Fix extra helper introduced with multiple async dependencies (#34)

Author: steverep

package.json

@@ -44,7 +44,8 @@
     "format": "prettier --cache --write .",
     "build": "tsc --build --verbose",
     "test": "mocha --config mocha.config.cjs",
-    "clean": "tsc --build --clean && rm -rf test/dist",
+    "snapshot": "CHAI_JEST_SNAPSHOT_UPDATE_ALL=true yarn run test",
+    "clean": "tsc --build --clean && rm -rf dist test/dist",
     "prepublish": "yarn run lint",
     "prepack": "yarn run build",
     "postpack": "yarn run clean"

src/babel-plugin-runtime-dependency.cts

@@ -36,17 +36,17 @@ export const runtimeDependencyPlugin = (): PluginObj<ThisPluginPass> => ({
         );
       }
       const localID = path.node.specifiers[0].local.name;
+      const source = path.node.source.value;
       // In record mode, just save the request and exit.
       if (this.opts.record) {
-        const dependencyID = ID_PREFIX + localID;
-        this.opts.map.set(path.node.source.value, dependencyID);
+        this.opts.map.set(source, ID_PREFIX + localID);
         return;
       }
       // Find the identifier that Webpack injected for this source.
-      const dependencyID = this.opts.map.get(path.node.source.value);
+      const dependencyID = this.opts.map.get(source);
       if (!dependencyID) {
         throw Error(
-          `Encountered a dependency that was not recorded:\n${path.getSource()}`,
+          `Encountered a dependency that was not recorded: ${source}`,
         );
       }
       // Check that the dependency was declared at the top scope, rename it,

src/index.cts

@@ -41,6 +41,11 @@ const BABEL_DEFAULTS: Readonly<BabelOptions> = {
   compact: false,
   sourceMaps: true,
   presets: ["@babel/preset-env"],
+  // A destructured assignment added by Webpack is also transpiled, which we can
+  // safely assume is an array.  Otherwise, Babel will introduce an extra
+  // unrecorded helper whenever an async module has multiple async dependencies.
+  // https://github.com/webpack/webpack/blob/be1d35eb02bbedb05ca6ac846fec38a563dcd47f/lib/async-modules/AwaitDependenciesInitFragment.js#L64-L69
+  assumptions: { iterableIsArray: true },
 };
 
 export class TransformAsyncModulesPlugin implements WebpackPluginInstance {

test/goodbye.spec.ts

@@ -12,8 +12,8 @@ const require = createRequire(import.meta.url);
 const { devDependencies } =
   require("../package.json") as typeof import("../package.json");
 const context = fileURLToPath(new URL(".", import.meta.url));
-const ENTRY_NAMES = ["simple", "chained"] as const;
-const CHUNK_CHECKS = { goodbye: 1, parent: 2 } as const;
+const ENTRY_NAMES = ["simple", "chained", "multiple"] as const;
+const CHUNK_CHECKS = { goodbye: 1, parent: 2, with2: 3 } as const;
 
 const numMatchesTest = (file: string, pattern: RegExp, nMatches: number) =>
   async function () {

test/goodbye.spec.ts.snap

@@ -5,17 +5,25 @@ exports[`Goodbye delay with node 0.12 target Compiles with correct debug log 1`]
     Transforming module ./src/goodbye.js for chunk src_goodbye_js
     Transforming module ./src/goodbye.js for chunk src_parent_js
     Transforming module ./src/parent.js for chunk src_parent_js
+    Transforming module ./src/another.js for chunk src_with2_js
+    Transforming module ./src/goodbye.js for chunk src_with2_js
+    Transforming module ./src/with2.js for chunk src_with2_js
 
 goodbye-v0.12 compiled successfully"
 `;
 
 exports[`Goodbye delay with node 0.12 target using runtime Compiles with correct debug log 1`] = `
 "DEBUG LOG from TransformAsyncModulesPlugin
     Adding dependencies for top level await parsed in ./src/goodbye.js
+    Adding dependencies for top level await parsed in ./src/another.js
     Adding and reprocessing dependencies for ./src/parent.js
+    Adding and reprocessing dependencies for ./src/with2.js
     Transforming module ./src/goodbye.js for chunk src_goodbye_js
     Transforming module ./src/goodbye.js for chunk src_parent_js
     Transforming module ./src/parent.js for chunk src_parent_js
+    Transforming module ./src/another.js for chunk src_with2_js
+    Transforming module ./src/goodbye.js for chunk src_with2_js
+    Transforming module ./src/with2.js for chunk src_with2_js
 
 goodbye-v0.12-runtime compiled successfully"
 `;
@@ -25,17 +33,25 @@ exports[`Goodbye delay with node 6 target Compiles with correct debug log 1`] =
     Transforming module ./src/goodbye.js for chunk src_goodbye_js
     Transforming module ./src/goodbye.js for chunk src_parent_js
     Transforming module ./src/parent.js for chunk src_parent_js
+    Transforming module ./src/another.js for chunk src_with2_js
+    Transforming module ./src/goodbye.js for chunk src_with2_js
+    Transforming module ./src/with2.js for chunk src_with2_js
 
 goodbye-v6 compiled successfully"
 `;
 
 exports[`Goodbye delay with node 6 target using runtime Compiles with correct debug log 1`] = `
 "DEBUG LOG from TransformAsyncModulesPlugin
     Adding dependencies for top level await parsed in ./src/goodbye.js
+    Adding dependencies for top level await parsed in ./src/another.js
     Adding and reprocessing dependencies for ./src/parent.js
+    Adding and reprocessing dependencies for ./src/with2.js
     Transforming module ./src/goodbye.js for chunk src_goodbye_js
     Transforming module ./src/goodbye.js for chunk src_parent_js
     Transforming module ./src/parent.js for chunk src_parent_js
+    Transforming module ./src/another.js for chunk src_with2_js
+    Transforming module ./src/goodbye.js for chunk src_with2_js
+    Transforming module ./src/with2.js for chunk src_with2_js
 
 goodbye-v6-runtime compiled successfully"
 `;
@@ -45,6 +61,9 @@ exports[`Goodbye delay with node 8 target Compiles with correct debug log 1`] =
     Transforming module ./src/goodbye.js for chunk src_goodbye_js
     Transforming module ./src/goodbye.js for chunk src_parent_js
     Transforming module ./src/parent.js for chunk src_parent_js
+    Transforming module ./src/another.js for chunk src_with2_js
+    Transforming module ./src/goodbye.js for chunk src_with2_js
+    Transforming module ./src/with2.js for chunk src_with2_js
 
 goodbye-v8 compiled successfully"
 `;
@@ -54,6 +73,9 @@ exports[`Goodbye delay with node 8 target using runtime Compiles with correct de
     Transforming module ./src/goodbye.js for chunk src_goodbye_js
     Transforming module ./src/goodbye.js for chunk src_parent_js
     Transforming module ./src/parent.js for chunk src_parent_js
+    Transforming module ./src/another.js for chunk src_with2_js
+    Transforming module ./src/goodbye.js for chunk src_with2_js
+    Transforming module ./src/with2.js for chunk src_with2_js
 
 goodbye-v8-runtime compiled successfully"
 `;

test/src/another.js

@@ -0,0 +1,2 @@
+// Just another simple TLA
+export const zero = await Promise.resolve(0);

test/src/multiple.js

@@ -0,0 +1,2 @@
+// Same as chained but uses a parent with 2 dependencies.
+export const goodbye = import("./with2.js").then(({ pg }) => pg);

test/src/with2.js

@@ -0,0 +1,4 @@
+// This is the same as parent.js, except it also depends on another TLA.
+import * as pg from "./goodbye.js";
+import { zero } from "./another.js";
+export { pg, zero };