fix: support ESM templates in templates:install (require → dynamic import)

[AnujVishwakarma-src]

Problem

aio app add extension → templates:install runs the selected template with:

const gen = await env.instantiate(require(templatePath), { ... })

When a template ships as ESM (type: module), require(templatePath):

• throws ERR_REQUIRE_ESM on Node without require(esm), or
• on newer Node (20.19+/22.12+/24+) returns the module namespace { __esModule, default: <class> } — not the generator class.

Either way env.instantiate() gets a non-constructor and throws Error: constructor is not a constructor. This is hit today by @adobe/generator-app-excshell and @adobe/generator-app-asset-compute (both now ESM), since the Template Registry installs templates at @latest, bypassing semver pins.

Fix

Load the template resiliently and unwrap the default export (works for both CommonJS and ESM templates):

let templateModule
try {
  templateModule = require(templatePath)
} catch (e) {
  if (e.code === 'ERR_REQUIRE_ESM') {
    templateModule = await import(pathToFileURL(templatePath).href)
  } else {
    throw e
  }
}
const TemplateGenerator = (templateModule && templateModule.default) || templateModule
const gen = await env.instantiate(TemplateGenerator, { ... })

Tests

• New: ESM template (require throws ERR_REQUIRE_ESM → dynamic import(), real ESM fixture) instantiates the default-export class.
• New: a non-ERR_REQUIRE_ESM require error propagates.
• Existing CommonJS-template tests unchanged.
• Full suite: 153 tests, 100% coverage, lint clean.

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[AnujVishwakarma-src]

Findings

P1 / P2: ERR_REQUIRE_ASYNC_MODULE is not handled

In src/commands/templates/install.js, the fallback only catches:

if (e.code === 'ERR_REQUIRE_ESM') {
templateModule = await import(pathToFileURL(templatePath).href)
}

On newer Node versions, require() can load synchronous ESM directly. However, if the ESM template or anything in its import graph uses top-level await, Node throws ERR_REQUIRE_ASYNC_MODULE, not ERR_REQUIRE_ESM. Node explicitly documents that such modules must be loaded with import().

That means an otherwise valid ESM Yeoman template can still fail in the exact code path this PR is intended to fix.

Suggested change:

} catch (e) {
if (e.code === 'ERR_REQUIRE_ESM' || e.code === 'ERR_REQUIRE_ASYNC_MODULE') {
templateModule = await import(pathToFileURL(templatePath).href)
} else {
throw e
}
}

I would treat this as the main review comment.

[AnujVishwakarma-src]

Good catch — addressed in 94a520b.

require() now falls back to dynamic import() on both ERR_REQUIRE_ESM and ERR_REQUIRE_ASYNC_MODULE:

if (e.code === 'ERR_REQUIRE_ESM' || e.code === 'ERR_REQUIRE_ASYNC_MODULE') {
  templateModule = await import(pathToFileURL(templatePath).href)
} else {
  throw e
}

So an ESM template that uses top-level await (which throws ERR_REQUIRE_ASYNC_MODULE under require(esm) on newer Node) still loads correctly.

Added test/__fixtures__/esm-template-async/index.mjs (a fixture with top-level await) and a test covering the async-ESM path. Full suite: 154 tests, 100% coverage, lint clean.

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