• implement expression evaluation
• add new "Evalute Expression" node
• Replace existing placeholder engine with expressions
• Refactor internal type system to align with expressions
• Implement all previous placeholders as expressions
• Update documentation
• Measure and evaluate performance effects (seems negligible)

Open Questions

• Function calls vs maps (e.g. arg("myarg.result") vs args.myarg.result vs args["myarg"].result)
• Eliminate FlowValue completely? Make variable values pure JSON without additional type annotation? (moved to Refactor internal type system #62)
  • We use them in flows to store the result of a node and make it accessible to others
  • We use them in variables values to store stuff with a type annoation
  • In expressions, they become a pain in the ass because a FlowValueInt can't be used like a normal int
  • When incrementing the result of a previous node we have this: int(result) -> FlowValueInt(result) -> {{int(result) + 1}} -> FlowValueInt(result)
  • By eliminating the conversion between a regular int and FlowValueInt we could simplify this a lot
  • We lose the ability to validate types of values
• Supporting complex expressions everywhere ✅

part of #53
closes #55