
+    Only the name of this class is considered a public API. All the methods
+    provided by the class are considered an implementation detail.
+    """
+
+    def _split_lines(self, text, width):
+        return self._para_reformat(text, width)
+
+    def _fill_text(self, text, width, indent):
+        lines = self._para_reformat(text, width)
+        return "\n".join(lines)
+
+    def _indents(self, line):
+        """Return line indent level and "sub_indent" for bullet list text."""
+
+        indent = len(_re.match(r"( *)", line).group(1))
+        list_match = _re.match(r"( *)(([*-+>]+|\w+\)|\w+\.) +)", line)
+        if list_match:
+            sub_indent = indent + len(list_match.group(2))
+        else:
+            sub_indent = indent
+
+        return (indent, sub_indent)
+
+    def _split_paragraphs(self, text):
+        """Split text in to paragraphs of like-indented lines."""
+
+        import textwrap
+
+        text = textwrap.dedent(text).strip()
+        text = _re.sub("\n\n[\n]+", "\n\n", text)
+
+        last_sub_indent = None
+        paragraphs = list()
+        for line in text.splitlines():
+            (indent, sub_indent) = self._indents(line)
+            is_text = len(line.strip()) > 0
+
+            if is_text and indent == sub_indent == last_sub_indent:
+                paragraphs[-1] += " " + line
+            else:
+                paragraphs.append(line)
+
+            if is_text:
+                last_sub_indent = sub_indent
+            else:
+                last_sub_indent = None
+
+        return paragraphs
+
+    def _para_reformat(self, text, width):
+        """Reformat text, by paragraph."""
+
+        import textwrap
+
+        lines = list()
+        for paragraph in self._split_paragraphs(text):
+
+            (indent, sub_indent) = self._indents(paragraph)
+
+            paragraph = self._whitespace_matcher.sub(" ", paragraph).strip()
+            new_lines = textwrap.wrap(
+                text=paragraph,
+                width=width,
+                initial_indent=" " * indent,
+                subsequent_indent=" " * sub_indent,
+            )
+
+            # Blank lines get eaten by textwrap, put it back
+            lines.extend(new_lines or [""])
+
+        return lines
+
+
 class ArgumentDefaultsHelpFormatter(HelpFormatter):
     """Help message formatter which adds default values to argument help.
 

Lib/test/test_argparse.py

@@ -5272,6 +5272,73 @@ class TestHelpRawDescription(HelpTestCase):
     version = ''
 
 
+class TestHelpFlexi(HelpTestCase):
+    """Test the FlexiHelpFormatter"""
+
+    parser_signature = Sig(
+        prog='PROG', formatter_class=argparse.FlexiHelpFormatter,
+        description='This text should be wrapped as appropriate to keep\n'
+                    'things nice and very, very tidy.\n'
+                    '\n'
+                    'Paragraphs should be preserved.\n'
+                    '    * bullet list items\n'
+                    '      should wrap to an appropriate place,\n'
+                    '      should such wrapping be required.\n'
+                    '    * short bullet\n'
+    )
+
+    argument_signatures = [
+        Sig('--foo', help='    foo help should also\n'
+                          'appear as given here\n'
+                          '\n'
+                          'along with a second paragraph, if called for\n'
+                          '  * bullet'),
+        Sig('spam', help='spam help'),
+    ]
+    argument_group_signatures = [
+        (Sig('title', description='short help text\n'
+                                  '\n'
+                                  'Longer help text, containing useful\n'
+                                  'contextual information for the var in\n'
+                                  'question\n'
+                                  '* and a bullet\n'),
+            [Sig('--bar', help='bar help')]),
+    ]
+    usage = '''\
+        usage: PROG [-h] [--foo FOO] [--bar BAR] spam
+        '''
+    help = usage + '''\
+
+        This text should be wrapped as appropriate to keep things nice and very, very
+        tidy.
+
+        Paragraphs should be preserved.
+            * bullet list items should wrap to an appropriate place, should such
+              wrapping be required.
+            * short bullet
+
+        positional arguments:
+          spam        spam help
+
+        optional arguments:
+          -h, --help  show this help message and exit
+          --foo FOO   foo help should also appear as given here
+
+                      along with a second paragraph, if called for
+                        * bullet
+
+        title:
+        short help text
+
+        Longer help text, containing useful contextual information for the var in
+        question
+        * and a bullet
+
+          --bar BAR   bar help
+        '''
+    version = ''
+
+
 class TestHelpArgumentDefaults(HelpTestCase):
     """Test the ArgumentDefaultsHelpFormatter"""
 

Misc/NEWS.d/next/Library/2020-09-07-00-00-51.bpo-12806.j1A_9o.rst

@@ -0,0 +1,3 @@
+The :mod:`argparse` module has a new :class:`argparse.FlexiHelpFormatter`
+class that wraps help and description text while preserving paragraphs and
+supporting bulleted lists.