Fix ESM build to contain import statements with full file extensions

.github/actions/ci-common-setup/action.yaml

@@ -22,7 +22,7 @@ runs:
       shell: bash
 
     - name: Install pnpm
-      run: npm install -g pnpm
+      run: npm install -g pnpm@^8
       shell: bash
 
     - name: Restore possibly cached dependencies

.mocharc.yml

@@ -1,4 +1,6 @@
 spec: ./spec/**/*.spec.ts
+file:
+  - ./spec/testsGlobalSetup.ts
 watch-files:
   - ./src/**/*.ts
   - ./spec/**/*.ts

package.json

@@ -29,6 +29,7 @@
     "typescript",
     "esm"
   ],
+  "type": "commonjs",
   "engines": {
     "node": ">=10.21.0"
   },
@@ -46,9 +47,9 @@
     "dist"
   ],
   "scripts": {
-    "test": "ts-mocha -p ./tsconfig-cjs.json",
-    "build": "rimraf ./dist && tsc -p tsconfig-esm.json && tsc -p tsconfig-cjs.json && ts-node ./scripts/set-module-type-in-dist-builds.ts",
-    "check-typings": "tsc --noEmit -p ./tsconfig-esm.json",
+    "test": "ts-mocha -p ./spec/tsconfig-tests.json",
+    "build": "rimraf ./dist && tsc -p tsconfig.json && tsc -p tsconfig-cjs.json && ts-node -p tsconfig.json ./scripts/set-module-type-in-dist-builds.ts",
+    "check-typings": "tsc --noEmit -p ./tsconfig.json",
     "prepublishOnly": "npm run build"
   },
   "devDependencies": {
@@ -61,7 +62,7 @@
     "eslint-config-prettier": "^8.9.0",
     "eslint-config-standard": "^17.1.0",
     "expect": "^29.6.2",
-    "mocha": "^10.2.0",
+    "mocha": "^10.4.0",
     "prettier": "^3.0.2",
     "rimraf": "^5.0.1",
     "sinon": "^15.2.0",

spec/iterified.spec.ts

@@ -1,11 +1,11 @@
 import 'mocha';
 import expect from 'expect';
 import * as sinon from 'sinon';
-import { iterified, type ExecutorFn } from '../src';
-import nextTick from './utils/nextTick';
-import getPromiseState from './utils/getPromiseState';
-import collectAsyncIterable from './utils/collectAsyncIterable';
-import sortPromisesByResolutionOrder from './utils/sortPromisesByResolutionOrder';
+import { iterified, type ExecutorFn } from '../src/index.js';
+import nextTick from './utils/nextTick.js';
+import getPromiseState from './utils/getPromiseState.js';
+import collectAsyncIterable from './utils/collectAsyncIterable.js';
+import sortPromisesByResolutionOrder from './utils/sortPromisesByResolutionOrder.js';
 
 describe('`iterified` function', () => {
   it('generating a single value and consuming via multiple iterators', async () => {

spec/iterifiedUnwrapped.spec.ts

@@ -1,8 +1,8 @@
 import 'mocha';
 import expect from 'expect';
-import { iterifiedUnwrapped } from '../src';
-import getPromiseState from './utils/getPromiseState';
-import collectAsyncIterable from './utils/collectAsyncIterable';
+import { iterifiedUnwrapped } from '../src/index.js';
+import getPromiseState from './utils/getPromiseState.js';
+import collectAsyncIterable from './utils/collectAsyncIterable.js';
 
 describe('`iterifiedUnwrapped` function', () => {
   it('generating a single value and consuming via multiple iterators', async () => {

spec/testsGlobalSetup.ts

@@ -0,0 +1,25 @@
+import mod from 'module';
+
+(() => {
+  /*
+    It appears that `ts-mocha` errors out on import statements with paths having explicit `.js` extension.
+    However, the `.js` extensions currently present on all imports across the project CANNOT be omitted for the sake of running the tests
+    since without them, while TypeScript is able to accept extension-less imports as well (having set `"moduleResolution": "NodeNext"` in `tsconfig.json`),
+    when fed such imports while compiling to an ESM format, it would output them as-are. ESM code with extension-less imports is
+    INVALID ESM code, so the build output is actually non-executable even though it would complete without any issue from
+    the TypeScript compilation.
+    To work around this (only during test run-time) - we're patching Node's file import mechanism to intercept
+    every `.js`-ending import path and feed it back to Node as itself-minus-the-`.js` extension. This way,
+    as long as we've set `"module": "commonjs"` in `tsconfig.json` that accompanies our test runs, we can still write
+    the entire code-base with "fully-qualified" ESM-compatible imports statements AS WELL AS have Mocha be able to
+    execute over the same code without issues.
+    Inspired by https://github.com/ReactiveX/rxjs/blob/6d011f0dc67b736adc0979d3bc14d93b49064efa/spec/support/mocha-path-mappings.js
+  */
+
+  const origResolveFilename = (mod as any)._resolveFilename;
+
+  (mod as any)._resolveFilename = function (path: string, ...rest: unknown[]) {
+    const pathPossiblyPatched = path.endsWith('.js') ? path.slice(0, -3) : path;
+    return origResolveFilename.call(this, pathPossiblyPatched, ...rest);
+  };
+})();

spec/tsconfig-tests.json

@@ -0,0 +1,10 @@
+{
+  "$schema": "https://json.schemastore.org/tsconfig",
+  "include": ["./**/*.ts"],
+  "extends": "../tsconfig.json",
+  "compilerOptions": {
+    "noEmit": true,
+    "module": "NodeNext",
+    "moduleResolution": "NodeNext"
+  }
+}

src/index.ts

@@ -5,8 +5,8 @@ import {
   type ExecutorFn,
   type TeardownFn,
   type Iterified,
-} from './iterified';
-import { iterifiedUnwrapped, type IterifiedUnwrapped } from './iterifiedUnwrapped';
+} from './iterified.js';
+import { iterifiedUnwrapped, type IterifiedUnwrapped } from './iterifiedUnwrapped.js';
 
 export {
   iterified,

src/iterified.ts

@@ -1,5 +1,5 @@
-import { createMulticastChannel } from './utils/createMulticastChannel';
-import { type MaybePromise } from './utils/types/MaybePromise';
+import { createMulticastChannel } from './utils/createMulticastChannel.js';
+import { type MaybePromise } from './utils/types/MaybePromise.js';
 
 export {
   iterified,

src/iterifiedUnwrapped.ts

@@ -1,5 +1,5 @@
-import { type IterifiedIterable } from './iterified';
-import { createMulticastChannel } from './utils/createMulticastChannel';
+import { type IterifiedIterable } from './iterified.js';
+import { createMulticastChannel } from './utils/createMulticastChannel.js';
 
 export { iterifiedUnwrapped, type IterifiedUnwrapped };
 

src/utils/createMulticastChannel.ts

@@ -1,5 +1,5 @@
-import { Deferred } from './createDeferred';
-import { type MaybePromise } from './types/MaybePromise';
+import { Deferred } from './createDeferred.js';
+import { type MaybePromise } from './types/MaybePromise.js';
 
 export { createMulticastChannel, type MulticastChannel, type MulticastChannelIterator };
 

tsconfig-cjs.json

@@ -1,9 +1,10 @@
 {
   "$schema": "https://json.schemastore.org/tsconfig",
-  "files": ["./src/index.ts"],
-  "extends": "./tsconfig-esm.json",
+  "include": ["./src/**/*.ts"],
+  "extends": "./tsconfig.json",
   "compilerOptions": {
     "outDir": "./dist/cjs",
-    "module": "CommonJS"
+    "module": "CommonJS",
+    "moduleResolution": "Node10"
   }
-}
+}

tsconfig-esm.json → tsconfig.json

@@ -1,9 +1,10 @@
 {
   "$schema": "https://json.schemastore.org/tsconfig",
-  "files": ["./src/index.ts"],
+  "include": ["./src/**/*.ts"],
   "compilerOptions": {
     "outDir": "./dist/esm",
-    "module": "ESNext",
+    "module": "NodeNext",
+    "moduleResolution": "NodeNext",
     "target": "es2019",
     "strict": true,
     "noImplicitAny": true,