Reproducible builds are all the craze right now (exhibit a: https://reproducible-builds.org/). The basic premise is: code generation, compilation, heck, builds in general should behave deterministically, meaning: given the same set of inputs return the same output.

The main pain point with Symfony comes from the cache warmup process. console cache:warmup
will return a different results on two consecutive builds. The three main problem areas I've found so far:

• Container IDs are randomly generated
• Names and symbols of lazy proxies are randomly generated
• Compiled twig templates are randomly generated

Before we start digging deeper into this, first question: is that something Symfony wants to properly support or is that something that should somehow live outside of Symfony?

Demo project