Accessing private members

Titanoboa allows access to private members of a contract. This is useful for testing internal functions or variables without having to expose them to the outside world.

Given a vyper module foo.vy in the same folder as your python code:

x: uint256
y: immutable(uint256)

def __init__(y_initial: uint256):
    self.x = 42
    self.y = y_initial

@internal
@pure
def _bar() -> uint256:
    return 111

We can notice that x, y and _bar are all private members of the contract that wouldn't be easily accessible in a normal context. Boa allows access to all of these members, let's see how.

Accessing internal functions

internal functions can be accessed by calling the function from the internal attribute of the contract.

import foo

my_contract = foo(1234)

my_contract.internal._bar() # returns 111

Accessing private storage variables

Private storage variables can be accessed by calling the variable from the _storage attribute of the contract:

import foo

my_contract = foo(1234)

my_contract._storage.x.get() # returns 42

Accessing private immutable variables

Similarly private immutable variables can be accessed by calling the variable from the _immutable attribute of the contract:

import foo

my_contract = foo(1234)

my_contract._immutables.y # returns 1234

Accessing internal module variables

Since vyper 0.4.0 it is possible to modularize contracts.

Boa doesn't yet support accessing private module variables. However this can easily be done using eval.

Given a module bar.vy:

# bar.vy
x: uint256

If another contract foo.vy imports bar:

# foo.vy
import bar

foo: public(uint256)

It is possible to access bar.x from foo using eval:

foo = boa.load("foo.vy")

foo.eval("bar.x") # returns the value of bar.x