polymer-build
Version:
A library of Gulp build tasks
70 lines • 3.19 kB
JavaScript
;
/**
* @license
* Copyright (c) 2018 The Polymer Project Authors. All rights reserved.
* This code may only be used under the BSD style license found at
* http://polymer.github.io/LICENSE.txt
* The complete set of authors may be found at
* http://polymer.github.io/AUTHORS.txt
* The complete set of contributors may be found at
* http://polymer.github.io/CONTRIBUTORS.txt
* Code distributed by Google as part of the polymer project is also
* subject to an additional IP rights grant found at
* http://polymer.github.io/PATENTS.txt
*/
Object.defineProperty(exports, "__esModule", { value: true });
const plugin_syntax_dynamic_import_1 = require("@babel/plugin-syntax-dynamic-import");
const template_1 = require("@babel/template");
const ast = template_1.default.ast;
/**
* Rewrites dynamic import() calls to AMD async require() calls.
*/
exports.dynamicImportAmd = {
inherits: plugin_syntax_dynamic_import_1.default,
visitor: {
Program(path) {
// We transform dynamic import() into a Promise whose initializer calls
// require(). We must use the "local" require - the one provided by the
// AMD loaded when a module explicitly depends on the "require" module ID.
// To get the emitted define() call to depend on "require", we inject an
// import of a module called "require".
// Collect all the NodePaths to dynamic import() expressions
// and all the identifiers in scope for them.
const identifiers = new Set();
const dynamicImports = [];
path.traverse({
CallExpression(path) {
if (path.node.callee.type === 'Import') {
dynamicImports.push(path);
const bindings = path.scope.getAllBindings();
for (const name of Object.keys(bindings)) {
identifiers.add(name);
}
}
}
});
if (dynamicImports.length === 0) {
return;
}
// Choose a unique name to import "require" as.
let requireId = undefined;
do {
requireId = path.scope.generateUidIdentifier('require');
} while (identifiers.has(requireId.name));
// Inject the import of "require"
const statements = path.node.body;
statements.unshift(ast `import * as ${requireId} from 'require';`);
// Transform the dynamic import callsites
for (const importPath of dynamicImports) {
const specifier = importPath.node.arguments[0];
// Call as `require.default` because the AMD transformer that we assume
// is running next will rewrite `require` from a function to a module
// object with the function at `default`.
importPath.replaceWith(ast `(
new Promise((res, rej) => ${requireId}.default([${specifier}], res, rej))
)`);
}
},
},
};
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