Migrate to ESM and upgrade dependencies (#752)

* Migrate to ESM and upgrade dependencies

* Address review: use type-only import for QualityOptions

* update version to 6.0.0 in package.json and package-lock.json

* Add ESM migration note to README for V6

* Update test imports for ESM and clean up devDependencies (ts-node, @types/jest)

* Pin @types/node to 24.x and refine tsconfig/README wording

src/cache-restore.ts

@@ -4,8 +4,8 @@ import * as cache from '@actions/cache';
 import * as core from '@actions/core';
 import * as glob from '@actions/glob';
 
-import {getNuGetFolderPath} from './cache-utils';
-import {lockFilePatterns, State, Outputs} from './constants';
+import {getNuGetFolderPath} from './cache-utils.js';
+import {lockFilePatterns, State, Outputs} from './constants.js';
 
 export const restoreCache = async (cacheDependencyPath?: string) => {
   const lockFilePath = cacheDependencyPath || (await findLockFile());

src/cache-save.ts

@@ -1,8 +1,8 @@
 import * as core from '@actions/core';
 import * as cache from '@actions/cache';
 import fs from 'node:fs';
-import {getNuGetFolderPath} from './cache-utils';
-import {State} from './constants';
+import {getNuGetFolderPath} from './cache-utils.js';
+import {State} from './constants.js';
 
 // Catch and log any unhandled exceptions.  These exceptions can leak out of the uploadChunk method in
 // @actions/toolkit when a failed upload closes the file descriptor causing any in-process reads to

src/cache-utils.ts

@@ -2,7 +2,7 @@ import * as cache from '@actions/cache';
 import * as core from '@actions/core';
 import * as exec from '@actions/exec';
 
-import {cliCommand} from './constants';
+import {cliCommand} from './constants.js';
 
 type NuGetFolderName =
   | 'http-cache'

src/installer.ts

@@ -5,10 +5,11 @@ import * as io from '@actions/io';
 import * as hc from '@actions/http-client';
 import {chmodSync} from 'fs';
 import path from 'path';
+import {fileURLToPath} from 'url';
 import os from 'os';
 import semver from 'semver';
-import {IS_WINDOWS, PLATFORM} from './utils';
-import {QualityOptions} from './setup-dotnet';
+import {IS_WINDOWS, PLATFORM} from './utils.js';
+import type {QualityOptions} from './setup-dotnet.js';
 
 export interface DotnetVersion {
   type: string;
@@ -233,7 +234,13 @@ export class DotnetInstallScript {
 
   constructor() {
     this.escapedScript = path
-      .join(__dirname, '..', '..', 'externals', this.scriptName)
+      .join(
+        path.dirname(fileURLToPath(import.meta.url)),
+        '..',
+        '..',
+        'externals',
+        this.scriptName
+      )
       .replace(/'/g, "''");
 
     if (IS_WINDOWS) {

src/setup-dotnet.ts

@@ -4,15 +4,16 @@ import {
   DotnetCoreInstaller,
   DotnetInstallDir,
   normalizeArch
-} from './installer';
+} from './installer.js';
 import * as fs from 'fs';
 import path from 'path';
+import {fileURLToPath} from 'url';
 import semver from 'semver';
 import os from 'os';
-import * as auth from './authutil';
-import {isCacheFeatureAvailable} from './cache-utils';
-import {restoreCache} from './cache-restore';
-import {Outputs} from './constants';
+import * as auth from './authutil.js';
+import {isCacheFeatureAvailable} from './cache-utils.js';
+import {restoreCache} from './cache-restore.js';
+import {Outputs} from './constants.js';
 import JSON5 from 'json5';
 
 const qualityOptions = ['daily', 'preview', 'ga'] as const;
@@ -152,7 +153,8 @@ export async function run() {
             await exec.exec('dotnet', ['workload', 'install', ...workloads]);
           } catch (err) {
             throw new Error(
-              `Failed to install workloads [${workloads.join(', ')}]: ${err}`
+              `Failed to install workloads [${workloads.join(', ')}]: ${err}`,
+              {cause: err}
             );
           }
         }
@@ -172,7 +174,12 @@ export async function run() {
       await restoreCache(cacheDependencyPath);
     }
 
-    const matchersPath = path.join(__dirname, '..', '..', '.github');
+    const matchersPath = path.join(
+      path.dirname(fileURLToPath(import.meta.url)),
+      '..',
+      '..',
+      '.github'
+    );
     core.info(`##[add-matcher]${path.join(matchersPath, 'csc.json')}`);
   } catch (error) {
     core.setFailed(error.message);