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Diffstat (limited to '')
-rw-r--r-- | devtools/client/performance-new/shared/typescript-lazy-load.jsm.js | 55 |
1 files changed, 55 insertions, 0 deletions
diff --git a/devtools/client/performance-new/shared/typescript-lazy-load.jsm.js b/devtools/client/performance-new/shared/typescript-lazy-load.jsm.js new file mode 100644 index 0000000000..c640572c53 --- /dev/null +++ b/devtools/client/performance-new/shared/typescript-lazy-load.jsm.js @@ -0,0 +1,55 @@ +/* This Source Code Form is subject to the terms of the Mozilla Public + * License, v. 2.0. If a copy of the MPL was not distributed with this + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ +// @ts-check +"use strict"; + +/** + * TypeScript can't understand the lazyRequireGetter mechanism, due to how it defines + * properties as a getter. This function, instead provides lazy loading in a + * TypeScript-friendly manner. It applies the lazy load memoization to each property + * of the provided object. + * + * Example usage: + * + * const lazy = createLazyLoaders({ + * moduleA: () => require("module/a"), + * moduleB: () => require("module/b"), + * }); + * + * Later: + * + * const moduleA = lazy.moduleA(); + * const { objectInModuleB } = lazy.moduleB(); + * + * @template T + * @param {T} definition - An object where each property has a function that loads a module. + * @returns {T} - The load memoized version of T. + */ +function createLazyLoaders(definition) { + /** @type {any} */ + const result = {}; + for (const [key, callback] of Object.entries(definition)) { + /** @type {any} */ + let cache; + result[key] = () => { + if (cache === undefined) { + cache = callback(); + } + return cache; + }; + } + return result; +} + +// Provide an exports object for the JSM to be properly read by TypeScript. +/** @type {any} */ +var module = {}; + +module.exports = { + createLazyLoaders, +}; + +// Object.keys() confuses the linting which expects a static array expression. +// eslint-disable-next-line +var EXPORTED_SYMBOLS = Object.keys(module.exports); |