Improve ESM compatibility

This change follows the solution described in [1] to make the package
play nice with both CommonJS and ESM clients.

This includes:

* Changing imports to use the .js extension explicitly
* Modifying the dist/package.json file to refer to different directories
  depending on the context
* Providing two package.json files that override the package type
  depending on the context

Fixes: GH-37

[1] https://www.sensedeep.com/blog/posts/2021/how-to-create-single-source-npm-module.html

jest.config.js

@@ -17,4 +17,8 @@ module.exports = {
             statements: 100,
         },
     },
+    moduleNameMapper: {
+      "^(.*)\\.js$": "$1"
+    },
+
 };

package-cjs.json

@@ -0,0 +1 @@
+{"type": "commonjs"}

package-esm.json

@@ -0,0 +1 @@
+{"type": "module"}

package.json

@@ -5,8 +5,8 @@
   "private": true,
   "scripts": {
     "build": "npm run clean && npm run build:ts && npm run build:copy",
-    "build:ts": "tsc -p tsconfig.json && tsc -p tsconfig.json -m esnext --outDir dist/esm/ -d false -declarationMap false",
-    "build:copy": "copyfiles README.md LICENSE src/package.json dist --flat && copyfiles src/rxjs-operators/package.json dist --up 1",
+    "build:ts": "tsc -p tsconfig-cjs.json && tsc -p tsconfig-esm.json",
+    "build:copy": "copyfiles README.md LICENSE src/package.json dist --flat && copyfiles src/rxjs-operators/package.json dist/cjs --up 1 && cp package-cjs.json dist/cjs/package.json && cp package-esm.json dist/esm/package.json",
     "clean": "rm -rf dist",
     "test": "jest",
     "format": "prettier . --write"

src/index.ts

@@ -1,2 +1,2 @@
-export * from './result';
-export * from './option';
+export * from './result.js';
+export * from './option.js';

src/option.ts

@@ -1,5 +1,5 @@
-import { toString } from './utils';
-import { Result, Ok, Err } from './result';
+import { toString } from './utils.js';
+import { Result, Ok, Err } from './result.js';
 
 interface BaseOption<T> extends Iterable<T extends Iterable<infer U> ? U : never> {
     /** `true` when the Option is Some */ readonly some: boolean;

src/package.json

@@ -2,9 +2,15 @@
   "name": "ts-results",
   "version": "3.3.0",
   "description": "A typescript implementation of Rust's Result and Option objects.",
-  "main": "index.js",
-  "module": "./esm/index.js",
-  "types": "index.d.ts",
+  "main": "cjs/index.js",
+  "module": "esm/index.js",
+  "types": "esm/index.d.ts",
+  "exports": {
+      ".": {
+          "import": "./esm/index.js",
+          "require": "./cjs/index.js"
+      }
+  },
   "keywords": [
     "Rust",
     "Result",

src/result.ts

@@ -1,5 +1,5 @@
-import { toString } from './utils';
-import { Option, None, Some } from './option';
+import { toString } from './utils.js';
+import { Option, None, Some } from './option.js';
 
 /*
  * Missing Rust Result type methods:

src/rxjs-operators/index.ts

@@ -1,6 +1,6 @@
 import { MonoTypeOperatorFunction, Observable, ObservableInput, of, OperatorFunction } from 'rxjs';
 import { filter, map, mergeMap, switchMap, tap } from 'rxjs/operators';
-import { Err, Ok, Result } from '../index';
+import { Err, Ok, Result } from '../index.js';
 
 export function resultMap<T, T2, E>(mapper: (val: T) => T2): OperatorFunction<Result<T, E>, Result<T2, E>> {
     return (source) => {

src/rxjs-operators/package.json

@@ -2,5 +2,5 @@
   "name": "ts-results/rxjs-operators",
   "types": "index.d.ts",
   "main": "index.js",
-  "module": "../esm/rxjs-operators/index.js"
+  "module": "../../esm/rxjs-operators/index.js"
 }

test/err.test.ts

@@ -1,6 +1,6 @@
 import { assert } from 'conditional-type-checks';
-import { Err, Ok } from '../src';
-import { eq, expect_never } from './util';
+import { Err, Ok } from '../src/index.js';
+import { eq, expect_never } from './util.js';
 
 test('Constructable & Callable', () => {
     const a = new Err(3);

test/ok.test.ts

@@ -1,6 +1,6 @@
 import { assert } from 'conditional-type-checks';
-import { Err, Ok, Result } from '../src';
-import { eq, expect_never, expect_string } from './util';
+import { Err, Ok, Result } from '../src/index.js';
+import { eq, expect_never, expect_string } from './util.js';
 
 test('Constructable & Callable', () => {
     const a = new Ok(3);

test/option.test.ts

@@ -1,5 +1,5 @@
-import { Err, None, Ok, Option, OptionSomeType, Result, Some } from '../src';
-import { eq } from './util';
+import { Err, None, Ok, Option, OptionSomeType, Result, Some } from '../src/index.js';
+import { eq } from './util.js';
 
 const someString = Some('foo');
 const someNum = new Some(10);

test/result.test.ts

@@ -9,8 +9,8 @@ import {
     ResultOkType,
     ResultOkTypes,
     Some,
-} from '../src';
-import { eq } from './util';
+} from '../src/index.js';
+import { eq } from './util.js';
 
 test('Err<E> | Ok<T> should be Result<T, E>', () => {
     const r1 = Err(0);

test/rxjs.test.ts

@@ -1,4 +1,4 @@
-import { Err, Ok, Result } from '../src';
+import { Err, Ok, Result } from '../src/index.js';
 import { Observable, of } from 'rxjs';
 import {
     elseMap,
@@ -13,8 +13,8 @@ import {
     resultSwitchMap,
     tapResultErr,
     tapResultOk,
-} from '../src/rxjs-operators';
-import { eq } from './util';
+} from '../src/rxjs-operators/index.js';
+import { eq } from './util.js';
 
 const goodVal: Observable<Result<string, number>> = of(Ok('good'));
 const badVal: Observable<Result<string, number>> = of(Err(0));

test/tsconfig.json

@@ -1,5 +1,5 @@
 {
-  "extends": "../tsconfig.json",
+  "extends": "../tsconfig-cjs.json",
   "compilerOptions": {
     "baseUrl": "./",
     "sourceMap": true,

test/util.ts

@@ -1,5 +1,5 @@
 import { IsExact, IsNever } from 'conditional-type-checks';
-import { Result } from '../src';
+import { Result } from '../src/index.js';
 import { Observable } from 'rxjs';
 
 export function expect_string<T>(x: T, y: IsExact<T, string>) {}

tsconfig-cjs.json

@@ -0,0 +1,7 @@
+{
+    "extends": "./tsconfig-base.json",
+    "compilerOptions": {
+        "outDir": "./dist/cjs",
+        "module": "commonjs"
+    }
+}

tsconfig-esm.json

@@ -0,0 +1,7 @@
+{
+    "extends": "./tsconfig-base.json",
+    "compilerOptions": {
+        "outDir": "dist/esm",
+        "module": "esnext"
+    }
+}