[reportlab-users] IndexError exception in platypus.paraparser

[Germán M. Bravo]

Please do consider changing this bit (at least I have not been having any
more problems after this patch)

On Thu, Dec 31, 2015 at 11:32 AM, Germán M. Bravo <german.mb at gmail.com>
wrote:

> This definitely fixes the IndexError exception I've been getting.
>
> I applied this monkey patch to fix it:
>
> # FIXME: This monkeypatches rml2pdf.TTParagraphMixin so _parser is no
> longer
> # a shared instance of TTParser class defined as a class property
> rml2pdf.TTParagraphMixin._parser = property(lambda self: setattr(self,
> '__parser', self.__dict__.get('__parser') or rml2pdf.TTParser()) or
> self.__parser)
>
>
> On Thu, Dec 31, 2015 at 1:35 AM, Germán M. Bravo <german.mb at gmail.com>
> wrote:
>
>> I'm working with ReportLab in a threaded environment and I've been
>> getting a weird exception about IndexError when doing some operations such
>> as _pop() during platypus.paraparser.ParaParser.end_br(). I think I've
>> tracked the error down the fact _stack is a member of the TTParser instance
>> (using rml2pdf).
>>
>> After googling around, I found a place where the source code of rml2pdf
>> shows this:
>>
>> class TTParagraphMixin:
>>     _CLEAN_SPACE = 0
>>     _parser = TTParser()
>>     ...
>>
>> Then, doing:
>>
>> from rlextra.rml2pdf import rml2pdf
>> print(repr(rml2pdf.TTParagraphMixin._parser))
>>
>> confirms TTParser is an instance: <rlextra.rml2pdf.rml2pdf.TTParser
>> instance at 0x1053eae18>
>>
>> This means TTParser instance there is an instance placed as a property of
>> TTParagraphMixin at class level (which means it's shared by all instances
>> of TTParagraph, TTXPreformatted and others) ...but (at least)
>> TTParser._stack could be modified by several threads at the same time
>> (causing the aforesaid exception to raise from time to time).
>>
>>
>
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