scriptdialect

var Options = &syntax.FileOptions{
	Set:               true,
	While:             false,
	TopLevelControl:   true,
	GlobalReassign:    true,
	LoadBindsGlobally: false,
	Recursion:         false,
}

Options is the dialect every managed script is parsed and resolved under.

while and recursion are OFF. Both are unbounded control flow whose cost cannot be read off the source, and a script that needs either is doing computation that belongs in SQL. This is the deliberate restrictiveness of the feature, not an oversight, and it is the only pair of switches here that is about safety.

TopLevelControl and GlobalReassign are ON, and both defaults are inverted on purpose. Starlark's defaults come from Bazel, where a .bzl file is a DECLARATION loaded by other files: top-level control flow and rebinding a top-level name would make what a file declares depend on evaluation order. A managed script is the opposite — a procedure executed once, top to bottom, by one runner, loaded by nobody. Under the Bazel defaults an author could not write `total = 0` and then accumulate into it inside a loop without wrapping the whole script in a function, which is friction that buys no safety and no determinism: neither switch has anything to do with either. `load` stays file-local (and there is nothing to load).