thread: optionally show per-message Subject in summary line

NEWS

@@ -1,3 +1,9 @@
+unreleased:
+* feature: new config setting "msg_summary_show_subject" to display each
+  message's Subject on its summary line in thread mode. The 'different'
+  mode shows the subject of a reply only when it diverges from its parent
+  message; (issue #566).
+
 0.12:
 * breaking: drop support for python 3.8, add support for python 3.13 & 3.14
 * deps: Increase required version of notmuch2 to 0.34.2

alot/db/message.py

@@ -69,6 +69,11 @@ def __init__(self, dbman, msg, thread=None):
         else:
             self._from = '"Unknown" <>'
 
+        try:
+            self._subject = decode_header(msg.header('Subject'))
+        except (NullPointerError, LookupError):
+            self._subject = ''
+
     def __str__(self):
         """prettyprint the message"""
         aname, aaddress = self.get_author()
@@ -174,6 +179,15 @@ def get_author(self):
         """
         return email.utils.parseaddr(self._from)
 
+    def get_subject(self):
+        """
+        returns the decoded :mailheader:`Subject` header for this message,
+        captured at construction time. Empty string if absent or unreadable.
+
+        :rtype: str
+        """
+        return self._subject
+
     def add_tags(self, tags, afterwards=None, remove_rest=False):
         """
         adds tags to message

alot/defaults/alot.rc.spec

@@ -292,6 +292,18 @@ envelope_html2txt = string(default=None)
 # messages in that thread.
 msg_summary_hides_threadwide_tags = boolean(default=True)
 
+# In a thread buffer, show each message's Subject on its summary line.
+# Valid values are:
+#
+# * 'never' (the default), do not show subjects in the summary
+# * 'always', always show the subject
+# * 'different', show the subject of each reply only when it differs from
+#   its parent message's subject after normalisation (localised reply/forward
+#   prefixes such as 'Re:', 'Fwd:', 'Aw:'... and ``[list-name]`` mailing-list
+#   tags are stripped before comparison). Root messages always show their
+#   subject in this mode, to provide thread context when the thread is folded.
+msg_summary_show_subject = option('never', 'always', 'different', default='never')
+
 # The list of headers to match to determine sending account for a reply.
 # Headers are searched in the order in which they are specified here, and the first header
 # containing a match is used. If multiple accounts match in that header, the one defined

alot/defaults/default.theme

@@ -43,6 +43,8 @@
         even = 'default','','white','light blue','white','#006'
         odd = 'default','','white','dark blue','white','#068'
         focus = 'standout','','white','light gray','#ff8','g58'
+        subject_even = 'default','','light gray','light blue','light gray','#006'
+        subject_odd = 'default','','light gray','dark blue','light gray','#068'
 
 [envelope]
     body = 'default','','light gray','default','light gray','default'

alot/defaults/theme.spec

@@ -64,6 +64,8 @@
         even = attrtriple
         odd = attrtriple
         focus = attrtriple
+        subject_even = attrtriple(default=None)
+        subject_odd = attrtriple(default=None)
 [envelope]
     body = attrtriple
     header = attrtriple

alot/helper.py

@@ -585,6 +585,34 @@ def get_xdg_env(env_name, fallback):
     return env if env else fallback
 
 
+_SUBJECT_PREFIX_RE = re.compile(
+    r'^\s*(?:'
+    r'(?:re|aw|wg|fwd|fw|tr|sv|vs|odp|rv|res|rif)'
+    r'\s*(?:\[\d+\])?\s*:'
+    r'|'
+    r'\[[^\]]+\]'
+    r')\s*',
+    re.IGNORECASE,
+)
+
+
+def normalize_subject(subject):
+    """Strip leading reply/forward prefixes and bracketed list tags from a
+    subject line.
+
+    Recognises common localised prefixes (en/de/fr/it/es/pl/no/da/fi/nl) plus
+    the ``Re[2]:`` counter form, and ``[list-name]`` style mailing-list tags.
+    Stripping is recursive, case-insensitive and whitespace-tolerant, so
+    ``"Re: [list] Re: Hello"`` and ``"[list] Re: Hello"`` both reduce to
+    ``"Hello"``. This matches the way notmuch normalises thread subjects.
+    """
+    prev = None
+    while subject and subject != prev:
+        prev = subject
+        subject = _SUBJECT_PREFIX_RE.sub('', subject).strip()
+    return subject
+
+
 def get_notmuch_config_path():
     """ Find the notmuch config file via env vars and default locations """
     # This code is modeled after the description in nomtuch-config(1)

alot/widgets/thread.py

@@ -16,7 +16,7 @@
 from ..settings.const import settings
 from ..db.attachment import Attachment
 from ..db.utils import decode_header, X_SIGNATURE_MESSAGE_HEADER
-from ..helper import string_sanitize
+from ..helper import string_sanitize, normalize_subject
 
 ANSI_BACKGROUND = settings.get("interpret_ansi_background")
 
@@ -26,12 +26,17 @@ class MessageSummaryWidget(urwid.WidgetWrap):
     one line summary of a :class:`~alot.db.message.Message`.
     """
 
-    def __init__(self, message, even=True):
+    def __init__(self, message, even=True, parent_message=None):
         """
         :param message: a message
         :type message: alot.db.Message
         :param even: even entry in a pile of messages? Used for theming.
         :type even: bool
+        :param parent_message: the message this is a reply to, or ``None`` if
+            this is a root of the thread. Used by the ``'different'``
+            mode of ``msg_summary_show_subject`` to decide whether to show
+            the subject; root messages always show their subject.
+        :type parent_message: alot.db.Message or None
         """
         self.message = message
         self.even = even
@@ -47,6 +52,26 @@ def __init__(self, message, even=True):
         txt = urwid.Text(sumstr)
         cols.append(txt)
 
+        subject_mode = settings.get('msg_summary_show_subject')
+        if subject_mode != 'never':
+            msg_subject = message.get_subject() or ''
+            show_subject = False
+            if subject_mode == 'always':
+                show_subject = bool(msg_subject)
+            elif subject_mode == 'different':
+                if parent_message is None:
+                    show_subject = bool(msg_subject)
+                else:
+                    parent_subject = parent_message.get_subject() or ''
+                    show_subject = (normalize_subject(msg_subject)
+                                    != normalize_subject(parent_subject))
+            if show_subject:
+                subj_attr = settings.get_theming_attribute(
+                    'thread', 'summary',
+                    'subject_even' if even else 'subject_odd')
+                cols.append(urwid.Text((subj_attr, msg_subject),
+                                       wrap='ellipsis'))
+
         if settings.get('msg_summary_hides_threadwide_tags'):
             thread_tags = message.get_thread().get_tags(intersection=True)
             outstanding_tags = set(message.get_tags()).difference(thread_tags)
@@ -158,15 +183,21 @@ class MessageTree(CollapsibleTree):
 
     Collapsing this message corresponds to showing the summary only.
     """
-    def __init__(self, message, odd=True):
+    def __init__(self, message, odd=True, parent_message=None):
         """
         :param message: Message to display
         :type message: alot.db.Message
         :param odd: theme summary widget as if this is an odd line
                     (in the message-pile)
         :type odd: bool
+        :param parent_message: the message ``message`` is a reply to, or
+            ``None`` if this is a thread root. Forwarded to
+            :class:`MessageSummaryWidget` so 'different' mode can compare
+            the subject against the actual parent.
+        :type parent_message: alot.db.Message or None
         """
         self._message = message
+        self._parent_message = parent_message
         self._odd = odd
         self.display_source = False
         self._summaryw = None
@@ -252,7 +283,8 @@ def collapse_if_matches(self, querystring):
     def _get_summary(self):
         if self._summaryw is None:
             self._summaryw = MessageSummaryWidget(
-                self._message, even=(not self._odd))
+                self._message, even=(not self._odd),
+                parent_message=self._parent_message)
         return self._summaryw
 
     def _get_source(self):
@@ -382,10 +414,10 @@ def __init__(self, thread):
         self._prev_sibling_of = {}
         self._message = {}
 
-        def accumulate(msg, odd=True):
+        def accumulate(msg, odd=True, parent=None):
             """recursively read msg and its replies"""
             mid = msg.get_message_id()
-            self._message[mid] = MessageTree(msg, odd)
+            self._message[mid] = MessageTree(msg, odd, parent_message=parent)
             odd = not odd
             last = None
             self._first_child_of[mid] = None
@@ -397,7 +429,7 @@ def accumulate(msg, odd=True):
                 self._prev_sibling_of[rid] = last
                 self._next_sibling_of[last] = rid
                 last = rid
-                odd = accumulate(reply, odd)
+                odd = accumulate(reply, odd, parent=msg)
             self._last_child_of[mid] = last
             return odd
 

docs/source/configuration/alotrc_table

@@ -439,6 +439,25 @@
     :default: True
 
 
+.. _msg-summary-show-subject:
+
+.. describe:: msg_summary_show_subject
+
+     In a thread buffer, show each message's Subject on its summary line.
+     Valid values are:
+
+     * 'never' (the default), do not show subjects in the summary
+     * 'always', always show the subject
+     * 'different', show the subject of each reply only when it differs from
+       its parent message's subject after normalisation (localised reply/forward
+       prefixes such as 'Re:', 'Fwd:', 'Aw:'... and ``[list-name]`` mailing-list
+       tags are stripped before comparison). Root messages always show their
+       subject in this mode, to provide thread context when the thread is folded.
+
+    :type: option, one of ['never', 'always', 'different']
+    :default: never
+
+
 .. _namedqueries-statusbar:
 
 .. describe:: namedqueries_statusbar

tests/db/test_message.py

@@ -120,3 +120,23 @@ def test_get_author_no_name(self):
                         mock.Mock(return_value=[acc])):
             msg = message.Message(mock.Mock(), MockNotmuchMessage())
         self.assertEqual(msg.get_author(), ('Unknown', ''))
+
+    def test_get_subject_missing(self):
+        """Message.get_subject() returns the empty string when the Subject
+        header is absent."""
+        msg = message.Message(mock.Mock(), MockNotmuchMessage())
+        self.assertEqual(msg.get_subject(), '')
+
+    def test_get_subject_plain(self):
+        """Message.get_subject() returns the Subject header verbatim when
+        no encoding is involved."""
+        msg = message.Message(
+            mock.Mock(), MockNotmuchMessage({'Subject': 'Hello world'}))
+        self.assertEqual(msg.get_subject(), 'Hello world')
+
+    def test_get_subject_rfc2047(self):
+        """Message.get_subject() decodes RFC 2047 encoded-words."""
+        msg = message.Message(
+            mock.Mock(),
+            MockNotmuchMessage({'Subject': '=?utf-8?Q?H=C3=A9?='}))
+        self.assertEqual(msg.get_subject(), 'Hé')

tests/settings/test_manager.py

@@ -83,6 +83,33 @@ def test_read_config_doesnt_exist(self):
 
         manager.get_theming_attribute('global', 'body')
 
+    def test_thread_summary_subject_even_odd_theming_present(self):
+        """The default theme must define 'subject_even' and 'subject_odd'
+        attributes under thread.summary so the widget can colour the
+        subject column with a background matching the alternating
+        even/odd row backgrounds."""
+        with tempfile.NamedTemporaryFile(mode='w+', delete=False) as f:
+            f.write('')
+        self.addCleanup(os.unlink, f.name)
+        manager = SettingsManager()
+        manager.read_config(f.name)
+        even_attr = manager.get_theming_attribute(
+            'thread', 'summary', 'subject_even')
+        odd_attr = manager.get_theming_attribute(
+            'thread', 'summary', 'subject_odd')
+        self.assertIsNotNone(even_attr)
+        self.assertIsNotNone(odd_attr)
+
+    def test_msg_summary_show_subject_default_never(self):
+        """The msg_summary_show_subject option defaults to 'never' so the
+        thread view stays unchanged for users who don't opt in."""
+        with tempfile.NamedTemporaryFile(mode='w+', delete=False) as f:
+            f.write('')
+        self.addCleanup(os.unlink, f.name)
+        manager = SettingsManager()
+        manager.read_config(f.name)
+        self.assertEqual(manager.get('msg_summary_show_subject'), 'never')
+
     def test_unknown_settings_in_config_are_logged(self):
         # todo: For py3, don't mock the logger, use assertLogs
         unknown_settings = ['templates_dir', 'unknown_section', 'unknown_1',

tests/test_helper.py

@@ -481,3 +481,57 @@ def test_parsing_working(self):
                      'Subject': ['Re: Hello'],
                      'In-reply-to': ['<C8CE9EFD-CB23-4BC0-B70D-9B7FEAD59F8C@example.org>']}, '')
         self.assertEqual(actual, expected)
+
+
+class TestNormalizeSubject(unittest.TestCase):
+
+    def test_empty(self):
+        self.assertEqual(helper.normalize_subject(''), '')
+
+    def test_no_prefix(self):
+        self.assertEqual(helper.normalize_subject('Hello'), 'Hello')
+
+    def test_re_prefix(self):
+        self.assertEqual(helper.normalize_subject('Re: Hello'), 'Hello')
+
+    def test_case_insensitive(self):
+        self.assertEqual(helper.normalize_subject('RE:  Hello'), 'Hello')
+        self.assertEqual(helper.normalize_subject('rE: Hello'), 'Hello')
+
+    def test_recursive(self):
+        self.assertEqual(
+            helper.normalize_subject('Re: Re: Re: Hello'), 'Hello')
+
+    def test_mixed_recursive(self):
+        self.assertEqual(
+            helper.normalize_subject('Fwd: Re: Aw: Hello'), 'Hello')
+
+    def test_localized_prefixes(self):
+        for prefix in ('Fwd', 'Fw', 'Aw', 'Wg', 'Tr', 'Sv', 'Vs',
+                       'Odp', 'Rv', 'Res', 'Rif'):
+            with self.subTest(prefix=prefix):
+                self.assertEqual(
+                    helper.normalize_subject(f'{prefix}: Hello'), 'Hello')
+
+    def test_strips_leading_list_tag(self):
+        self.assertEqual(
+            helper.normalize_subject('[list-name] Hello'), 'Hello')
+
+    def test_strips_re_then_list(self):
+        self.assertEqual(
+            helper.normalize_subject('Re: [list-name] Hello'), 'Hello')
+
+    def test_strips_list_then_re(self):
+        self.assertEqual(
+            helper.normalize_subject('[list-name] Re: Hello'), 'Hello')
+
+    def test_strips_multiple_list_tags(self):
+        self.assertEqual(
+            helper.normalize_subject('[list] [other] Hello'), 'Hello')
+
+    def test_counter_form(self):
+        self.assertEqual(helper.normalize_subject('Re[2]: Hello'), 'Hello')
+
+    def test_strips_whitespace(self):
+        self.assertEqual(helper.normalize_subject('   Re:  Hello   '),
+                         'Hello')