breaking(v2): minimum required nodejs version 8.9->8.10 so we can use es2017

[endiliey]

Motivation

Node >= 8.10.0 support 100% ES2017 with native async await
while
Node 8.9.0 only support 100% ES6, 100% ES2016 and 73% ES2017.

Because of this, previously our TypeScript compiler always have to compile to ES6 and polyfill the await function.

For example, our generated js files for docusaurus/core/src/server/index is like this previously

var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
    return new (P || (P = Promise))(function (resolve, reject) {
        function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
        function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
        step((generator = generator.apply(thisArg, _arguments || [])).next());
    });
};
var __importDefault = (this && this.__importDefault) || function (mod) {
    return (mod && mod.__esModule) ? mod : { "default": mod };
};
Object.defineProperty(exports, "__esModule", { value: true });
const utils_1 = require("@docusaurus/utils");
const lodash_1 = __importDefault(require("lodash"));
const path_1 = __importDefault(require("path"));
const constants_1 = require("../constants");
const client_modules_1 = require("./client-modules");
const config_1 = require("./config");
const plugins_1 = require("./plugins");
const presets_1 = require("./presets");
const routes_1 = require("./routes");
const themes_1 = require("./themes");
function loadContext(siteDir) {
    const generatedFilesDir = path_1.default.resolve(siteDir, constants_1.GENERATED_FILES_DIR_NAME);
    const siteConfig = config_1.loadConfig(siteDir);
    const outDir = path_1.default.resolve(siteDir, constants_1.BUILD_DIR_NAME);
    const { baseUrl } = siteConfig;
    return {
        siteDir,
        generatedFilesDir,
        siteConfig,
        outDir,
        baseUrl,
    };
}
exports.loadContext = loadContext;
function loadPluginConfigs(context) {
    const { plugins: presetPlugins, themes: presetThemes } = presets_1.loadPresets(context);
    const { siteConfig } = context;
    return [
        ...presetPlugins,
        ...presetThemes,
        // Site config should the highest priority.
        ...(siteConfig.plugins || []),
        ...(siteConfig.themes || []),
    ];
}
exports.loadPluginConfigs = loadPluginConfigs;
function load(siteDir) {
    return __awaiter(this, void 0, void 0, function* () {
        // Context
        const context = loadContext(siteDir);
        const { generatedFilesDir, siteConfig, outDir, baseUrl } = context;
        const genSiteConfig = utils_1.generate(generatedFilesDir, constants_1.CONFIG_FILE_NAME, `export default ${JSON.stringify(siteConfig, null, 2)};`);
        // Plugins
        const pluginConfigs = loadPluginConfigs(context);
        const { plugins, pluginsRouteConfigs } = yield plugins_1.loadPlugins({
            pluginConfigs,
            context,
        });
        // Themes.
        const fallbackTheme = path_1.default.resolve(__dirname, '../client/theme-fallback');
        const pluginThemes = lodash_1.default.compact(plugins.map(plugin => plugin.getThemePath && plugin.getThemePath()));
        const userTheme = path_1.default.resolve(siteDir, constants_1.THEME_PATH);
        const alias = themes_1.loadThemeAlias([fallbackTheme, ...pluginThemes, userTheme]);
        // Make a fake plugin to resolve aliased theme components.
        plugins.push({
            name: 'docusaurus-bootstrap-plugin',
            configureWebpack: () => ({
                resolve: {
                    alias,
                },
            }),
        });
        // Load client modules.
        const clientModules = client_modules_1.loadClientModules(plugins);
        const genClientModules = utils_1.generate(generatedFilesDir, 'client-modules.js', `export default [\n${clientModules
            // import() is async so we use require() because client modules can have
            // CSS and the order matters for loading CSS.
            .map(module => `  require("${module}"),`)
            .join('\n')}\n];\n`);
        // Routing
        const { registry, routesChunkNames, routesConfig, routesPaths, } = yield routes_1.loadRoutes(pluginsRouteConfigs);
        const genRegistry = utils_1.generate(generatedFilesDir, 'registry.js', `export default {
${Object.keys(registry)
            .sort()
            .map(key => `  '${key}': [${registry[key].loader}, "${registry[key].modulePath}", require.resolveWeak("${registry[key].modulePath}")],`)
            .join('\n')}};\n`);
        const genRoutesChunkNames = utils_1.generate(generatedFilesDir, 'routesChunkNames.json', JSON.stringify(routesChunkNames, null, 2));
        const genRoutes = utils_1.generate(generatedFilesDir, 'routes.js', routesConfig);
        yield Promise.all([
            genClientModules,
            genSiteConfig,
            genRegistry,
            genRoutesChunkNames,
            genRoutes,
        ]);
        const props = {
            siteConfig,
            siteDir,
            outDir,
            baseUrl,
            generatedFilesDir,
            routesPaths,
            plugins,
        };
        return props;
    });
}
exports.load = load;

After compiling to ES2017, it can utilize node's own native async await which is more optimized

var __importDefault = (this && this.__importDefault) || function (mod) {
    return (mod && mod.__esModule) ? mod : { "default": mod };
};
Object.defineProperty(exports, "__esModule", { value: true });
const utils_1 = require("@docusaurus/utils");
const lodash_1 = __importDefault(require("lodash"));
const path_1 = __importDefault(require("path"));
const constants_1 = require("../constants");
const client_modules_1 = require("./client-modules");
const config_1 = require("./config");
const plugins_1 = require("./plugins");
const presets_1 = require("./presets");
const routes_1 = require("./routes");
const themes_1 = require("./themes");
function loadContext(siteDir) {
    const generatedFilesDir = path_1.default.resolve(siteDir, constants_1.GENERATED_FILES_DIR_NAME);
    const siteConfig = config_1.loadConfig(siteDir);
    const outDir = path_1.default.resolve(siteDir, constants_1.BUILD_DIR_NAME);
    const { baseUrl } = siteConfig;
    return {
        siteDir,
        generatedFilesDir,
        siteConfig,
        outDir,
        baseUrl,
    };
}
exports.loadContext = loadContext;
function loadPluginConfigs(context) {
    const { plugins: presetPlugins, themes: presetThemes } = presets_1.loadPresets(context);
    const { siteConfig } = context;
    return [
        ...presetPlugins,
        ...presetThemes,
        // Site config should the highest priority.
        ...(siteConfig.plugins || []),
        ...(siteConfig.themes || []),
    ];
}
exports.loadPluginConfigs = loadPluginConfigs;
async function load(siteDir) {
    // Context
    const context = loadContext(siteDir);
    const { generatedFilesDir, siteConfig, outDir, baseUrl } = context;
    const genSiteConfig = utils_1.generate(generatedFilesDir, constants_1.CONFIG_FILE_NAME, `export default ${JSON.stringify(siteConfig, null, 2)};`);
    // Plugins
    const pluginConfigs = loadPluginConfigs(context);
    const { plugins, pluginsRouteConfigs } = await plugins_1.loadPlugins({
        pluginConfigs,
        context,
    });
    // Themes.
    const fallbackTheme = path_1.default.resolve(__dirname, '../client/theme-fallback');
    const pluginThemes = lodash_1.default.compact(plugins.map(plugin => plugin.getThemePath && plugin.getThemePath()));
    const userTheme = path_1.default.resolve(siteDir, constants_1.THEME_PATH);
    const alias = themes_1.loadThemeAlias([fallbackTheme, ...pluginThemes, userTheme]);
    // Make a fake plugin to resolve aliased theme components.
    plugins.push({
        name: 'docusaurus-bootstrap-plugin',
        configureWebpack: () => ({
            resolve: {
                alias,
            },
        }),
    });
    // Load client modules.
    const clientModules = client_modules_1.loadClientModules(plugins);
    const genClientModules = utils_1.generate(generatedFilesDir, 'client-modules.js', `export default [\n${clientModules
        // import() is async so we use require() because client modules can have
        // CSS and the order matters for loading CSS.
        .map(module => `  require("${module}"),`)
        .join('\n')}\n];\n`);
    // Routing
    const { registry, routesChunkNames, routesConfig, routesPaths, } = await routes_1.loadRoutes(pluginsRouteConfigs);
    const genRegistry = utils_1.generate(generatedFilesDir, 'registry.js', `export default {
${Object.keys(registry)
        .sort()
        .map(key => `  '${key}': [${registry[key].loader}, "${registry[key].modulePath}", require.resolveWeak("${registry[key].modulePath}")],`)
        .join('\n')}};\n`);
    const genRoutesChunkNames = utils_1.generate(generatedFilesDir, 'routesChunkNames.json', JSON.stringify(routesChunkNames, null, 2));
    const genRoutes = utils_1.generate(generatedFilesDir, 'routes.js', routesConfig);
    await Promise.all([
        genClientModules,
        genSiteConfig,
        genRegistry,
        genRoutesChunkNames,
        genRoutes,
    ]);
    const props = {
        siteConfig,
        siteDir,
        outDir,
        baseUrl,
        generatedFilesDir,
        routesPaths,
        plugins,
    };
    return props;
}
exports.load = load;

Extra benefit is that our npm package should be lower in size due to removal of polyfills

Anyway, node 8.X is going for EOL this 31 December 2019. I think most people is in v10 or v12 anyway

Have you read the Contributing Guidelines on pull requests?

yes

Test Plan

• CI should all pass
• Netlify
• Local dev + hot reload ok

[docusaurus-bot]

Deploy preview for docusaurus-2 ready!

Built with commit bda7e74

https://deploy-preview-2045--docusaurus-2.netlify.com

[docusaurus-bot]

Deploy preview for docusaurus-preview ready!

Built with commit bda7e74

https://deploy-preview-2045--docusaurus-preview.netlify.com