NodeJS ESM extensions aren't supported

[AlexCannonball]

ESM support for NodeJS extensions was added in VS Code 1.100.0 ( microsoft/vscode#245214).

@vscode/test-cli tests with Mocha worked for my CJS extension.

I've migrated the extension to ESM and @vscode/test-electron runner works for the tests. However, I get the following error when trying to run tests via @vscode/test-cli:

Error: Cannot find package 'vscode' imported from d:\code_repository\extension\test-compiled\suite\diagnostics.spec.js
        at packageResolve (node:internal/modules/esm/resolve:880:9)
        at moduleResolve (node:internal/modules/esm/resolve:953:18)
        at defaultResolve (node:internal/modules/esm/resolve:1195:11)
        at ModuleLoader.defaultResolve (node:internal/modules/esm/loader:642:12)
        at #cachedDefaultResolve (node:internal/modules/esm/loader:591:25)
        at ModuleLoader.getModuleJobForRequire (node:internal/modules/esm/loader:347:53)
        at new ModuleJobSync (node:internal/modules/esm/module_job:333:34)
        at ModuleLoader.importSyncForRequire (node:internal/modules/esm/loader:320:11)
        at loadESMFromCJS (node:internal/modules/cjs/loader:1378:24)
        at Module._compile (node:internal/modules/cjs/loader:1518:5)
        at Module._extensions..js (node:internal/modules/cjs/loader:1588:16)
        at Module.load (node:internal/modules/cjs/loader:1282:32)
        at Module._load (node:internal/modules/cjs/loader:1103:12)
        at c._load (node:electron/js2c/node_init:2:16955)
        at e._load (file:///d:/code_repository/extension/.vscode-test/vscode-win32-x64-archive-1.100.2/resources/app/out/vs/workbench/api/node/extensionHostProcess.js:225:1509)
        at t._load (file:///d:/code_repository/extension/.vscode-test/vscode-win32-x64-archive-1.100.2/resources/app/out/vs/workbench/api/node/extensionHostProcess.js:180:22628)
        at r._load (file:///d:/code_repository/extension/.vscode-test/vscode-win32-x64-archive-1.100.2/resources/app/out/vs/workbench/api/node/extensionHostProcess.js:172:22062)
        at Module.require (node:internal/modules/cjs/loader:1305:19)
        at require (node:internal/modules/helpers:182:18)
        at d:\code_repository\extension\node_modules\@vscode\test-cli\node_modules\mocha\lib\mocha.js:416:36
        at Array.forEach (<anonymous>)
        at Mocha.loadFiles (d:\code_repository\extension\node_modules\@vscode\test-cli\node_modules\mocha\lib\mocha.js:413:14)
        at Mocha.run (d:\code_repository\extension\node_modules\@vscode\test-cli\node_modules\mocha\lib\mocha.js:988:10)
        at mochaGlobalTeardown.mochaGlobalTeardown (d:\code_repository\extension\node_modules\@vscode\test-cli\out\runner.cjs:33:50)
        at new Promise (<anonymous>)
        at Object.run (d:\code_repository\extension\node_modules\@vscode\test-cli\out\runner.cjs:33:11)
        at file:///d:/code_repository/extension/.vscode-test/vscode-win32-x64-archive-1.100.2/resources/app/out/vs/workbench/api/node/extensionHostProcess.js:123:17846
        at new Promise (<anonymous>)
        at PJ.sb (file:///d:/code_repository/extension/.vscode-test/vscode-win32-x64-archive-1.100.2/resources/app/out/vs/workbench/api/node/extensionHostProcess.js:123:17567)
        at process.processTicksAndRejections (node:internal/process/task_queues:95:5)
        at async PJ.$extensionTestsExecute (file:///d:/code_repository/extension/.vscode-test/vscode-win32-x64-archive-1.100.2/resources/app/out/vs/workbench/api/node/extensionHostProcess.js:123:17155)

https://github.com/jrieken/vscode-esm-sample-extension shows a workaround how to run tests via @vscode/test-electron but it doesn't seem applicable to @vscode/test-cli.

The page https://code.visualstudio.com/api/working-with-extensions/testing-extension#quick-setup-the-test-cli doesn't include steps for ESM extensions as well.

[AlexCannonball]

Probably, related to microsoft/vscode#285297