@lwc/features

Features

RFC

Compile-time flags

Runtime flags

Runtime flags can be enabled or disabled by setting a boolean value for that flag in globalThis.LWC_config.features. If the flag is not explicitly configured, the feature is disabled by default. This configuration object must appear before @lwc/engine is initialized and should be defined at the application layer.

Limitations

Must be all uppercase

// Does not work
if (enableFoo) {
    ...
}

// Does work
if (ENABLE_FOO) {
    ...
}

Only works with if-statements

// Does not work
const foo = ENABLE_FOO ? 1 : 2;

// Does work
let foo;
if (ENABLE_FOO) {
    foo = 1;
} else {
    foo = 2;
}

Only works with identifiers

// Does not work
if (isTrue(ENABLE_AWESOME_FEATURE)) {
    // awesome feature
}

// Does work
if (ENABLE_AWESOME_FEATURE) {
    // awesome feature
}

Initialization code cannot be tested

Toggling the value of ENABLE_FOO during a test will not change the return value of getFooValue.

import { ENABLE_FOO } from '@lwc/features';

let foo;
if (ENABLE_FOO) {
    foo = 1;
} else {
    foo = 2;
}

function getFooValue() {
    return foo;
}