#22232: Template extends tag can cause recursion
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Reporter: galedragon | Owner: Saidin7979
Type: Bug | Status: assigned
Component: Template system | Version: 1.6
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 1 | UI/UX: 0
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Comment (by russellm):
Hrm. This is an interesting problem. On the one hand, it would be nice to
raise a humane error message, but if it's only going to catch the one-
level recursion case, I'm starting to wonder if it's worth the effort.
Adding a potentially expensive check to the top of every template load so
that you can present a nicer error message in the edge case of recursive
templates seems like too high a price to pay.
If we can't find an efficient way to catch the complex circular case, I'm
inclined to turn this into a documentation fix (ie. noting in the
discussion around extends that circular loops may cause stack overflow
errors).
One option might be to handle this at render time, rather than at load
time. If you put something in the context that tracks which templates have
been used, and you try to re-use a template name, that indicates a
circular loop, and you can raise an error. This should be relatively cheap
(a set lookup & insertion on each new template file used); as long as we
can find a clean place to track the data, it might suffice as a solution.
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Ticket URL: <https://code.djangoproject.com/ticket/22232#comment:4>
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