@slimlib/smart-mock

Smart Mock

Yet another proxy mock (YAPM?). Still in a very early state (EXPECT BUGS!).

Mock that records operations for code generation later. Idea is somewhat similar to prepack but instead of interpreting code by other JS code we run it in JS VM and later use mock to repeat the same operations. Ideally combined with a terser like optimizer. Please check the example in pkgbld how it is used to eject config.

Changelog

API

default () => { createMock, generateGlobals, generate }

Default export function is a factory that creates 3 other functions with shared state.

createMock<T extends object>(object: T, name: string): T

Function to create mock wrapper around object and defining global name for later usage. object can be a real original object or a pure mock object with the same behavior for the specific situation. All operations on this object will be recorded by mock.

generate(object: unknown): string

Function to generate code for some export point (exit point). It will try to automatically inline operations that can be inlined.

generateGlobals(): string

Function to generate global code that cannot be inlined to exit point.

Example

import createMockProvider from '@slimlib/smart-mock';
const { createMock, generate, generateGlobals } = createMockProvider();
const mock = createMock({
    fly() { return { status: 'flying' }; },
    land() {},
    name: ''
}, 'fly');
mock.name = 'Moth';
const status = mock.fly();
mock.land();

At this point generate(mock) will result in mock, generate(mock.name) in 'Moth' and generate(status) in fly.fly(). And if you afterwards call generateGlobals() you get something like:

fly.name = "Moth"
const tmp_0 = fly.land
tmp_0()

Each generate call updates counters / flags in mock so generateGlobals only emits what was not generated at the time of call.

License

MIT