Use a loop to evaluate binary comparisions to avoid recursion

[dylanahsmith]

Fixes #890

Problem

Running the following script results in a SystemStackError due to the recursive method calls used to evaluate conditions

require 'liquid'

code = "{% if true "
code << "and true " * 50_000
code << "%}rendered{% endif %}"
puts Liquid::Template.parse(code).render

Solution

Use a loop to evaluate the conditions, where local variables keep track of the current state, including a condition variable that is used instead of self to evaluate child conditions.

[fw42]

I guess it's a bit tricky to write a regression test for this?

[fw42]

This is smart, thanks Dylan! ❤️

[dylanahsmith]

The tricky part of writing the regression test would be determining the size of the condition chain needed to cause a SystemStackError with the recursive version of the code. Even after getting that right it would end up being a slow test in our test suite.

[ph3t]

👍