Add by ISBN: Allow adding using identifiers other than ISBN as well. Fixes #2003227 [enhancement request regarding add from isbn](https://bugs.launchpad.net/calibre/+bug/2003227)

src/calibre/gui2/actions/add.py

@@ -371,14 +371,26 @@ class AddAction(InterfaceAction):
         existing_isbns.pop('', None)
         ok = []
         duplicates = []
+        checker_maps = {}
         for book in books:
-            q = normalize_isbn(book['isbn'])
+            if 'isbn' in book:
-            if q and q in existing_isbns:
+                q = normalize_isbn(book['isbn'])
-                duplicates.append((book, existing_isbns[q]))
+                if q and q in existing_isbns:
+                    duplicates.append((book, existing_isbns[q]))
+                else:
+                    ok.append(book)
             else:
-                ok.append(book)
+                key = book['']
+                if key not in checker_maps:
+                    checker_maps[key] = {ids.get(key, ''): book_id for book_id, ids in book_id_identifiers.items()}
+                    checker_maps[key].pop('', None)
+                q = book[key]
+                if q in checker_maps[key]:
+                    duplicates.append((book, checker_maps[key][q]))
+                else:
+                    ok.append(book)
         if duplicates:
-            det_msg = '\n'.join(f'{book["isbn"]}: {db.field_for("title", book_id)}' for book, book_id in duplicates)
+            det_msg = '\n'.join(f'{book[book[""]]}: {db.field_for("title", book_id)}' for book, book_id in duplicates)
             if question_dialog(self.gui, _('Duplicates found'), _(
                 'Books with some of the specified ISBNs already exist in the calibre library.'
                 ' Click "Show details" for the full list. Do you want to add them anyway?'), det_msg=det_msg
@@ -416,7 +428,10 @@ class AddAction(InterfaceAction):
                 return
 
             mi = MetaInformation(None)
-            mi.isbn = x['isbn']
+            if x[''] == 'isbn':
+                mi.isbn = x['isbn']
+            else:
+                mi.set_identifiers({x['']:x[x['']]})
             if self.isbn_add_tags:
                 mi.tags = list(self.isbn_add_tags)
             fmts = [] if x['path'] is None else [x['path']]

src/calibre/gui2/dialogs/add_from_isbn.py

@@ -55,7 +55,11 @@ class AddFromISBN(QDialog):
             "<p>Any invalid ISBNs in the list will be ignored.</p>\n"
             "<p>You can also specify a file that will be added with each ISBN. To do this enter the full"
             " path to the file after a <code>&gt;&gt;</code>. For example:</p>\n"
-            "<p><code>9788842915232 &gt;&gt; %s</code></p>"), self)
+            "<p><code>9788842915232 &gt;&gt; %s</code></p>"
+            "<p>To use identifiers other than ISBN use key:value syntax, For example:</p>\n"
+            "<p><code>amazon:B001JK9C72</code></p>"
+        ), self)
+
         l.addWidget(la), la.setWordWrap(True)
         l.addSpacing(20)
         self.la2 = la = QLabel(_("&Tags to set on created book entries:"), self)
@@ -100,18 +104,26 @@ class AddFromISBN(QDialog):
             parts = [x.strip() for x in parts]
             if not parts[0]:
                 continue
-            isbn = check_isbn(parts[0])
+            if ':' in parts[0]:
-            if isbn is not None:
+                prefix, val = parts[0].partition(':')[::2]
-                isbn = isbn.upper()
-                if isbn not in self.isbns:
-                    self.isbns.append(isbn)
-                    book = {'isbn': isbn, 'path': None}
-                    if len(parts) > 1 and parts[1] and \
-                        os.access(parts[1], os.R_OK) and os.path.isfile(parts[1]):
-                        book['path'] = parts[1]
-                    self.books.append(book)
             else:
-                bad.add(parts[0])
+                prefix, val = 'isbn', parts[0]
+            path = None
+            if len(parts) > 1 and parts[1] and os.access(parts[1], os.R_OK) and os.path.isfile(parts[1]):
+                path = parts[1]
+
+            if prefix == 'isbn':
+                isbn = check_isbn(parts[0])
+                if isbn is not None:
+                    isbn = isbn.upper()
+                    if isbn not in self.isbns:
+                        self.isbns.append(isbn)
+                        self.books.append({'isbn': isbn, 'path': path, '': 'isbn'})
+                else:
+                    bad.add(parts[0])
+            else:
+                if prefix != 'path':
+                    self.books.append({prefix: val, 'path': path, '':prefix})
         if bad:
             if self.books:
                 if not question_dialog(self, _('Some invalid ISBNs'),