commands/envelope: refactor deriving headers to be edited

Split the code into its own function.
Make it properly case-insensitive.
Apply either the blacklist or the whitelist setting, trying to apply
both makes no sense.
Enforce that either a blacklist or a whitelist is configured in the
settings.

4 files changed, 51 insertions, 55 deletions

diff --git a/alot/commands/envelope.py b/alot/commands/envelope.py
index 5dce6b44..c347c3c7 100644
--- a/alot/commands/envelope.py
+++ b/alot/commands/envelope.py
@@ -26,7 +26,6 @@ from ..errors               import GPGProblem
 from ..settings.const       import settings
 from ..settings.errors      import NoMatchingAccount
 from ..utils                import argparse as cargparse
-from ..utils.collections    import OrderedSet
 
 
 MODE = 'envelope'
@@ -326,21 +325,41 @@ class EditCommand(Command):
         self.edit_only_body = False
         super().__init__(**kwargs)
 
+    def _headers_to_edit(self, headers):
+        whitelist = settings.get('edit_headers_whitelist')
+        blacklist = settings.get('edit_headers_blacklist')
+
+        # convert all header names to lowercase for uniqueness
+        wl = set(map(str.lower, whitelist))
+        bl = set(map(str.lower, blacklist))
+        kl = set(map(str.lower, headers))
+
+        # exactly one of wl/bl must be '*', so when operating
+        # in blacklist mode we convert the blacklist to whitelist
+        if '*' in wl:
+            wl = kl - bl
+
+        # drop all non-whitelisted headers
+        edit_headers = headers.copy()
+        for k in set((k.lower() for k in edit_headers)):
+            if not k in wl:
+                del edit_headers[k]
+
+        if not '*' in whitelist:
+            # any explicitly whitelisted headers that do not have a value
+            # are set to empty string, so they appear in the edited file
+            for h in whitelist:
+                if not h in edit_headers:
+                    edit_headers[h] = ''
+
+        logging.debug('editable headers: %s', edit_headers)
+        return edit_headers
+
     async def apply(self, ui):
         ebuffer = ui.current_buffer
         if not self.envelope:
             self.envelope = ui.current_buffer.envelope
 
-        # determine editable headers
-        edit_headers = OrderedSet(settings.get('edit_headers_whitelist'))
-        if '*' in edit_headers:
-            edit_headers = OrderedSet(self.envelope.headers)
-        blacklist = set(settings.get('edit_headers_blacklist'))
-        if '*' in blacklist:
-            blacklist = set(self.envelope.headers)
-        edit_headers = edit_headers - blacklist
-        logging.info('editable headers: %s', edit_headers)
-
         def openEnvelopeFromTmpfile():
             # This parses the input from the tempfile.
             # we do this ourselves here because we want to be able to
@@ -367,20 +386,15 @@ class EditCommand(Command):
 
         # decode header
         headertext = ''
-        for key in edit_headers:
-            vlist = self.envelope.get_all(key)
-            if len(vlist) == 0:
-                # ensure editable headers are present in template
-                vlist.append('')
-            else:
-                # remove to be edited lines from envelope
+        for key, val in self._headers_to_edit(self.envelope.headers).items():
+            # remove to be edited lines from envelope
+            if key in self.envelope:
                 del self.envelope[key]
 
-            for value in vlist:
-                # newlines (with surrounding spaces) by spaces in values
-                value = value.strip()
-                value = re.sub('[ \t\r\f\v]*\n[ \t\r\f\v]*', ' ', value)
-                headertext += '%s: %s\n' % (key, value)
+            # newlines (with surrounding spaces) by spaces in values
+            val = val.strip()
+            val = re.sub('[ \t\r\f\v]*\n[ \t\r\f\v]*', ' ', val)
+            headertext += '%s: %s\n' % (key, val)
 
         # determine editable content
         bodytext = self.envelope.body
diff --git a/alot/defaults/alot.rc.spec b/alot/defaults/alot.rc.spec
index 6531f76a..ca890eb6 100644
--- a/alot/defaults/alot.rc.spec
+++ b/alot/defaults/alot.rc.spec
@@ -114,9 +114,10 @@ editor_spawn = boolean(default=False)
 # will make alot non-blocking during edits
 editor_in_thread = boolean(default=False)
 
-# Which header fields should be editable in your editor
-# used are those that match the whitelist and don't match the blacklist.
-# in both cases '*' may be used to indicate all fields.
+# Which header fields should be editable in your editor.
+# Exactly one of edit_headers_whitelist and edit_headers_blacklist must be '*',
+# then the other one is used to either whitelist or blacklist headers for
+# editing.
 edit_headers_whitelist = force_list(default=list(*,))
 
 # see :ref:`edit_headers_whitelist <edit-headers-whitelist>`
diff --git a/alot/settings/manager.py b/alot/settings/manager.py
index f8ade6df..e4fa48d7 100644
--- a/alot/settings/manager.py
+++ b/alot/settings/manager.py
@@ -154,6 +154,16 @@ class SettingsManager:
         tempdir = self._config.get('template_dir')
         logging.debug('template directory: `%s`' % tempdir)
 
+        # validate edit_headers_whitelist/blacklist, which depend on each other
+        wl = self._config.get('edit_headers_whitelist')
+        bl = self._config.get('edit_headers_blacklist')
+        if (wl == ['*']) == (bl == ['*']):
+            raise ConfigError('Exactly one of "edit_headers_whitelist"',
+                              '"edit_headers_blacklist" must be "*"')
+        if ('*' in wl and len(wl) > 1) or ('*' in bl and len(bl) > 1):
+            raise ConfigError('When "*" is used in "edit_headers_whitelist"/'
+                              '"edit_headers_blacklist", it must be the only item.')
+
         # themes
         themestring = newconfig['theme']
         themes_dir = self._config.get('themes_dir')
diff --git a/alot/utils/collections.py b/alot/utils/collections.py
deleted file mode 100644
index acde56ce..00000000
--- a/alot/utils/collections.py
+++ /dev/null
@@ -1,29 +0,0 @@
-# This file is released under the GNU GPL, version 3 or a later revision.
-# For further details see the COPYING file
-
-from collections.abc import Set
-
-# for backward compatibility with Python <3.7
-from collections import OrderedDict
-
-
-class OrderedSet(Set):
-    """
-    Ordered collection of distinct hashable objects.
-    Taken from https://stackoverflow.com/a/10006674
-    """
-
-    def __init__(self, iterable=()):
-        self.d = OrderedDict.fromkeys(iterable)
-
-    def __len__(self):
-        return len(self.d)
-
-    def __contains__(self, element):
-        return element in self.d
-
-    def __iter__(self):
-        return iter(self.d)
-
-    def __repr__(self):
-        return str(list(self))