From 56c0102d20adcaf9ff278126536f4275ef35aac4 Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Sat, 22 Feb 2020 09:25:45 +0530
Subject: [PATCH] When running Edit book on a book with no formats ask if an
 empty book should be created. Fixes #1864234 [[Enhancement] Add option to
 open Edit book even if the selected book is not an EPUB or
 AZW3](https://bugs.launchpad.net/calibre/+bug/1864234)

---
 src/calibre/gui2/actions/add.py        | 24 ++++++++++++++----------
 src/calibre/gui2/actions/tweak_epub.py | 22 ++++++++++++++++------
 2 files changed, 30 insertions(+), 16 deletions(-)

diff --git a/src/calibre/gui2/actions/add.py b/src/calibre/gui2/actions/add.py
index 97f23c3e5f..c22d5d2bf5 100644
--- a/src/calibre/gui2/actions/add.py
+++ b/src/calibre/gui2/actions/add.py
@@ -232,21 +232,25 @@ class AddAction(InterfaceAction):
                         return
 
         for id_ in ids:
-            from calibre.ebooks.oeb.polish.create import create_book
-            pt = PersistentTemporaryFile(suffix='.' + format_)
-            pt.close()
-            try:
-                mi = db.new_api.get_metadata(id_, get_cover=False,
-                                    get_user_categories=False, cover_as_data=False)
-                create_book(mi, pt.name, fmt=format_)
-                db.add_format_with_hooks(id_, format_, pt.name, index_is_id=True, notify=True)
-            finally:
-                os.remove(pt.name)
+            self.add_empty_format_to_book(id_, format_)
 
         current_idx = self.gui.library_view.currentIndex()
         if current_idx.isValid():
             view.model().current_changed(current_idx, current_idx)
 
+    def add_empty_format_to_book(self, book_id, fmt):
+        from calibre.ebooks.oeb.polish.create import create_book
+        db = self.gui.current_db
+        pt = PersistentTemporaryFile(suffix='.' + fmt.lower())
+        pt.close()
+        try:
+            mi = db.new_api.get_metadata(book_id, get_cover=False,
+                                get_user_categories=False, cover_as_data=False)
+            create_book(mi, pt.name, fmt=fmt.lower())
+            db.add_format_with_hooks(book_id, fmt, pt.name, index_is_id=True, notify=True)
+        finally:
+            os.remove(pt.name)
+
     def add_archive(self, single):
         paths = choose_files(
             self.gui, 'recursive-archive-add', _('Choose archive file'),
diff --git a/src/calibre/gui2/actions/tweak_epub.py b/src/calibre/gui2/actions/tweak_epub.py
index b8cfd8b1ce..d4c343cf6f 100644
--- a/src/calibre/gui2/actions/tweak_epub.py
+++ b/src/calibre/gui2/actions/tweak_epub.py
@@ -10,7 +10,7 @@ import time
 
 from PyQt5.Qt import QTimer, QDialog, QDialogButtonBox, QCheckBox, QVBoxLayout, QLabel, Qt
 
-from calibre.gui2 import error_dialog
+from calibre.gui2 import error_dialog, question_dialog
 from calibre.gui2.actions import InterfaceAction
 
 
@@ -105,13 +105,23 @@ class TweakEpubAction(InterfaceAction):
         from calibre.ebooks.oeb.polish.main import SUPPORTED
         db = self.gui.library_view.model().db
         fmts = db.formats(book_id, index_is_id=True) or ''
-        fmts = [x.upper().strip() for x in fmts.split(',')]
+        fmts = [x.upper().strip() for x in fmts.split(',') if x]
         tweakable_fmts = set(fmts).intersection(SUPPORTED)
         if not tweakable_fmts:
-            return error_dialog(self.gui, _('Cannot edit book'),
-                    _('The book must be in the %s formats to edit.'
-                        '\n\nFirst convert the book to one of these formats.') % (_(' or ').join(SUPPORTED)),
-                    show=True)
+            if not fmts:
+                if not question_dialog(self.gui, _('No editable formats'),
+                    _('Do you want to create an empty EPUB file to edit?')):
+                    return
+                tweakable_fmts = {'EPUB'}
+                self.gui.iactions['Add Books'].add_empty_format_to_book(book_id, 'EPUB')
+                current_idx = self.gui.library_view.currentIndex()
+                if current_idx.isValid():
+                    self.gui.library_view.model().current_changed(current_idx, current_idx)
+            else:
+                return error_dialog(self.gui, _('Cannot edit book'), _(
+                    'The book must be in the %s formats to edit.'
+                    '\n\nFirst convert the book to one of these formats.'
+                ) % (_(' or ').join(SUPPORTED)), show=True)
         from calibre.gui2.tweak_book import tprefs
         tprefs.refresh()  # In case they were changed in a Tweak Book process
         if len(tweakable_fmts) > 1: