The static scopes of Jinja2, from its idtracking module.
Jinja2 compiles each scope of a template to the local variables of a Python function: the root of the template, a block, a macro, a caller, the body of a loop, a with block and others. At the start of a scope, each name that the scope sets before it reads it starts as missing, also when the render has a variable with that name. A loop that reads x before a later top-level {% set x = 1 %} sees x as undefined. At the end of a scope that is not a function, such as a loop, its names become missing again, which a macro that the scope defined can see.
annotate/1 analyzes the scopes of a syntax tree like Jinja2, and gives each node that opens a scope its t/0. The evaluator applies them.
Summary
Types
unset lists the names that are missing at the start of the scope. exit gives the value of each name of the scope after the scope ends: :missing for a parameter, such as the target of a loop, which prints as missing, and :unset for the others, which are undefined.
Functions
Returns the syntax tree with the scope of each node that opens one, and the scope of the root.
Types
@type t() :: %{ unset: [String.t()], exit: %{required(String.t()) => :missing | :unset}, self: boolean(), super: boolean(), captured: boolean() }
unset lists the names that are missing at the start of the scope. exit gives the value of each name of the scope after the scope ends: :missing for a parameter, such as the target of a loop, which prints as missing, and :unset for the others, which are undefined.
self is true when the root of a template or a block reads self, and super when a block reads super, which Jinja2 then sets at the start of the scope. captured is true when the scope defines a macro or a call block, which can read the scope after it ends.