express-transform-bare-module-specifiers/dist/compile-middleware.js

Express middleware to transform bare module specifiers on-the-fly.

"use strict";
/**
 * Based entirely on:
 * https://github.com/Polymer/tools/blob/e731b880a0d94a551f5781111f2f9c81cb64c642/packages/polyserve/src/compile-middleware.ts
 */
Object.defineProperty(exports, "__esModule", { value: true });
const content_type_1 = require("content-type");
const LRU = require("lru-cache");
const path = require("path");
const babel = require("@babel/core");
const transform_middleware_1 = require("./transform-middleware");
const javaScriptMimeTypes = [
    'application/javascript',
    'application/ecmascript',
    'text/javascript',
    'text/ecmascript'
];
const compileMimeTypes = [...javaScriptMimeTypes];
function getContentType(response) {
    const contentTypeHeader = response.get('Content-Type');
    return contentTypeHeader && content_type_1.parse(contentTypeHeader).type;
}
exports.babelCompileCache = LRU({
    length: (n, key) => n.length + key.length,
    max: 52428800
});
// TODO(justinfagnani): see if we can just use the request path as the key
// See https://github.com/Polymer/polyserve/issues/248
exports.getCompileCacheKey = (requestPath, body) => requestPath + body;
function babelCompile({ rootDir = process.cwd(), modulesUrl = '/node_modules' } = {}) {
    return transform_middleware_1.transformResponse({
        shouldTransform(request, response) {
            if ('nocompile' in request.query) {
                return false;
            }
            if (!compileMimeTypes.includes(getContentType(response))) {
                return false;
            }
            return true;
        },
        transform(request, response, body) {
            const cacheKey = exports.getCompileCacheKey(request.baseUrl + request.path, body);
            const cached = exports.babelCompileCache.get(cacheKey);
            if (cached !== undefined) {
                return cached;
            }
            const contentType = getContentType(response);
            let transformed = body;
            if (javaScriptMimeTypes.includes(contentType)) {
                const result = babel.transformSync(body, {
                    filename: path.resolve(rootDir, request.path.replace(/^\//, '')),
                    plugins: [
                        ['bare-import-rewrite', {
                                modulesDir: modulesUrl,
                                rootBaseDir: rootDir
                            }]
                    ],
                    sourceMaps: 'inline'
                });
                if (result && result.code) {
                    transformed = result.code;
                }
            }
            exports.babelCompileCache.set(cacheKey, transformed);
            return transformed;
        }
    });
}
exports.babelCompile = babelCompile;
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