Split this from issue 1581476 as suggested
 by Guilherme Polo (gpolo).

>Matthias: your issue about the pattern should be placed in a 
>different
>issue.

Quote of my original report:
(This is about the search function of the Text class in Tkinter.
 An IndexError is raised when pattern == '')
...
>In addition I get an IndexError, if I delete the
>last character of the search string.
>Does Tk allow calling search with an empty pattern?

>Tkinter could handle this (with a correct result)
>with the following change in Tkinter.py / Text.search():

>if pattern[0] == '-': args.append('--')
>->
>if pattern and pattern[0] == '-': args.append('--')

A further remark from Guilherme Polo (gpolo):

>For the suggestion about fixing the search method regarding the 
>pattern:
>the fix is almost fine, but we need to disallow None as a pattern.

I do not understand that remark. Is it to avoid the TclError?
Or because the exception changes (IndexError -> TclError)?
What do you want to do when pattern == None? Raise ValueError
or IndexError (as before)?

Appended slightly simplified demo program from issue 1581476
and a patch against trunk r68445.

Cheers,
Matthias Kievernagel
mkiever/at/web/dot/de

I don't know what I was thinking when I said that, the check you are
doing in the patch is fine. And just to answer your next question: it
would raise ValueError.

Also, it would be good to add the other missing search switches.

Fixed on r69461, r69462, r69463 and r69464, thanks.

Will be adding tests for Tkinter.Text.search for trunk and py3k only.

I've added some tests for it on r69467 now.