fix(package): specify side-effects in package.json

This prevents bundlers from tree-shaking Web Streams API compatibility extensions.

Closes #382

Author: mayorandrew

gulp/package-task.js

@@ -1,25 +1,61 @@
-import { metadataFiles, packageJSONFields, npmPkgName, npmOrgName, targetDir, packageName, observableFromStreams } from './util.js';
+import {
+  metadataFiles,
+  npmOrgName,
+  npmPkgName,
+  observableFromStreams,
+  packageJSONFields,
+  packageName,
+  targetDir,
+} from './util.js';
 
 import gulp from 'gulp';
 import { memoizeTask } from './memoize-task.js';
 import { EMPTY as ObservableEmpty, forkJoin as ObservableForkJoin } from 'rxjs';
 import gulpJsonTransform from 'gulp-json-transform';
+import { sync as globSync } from 'glob';
+import path from 'node:path';
 
-export const packageTask = ((cache) => memoizeTask(cache, function bundle(target, format) {
+export const packageTask = ((cache) =>
+  memoizeTask(cache, function bundle(target, format) {
     if (target === `src`) return ObservableEmpty();
     const out = targetDir(target, format);
-    const jsonTransform = gulpJsonTransform(target === npmPkgName ? createMainPackageJson(target, format) :
-        target === `ts` ? createTypeScriptPackageJson(target, format)
-            : createScopedPackageJSON(target, format),
-        2);
+    const jsonTransform = gulpJsonTransform(
+      target === npmPkgName
+        ? createMainPackageJson(target, format)
+        : target === `ts`
+        ? createTypeScriptPackageJson(target, format)
+        : createScopedPackageJSON(target, format),
+      2
+    );
     return ObservableForkJoin([
-        observableFromStreams(gulp.src(metadataFiles), gulp.dest(out)), // copy metadata files
-        observableFromStreams(gulp.src(`package.json`), jsonTransform, gulp.dest(out)) // write packageJSONs
+      observableFromStreams(gulp.src(metadataFiles), gulp.dest(out)), // copy metadata files
+      observableFromStreams(gulp.src(`package.json`), jsonTransform, gulp.dest(out)), // write packageJSONs
     ]).toPromise();
-}))({});
+  }))({});
 
 export default packageTask;
 
+function createSideEffectsList() {
+    const patterns = ['add/**/*.ts', 'asynciterable/todomstream.ts'];
+
+    const tsFilePaths = globSync(patterns.map((p) => `./src/${p}`));
+
+    // Generate .mjs and .js paths for each .ts file
+    const sideEffectPaths = [];
+    for (const filePath of tsFilePaths) {
+        // Get the relative path from srcDir to the file
+        const relativePath = path.relative('./src', filePath);
+        // Normalize path separators to forward slashes
+        const normalizedPath = relativePath.replace(/\\/g, '/');
+        // Remove the .ts extension and add .mjs and .js
+        const basePath = normalizedPath.replace(/\.ts$/, '');
+        sideEffectPaths.push(`./${basePath}.mjs`);
+        sideEffectPaths.push(`./${basePath}.js`);
+    }
+
+    return sideEffectPaths;
+}
+
 const createMainPackageJson = (target, format) => (orig) => ({
     ...createTypeScriptPackageJson(target, format)(orig),
     bin: orig.bin,
@@ -48,7 +84,7 @@ const createMainPackageJson = (target, format) => (orig) => ({
         },
         './*': createDualExport('*'),
     },
-    sideEffects: false,
+    sideEffects: createSideEffectsList(),
     esm: { mode: `all`, sourceMap: true }
 });
 
@@ -60,7 +96,7 @@ const createTypeScriptPackageJson = (target, format) => (orig) => ({
     types: `node.ts`,
     browser: `dom.ts`,
     type: 'module',
-    sideEffects: false,
+    sideEffects: createSideEffectsList(),
     esm: { mode: `auto`, sourceMap: true },
     dependencies: {
         '@types/node': '*',
@@ -88,7 +124,7 @@ const createScopedPackageJSON = (target, format) => (({ name, ...orig }) =>
             // set "module" if building scoped ESM target
             module: format === 'esm' || format === 'cls' ? `node.js` : undefined,
             // set "sideEffects" to false as a hint to Webpack that it's safe to tree-shake the ESM target
-            sideEffects: format === 'esm' || format === 'cls' ? false : undefined,
+            sideEffects: format === 'esm' || format === 'cls' ? createSideEffectsList() : undefined,
             // include "esm" settings for https://www.npmjs.com/package/esm if building scoped ESM target
             esm: format === `esm` ? { mode: `auto`, sourceMap: true } : undefined,
             // set "types" to "dom" if building scoped UMD target, otherwise "node"