element-vir/dist/declarative-element/directives/render-async.directive.js

Heroic. Reactive. Declarative. Type safe. Web components without compromise.

import { check } from '@augment-vir/assert';
import { extractErrorMessage } from '@augment-vir/common';
/**
 * Given a {@link AsyncProp} instance, call and return the output of the `resolutionRender` parameter
 * once the {@link AsyncProp} has been resolved, call and return the output of the `errorRender`
 * parameter if the {@link AsyncProp} errored out, return the `fallback` parameter in all other
 * cases.
 *
 * This is the full function definition and implementation.
 *
 * @category Async
 */
// eslint-disable-next-line @virmator/prefer-params-object
export function renderAsync(asyncProp, 
/** This value will be rendered if the async prop has not settled yet. */
fallback, resolutionRender, errorRender, options = {}) {
    const asyncPropValue = options.useLastResolvedValue
        ? asyncProp.lastResolvedValue
        : asyncProp.value;
    if (asyncPropValue instanceof Error) {
        const errorResult = errorRender
            ? errorRender(asyncPropValue)
            : extractErrorMessage(asyncPropValue);
        return errorResult;
    }
    else if (check.isPromiseLike(asyncPropValue) ||
        /**
         * `lastResolvedValue` is `undefined` both before the first resolution and when the value
         * genuinely resolved to `undefined`. Only the former is a loading state, so a still-pending
         * `value` is what distinguishes them.
         */
        (options.useLastResolvedValue &&
            asyncPropValue === undefined &&
            check.isPromiseLike(asyncProp.value))) {
        const fallbackResult = fallback;
        return fallbackResult;
    }
    else {
        const resolutionResult = resolutionRender
            ? resolutionRender(asyncPropValue)
            : asyncPropValue;
        return resolutionResult;
    }
}