Tag browser: Fix using F2 to edit items not allowing completion

Also fixes incorrect completion data when using F2 after using rename on
an item from another category.

Rather than setting the completion data in the context menu handler,
load it when actually creating the editor.

src/calibre/gui2/tag_browser/view.py

@@ -5,24 +5,31 @@ __license__   = 'GPL v3'
 __copyright__ = '2011, Kovid Goyal <kovid@kovidgoyal.net>'
 __docformat__ = 'restructuredtext en'
 
-import os, re, traceback
+import os
+import re
+import traceback
+from contextlib import suppress
 from functools import partial
-
 from qt.core import (
-    QStyledItemDelegate, Qt, QTreeView, pyqtSignal, QSize, QIcon, QApplication, QStyle, QAbstractItemView,
+    QAbstractItemView, QApplication, QBrush, QColor, QCursor, QDrag, QFont, QIcon,
-    QMenu, QPoint, QToolTip, QCursor, QDrag, QRect, QModelIndex, QPointF, QStyleOptionViewItem,
+    QLinearGradient, QMenu, QModelIndex, QPalette, QPen, QPoint, QPointF, QRect, QSize,
-    QLinearGradient, QPalette, QColor, QPen, QBrush, QFont, QTimer
+    QStyle, QStyledItemDelegate, QStyleOptionViewItem, Qt, QTimer, QToolTip, QTreeView,
+    pyqtSignal,
 )
 
 from calibre import sanitize_file_name
 from calibre.constants import config_dir
 from calibre.ebooks.metadata import rating_to_stars
+from calibre.gui2 import (
+    FunctionDispatcher, choose_files, config, empty_index, gprefs, pixmap_to_data,
+    question_dialog, rating_font,
+)
 from calibre.gui2.complete2 import EditWithComplete
-from calibre.gui2.tag_browser.model import (TagTreeItem, TAG_SEARCH_STATES,
+from calibre.gui2.tag_browser.model import (
-        TagsModel, DRAG_IMAGE_ROLE, COUNT_ROLE, rename_only_in_vl_question)
+    COUNT_ROLE, DRAG_IMAGE_ROLE, TAG_SEARCH_STATES, TagsModel, TagTreeItem,
+    rename_only_in_vl_question,
+)
 from calibre.gui2.widgets import EnLineEdit
-from calibre.gui2 import (config, gprefs, choose_files, pixmap_to_data,
-                          rating_font, empty_index, question_dialog, FunctionDispatcher)
 from calibre.utils.icu import sort_key
 from calibre.utils.serialize import json_loads
 
@@ -34,7 +41,6 @@ class TagDelegate(QStyledItemDelegate):  # {{{
         self.old_look = False
         self.rating_pat = re.compile(r'[%s]' % rating_to_stars(3, True))
         self.rating_font = QFont(rating_font())
-        self.completion_data = None
         self.tags_view = tags_view
 
     def draw_average_rating(self, item, style, painter, option, widget):
@@ -123,9 +129,6 @@ class TagDelegate(QStyledItemDelegate):  # {{{
         if item.type == TagTreeItem.TAG and item.tag.state == 0 and config['show_avg_rating']:
             self.draw_average_rating(item, style, painter, option, widget)
 
-    def set_completion_data(self, data):
-        self.completion_data = data
-
     def createEditor(self, parent, option, index):
         item = self.tags_view.model().get_node(index)
         if not item.ignore_vl:
@@ -143,10 +146,19 @@ class TagDelegate(QStyledItemDelegate):  # {{{
                                     yes_text=_('Yes, apply in entire library'),
                                     no_text=_('No, apply only in Virtual library'),
                                     skip_dialog_name='tag_item_rename_in_entire_library')
-        if self.completion_data:
+        key, completion_data = '', None
+        if item.type == TagTreeItem.CATEGORY:
+            key = item.category_key
+        elif item.type == TagTreeItem.TAG:
+            key = getattr(item.tag, 'category', '')
+        if key:
+            from calibre.gui2.ui import get_gui
+            with suppress(Exception):
+                completion_data = get_gui().current_db.new_api.all_field_names(key)
+        if completion_data:
             editor = EditWithComplete(parent)
             editor.set_separator(None)
-            editor.update_items_cache(self.completion_data)
+            editor.update_items_cache(completion_data)
         else:
             editor = EnLineEdit(parent)
         return editor
@@ -546,25 +558,16 @@ class TagsView(QTreeView):  # {{{
                 self.recount()
                 return
 
-            def set_completion_data(category):
-                try:
-                    completion_data = self.db.new_api.all_field_names(category)
-                except:
-                    completion_data = None
-                self.itemDelegate().set_completion_data(completion_data)
-
             if action == 'edit_item_no_vl':
                 item = self.model().get_node(index)
                 item.use_vl = False
                 item.ignore_vl = ignore_vl
-                set_completion_data(category)
                 self.edit(index)
                 return
             if action == 'edit_item_in_vl':
                 item = self.model().get_node(index)
                 item.use_vl = True
                 item.ignore_vl = ignore_vl
-                set_completion_data(category)
                 self.edit(index)
                 return
             if action == 'delete_item_in_vl':