Fix for 6830. Generate a WorldCat link even if the only ISBN is an invalid ISBN 10

[scottbarnes]

Closes #6830

Fix

Technical

I am not sure it is the best approach, but a simple fix for the left-hand menu would be changing $:macros.WorldcatLink(isbn=isbn_13, oclc_numbers=oclc_numbers, referer=page.url(relative=False)) to $:macros.WorldcatLink(isbn=isbn_13 or isbn_10, oclc_numbers=oclc_numbers, referer=page.url(relative=False)).

If I understand correctly, the WorldCat link in the left-hand menu is rendered by openlibrary/macros/databarWork.html, and only displays if page.get_isbn13() returns something. This is so in part because of the following, from line 98, $:macros.WorldcatLink(isbn=isbn_13, oclc_numbers=oclc_numbers, referer=page.url(relative=False)).

I think databarWork.html is using only ISBN 13 because the page presupposes if there is an ISBN 10, then it will be converted to ISBN 13 when the page is created. This happens from the line 14 assignment of $ isbn_13 = page.get_isbn13(). If I understand correctly, get_isbn13() is from openlibrary/plugins/upstream/models.py. That function transforms ISBN 10 to ISBN 13, if there is an ISBN 10 and isn’t an ISBN 13. However, when the ISBN 10 is invalid, as the one in question is, the call to isbn_10_to_isbn13(isbn_10) returns None:

def get_isbn13(self):
    """Fetches either isbn_13 or isbn_10 from record and returns canonical
    isbn_13
    """
    isbn_13 = self.isbn_13 and canonical(self.isbn_13[0])
    if not isbn_13:
        isbn_10 = self.isbn_10 and self.isbn_10[0]
        return isbn_10 and isbn_10_to_isbn_13(isbn_10)
   return isbn_13

Without an ISBN 13, and without a valid ISBN 10 that can convert to ISBN 13, I think the WorldCat link won’t show. Hence the suggestion to make the above one line change, which falls back to the ISBN 10 directly.

Some things I tested, prior to making the change. Starting with no ISBN present (on the edit page):

1. add an invalid ISBN 10 and save: no WorldCat link;
2. add an invalid ISBN 10, save, and then add a a valid ISBN 10, save: no WorldCat link;
3. add a valid ISBN 10 and and a invalid ISBN 10 and then save: yes, there is a WorldCat link; and
4. add a invalid ISBN 10 and and a valid ISBN 10 and then save: no, there is not a WorldCat link.

This may be because get_isbn13() is only checking index 0 of self.isbn_10. So another fix might be to run isbn_10_to_isbn_13() on every ISBN listed, though I haven’t looked into this, in part because that wouldn’t fix this specific issue, as there is just one ISBN 10 here, and it’s invalid and won't convert to ISBN 13.

With the above change, each of the things I tried links to WorldCat, and the WorldCat link to the invalid ISBN 10 also works, at least for this book. However, if an invalid ISBN 10 is added first, and then a valid ISBN 10 is added later, with this change the WorldCat link will be to the invalid ISBN 10 rather than the valid one being used (and thereby converted to ISBN 13). If an ISBN 13 is added, that is used instead.

Edit 3: the edit to openlibrary/templates/books/edition-sort.html is a bit easier to explain, based on the above. It too was querying only ISBN 13, via get_isbn13(), which converts ISBN 10 to ISBN 13 if there is an ISBN 10 and there is no ISBN 13, but again, that won't work with this invalid ISBN 10.

There may be a reason for always using ISBN 13 and I want to make sure that using ISBN 10 in places instead of ISBN 13 won't break things.

Testing

Try adding a book with just the invalid ISBN 10 in question: 7204051613. The link to WorldCat at https://worldcat.org/isbn/7204051613 should work. If a valid ISBN 13 is added, that should take precedence.

Screenshot

With the proposed PR:

Without the proposed PR (https://openlibrary.org/books/OL39212557M/Shou_xiang_bang_jia_an_Meng_mian_nu_ren):

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