Incorrect highlighting when using new-style string formatting and a % sign. #7

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1. 1st1 commented on Oct 20, 2015

   

   1st1

   on Oct 20, 2015

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   This is because "% s" % 123 and %o are valid in Python -- so we highlight both new and old formatting...
2. fpierfed commented on Oct 20, 2015

   

   fpierfed

   on Oct 20, 2015

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   I agree that it is a tricky situation. In the example above, however, it seems to me that the correct behavior would have been to highlight {:.02f} only and leave % o alone. Discriminating this in code would require looking at the whole line and seeing that we have a call to .format without a % operator...
3. 1st1

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   enhancement

   on Oct 20, 2015
4. vpetrovykh commented on Oct 20, 2015

   

   vpetrovykh

   on Oct 20, 2015

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   Looking at the whole line is not a viable strategy. In principle, you're never guaranteed that .format will even be on the same line, so it requires an infinite lookahead, which cannot be implemented. Having inconsistent highlighting based on the presence of .format on the same line is also undesirable (not to mention tricky due to quoting, escaping and comments potentially having .format in them). There is also a fair amount of code where .format does not appear on the same line as the string at all (example taken from here):

   msg = '{arg!r} parameter is positional only, ' \
         'but was passed as a keyword'
   msg = msg.format(arg=param.name)
   raise TypeError(msg) from None
   

   Since we cannot reliably tell which formatting is actually going to be used, we highlight both kinds to help spot issues like this:

   >>> '% of the time "{token}" has been seen: % 10d' % 42
   Traceback (most recent call last):
     File "<stdin>", line 1, in <module>
   TypeError: not enough arguments for format string
   
5. vpetrovykh

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   wontfix

   and removed

   enhancement

   on Oct 20, 2015
6. vpetrovykh

   closed this as completedon Oct 20, 2015
7. 1st1 commented on Oct 20, 2015

   

   1st1

   on Oct 20, 2015

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   (see also 11342d4)