@web/dev-server-core/dist/middleware/pluginTransformMiddleware.js

Web dev server core

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.pluginTransformMiddleware = void 0;
const PluginTransformCache_js_1 = require("./PluginTransformCache.js");
const utils_js_1 = require("../utils.js");
/**
 * Sets up a middleware which allows plugins to transform files before they are served to the browser.
 */
function pluginTransformMiddleware(logger, config, fileWatcher) {
    var _a;
    const cache = new PluginTransformCache_js_1.PluginTransformCache(fileWatcher, config.rootDir);
    const transformPlugins = ((_a = config.plugins) !== null && _a !== void 0 ? _a : []).filter(p => 'transform' in p);
    if (transformPlugins.length === 0) {
        // nothing to transform
        return (ctx, next) => next();
    }
    return async (context, next) => {
        var _a;
        // The cache key is the request URL plus any specific cache keys provided by plugins.
        // For example plugins might do different transformations based on user agent.
        const cacheKey = context.url +
            (await Promise.all(transformPlugins.map(p => { var _a; return (_a = p.transformCacheKey) === null || _a === void 0 ? void 0 : _a.call(p, context); })))
                .filter(_ => _)
                .join('_');
        const result = await cache.get(cacheKey);
        if (result) {
            context.body = result.body;
            for (const [k, v] of Object.entries(result.headers)) {
                context.response.set(k, v);
            }
            logger.debug(`Serving cache key "${cacheKey}" from plugin transform cache`);
            return;
        }
        await next();
        if (context.status < 200 || context.status >= 300) {
            return;
        }
        try {
            // ensure response body is turned into a string or buffer
            await (0, utils_js_1.getResponseBody)(context);
            let disableCache = false;
            let transformedCode = false;
            for (const plugin of transformPlugins) {
                const result = await ((_a = plugin.transform) === null || _a === void 0 ? void 0 : _a.call(plugin, context));
                if (typeof result === 'object') {
                    disableCache = result.transformCache === false ? true : disableCache;
                    if (result.body != null) {
                        context.body = result.body;
                        transformedCode = true;
                        logger.debug(`Plugin ${plugin.name} transformed ${context.path}.`);
                    }
                    if (result.headers) {
                        for (const [k, v] of Object.entries(result.headers)) {
                            context.response.set(k, v);
                        }
                    }
                }
                else if (typeof result === 'string') {
                    context.body = result;
                    transformedCode = true;
                    logger.debug(`Plugin ${plugin.name} transformed ${context.path}.`);
                }
            }
            if (transformedCode && !disableCache) {
                logger.debug(`Added cache key "${cacheKey}" to plugin transform cache`);
                const filePath = (0, utils_js_1.getRequestFilePath)(context.url, config.rootDir);
                cache.set(filePath, context.body, context.response.headers, cacheKey);
            }
        }
        catch (e) {
            if (e instanceof utils_js_1.RequestCancelledError) {
                return undefined;
            }
            context.body = 'Error while transforming file. See the terminal for more information.';
            context.status = 500;
            const error = e;
            if (error.name === 'PluginSyntaxError') {
                logger.logSyntaxError(error);
                return;
            }
            if (error.name === 'PluginError') {
                logger.error(error.message);
                return;
            }
            throw error;
        }
    };
}
exports.pluginTransformMiddleware = pluginTransformMiddleware;
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