test: add test for -R import-only-loader (#5391)

Author: legendecas

.knip.jsonc

@@ -18,6 +18,7 @@
   ],
   "ignoreDependencies": [
     "@mocha/docdash",
+    "@test/esm-only-loader",
     "coffeescript",
     "fake",
     "jsdoc-ts-utils",

package-lock.json

@@ -127,6 +127,7 @@
     "@rollup/plugin-json": "^4.1.0",
     "@rollup/plugin-multi-entry": "^4.0.1",
     "@rollup/plugin-node-resolve": "^13.1.3",
+    "@test/esm-only-loader": "./test/compiler-fixtures/esm-only-loader",
     "chai": "^4.3.4",
     "coffeescript": "^2.6.1",
     "cross-env": "^7.0.2",

package.json

@@ -0,0 +1,14 @@
+Test package used to cover a loader package that is only defined with `exports.imports` in the `package.json`.
+
+This must be linked to `node_modules` and be `require`/`import`-ed with a bare specifier, as
+defined in algorithm [`ESM_RESOLVE`][] step 5.2:
+
+```
+ESM_RESOLVE(specifier, parentURL)
+  ...
+  5. Otherwise,
+    1. Note: specifier is now a bare specifier.
+    2. Set resolved the result of PACKAGE_RESOLVE(specifier, parentURL).
+```
+
+[`ESM_RESOLVE`]: https://nodejs.org/api/esm.html?fts_query=algorithm#resolution-algorithm-specification

test/compiler-fixtures/esm-only-loader/README.md

@@ -0,0 +1,15 @@
+import fsPromises from 'node:fs/promises';
+import { fileURLToPath } from 'node:url';
+
+export async function load(url, context, nextLoad) {
+  if (!url.includes('compiler-esm') && !url.includes('compiler-cjs')) {
+    return nextLoad(url, context);
+  }
+  const format = url.includes('compiler-esm') ? 'module' : 'commonjs';
+  const content = await fsPromises.readFile(fileURLToPath(url + '.compiled'), 'utf8');
+  return {
+    format,
+    source: content,
+    shortCircuit: true,
+  }
+}

test/compiler-fixtures/esm-only-loader/esm-loader.fixture.mjs

@@ -0,0 +1,3 @@
+import Module from 'node:module';
+
+Module.register(new URL('./esm-loader.fixture.mjs', import.meta.url));

test/compiler-fixtures/esm-only-loader/esm.fixture.js

@@ -0,0 +1,9 @@
+{
+  "name": "@test/esm-only-loader",
+  "type": "module",
+  "exports": {
+    ".": {
+      "import": "./esm.fixture.js"
+    }
+  }
+}

test/compiler-fixtures/esm-only-loader/package.json

@@ -0,0 +1,71 @@
+'use strict';
+
+var exec = require('node:child_process').exec;
+var path = require('node:path');
+
+// Regression test for https://github.com/mochajs/mocha/issues/5380
+describe('support ESM only module loader packages', function () {
+  it('should support ESM .js extension', function (done) {
+    exec(
+      '"' +
+        process.execPath +
+        '" "' +
+        path.join('bin', 'mocha') +
+        '" -R json --require "@test/esm-only-loader" "test/compiler-esm/*.js"',
+      {cwd: path.join(__dirname, '..', '..')},
+      function (error, stdout) {
+        if (error && !stdout) {
+          return done(error);
+        }
+        var results = JSON.parse(stdout);
+        expect(results, 'to have property', 'tests');
+        var titles = [];
+        for (var index = 0; index < results.tests.length; index += 1) {
+          expect(results.tests[index], 'to have property', 'fullTitle');
+          titles.push(results.tests[index].fullTitle);
+        }
+        expect(
+          titles,
+          'to contain',
+          'esm written in esm should work',
+        ).and(
+          'to contain',
+          'esm written in esm with top-level-await should work',
+        ).and('to have length', 2);
+        done();
+      }
+    );
+  });
+
+  it('should support ESM .ts extension', function (done) {
+    exec(
+      '"' +
+        process.execPath +
+        '" "' +
+        path.join('bin', 'mocha') +
+        '" -R json --require "@test/esm-only-loader" "test/compiler-esm/*.ts"',
+      {cwd: path.join(__dirname, '..', '..')},
+      function (error, stdout) {
+        if (error && !stdout) {
+          return done(error);
+        }
+        var results = JSON.parse(stdout);
+        expect(results, 'to have property', 'tests');
+        var titles = [];
+        for (var index = 0; index < results.tests.length; index += 1) {
+          expect(results.tests[index], 'to have property', 'fullTitle');
+          titles.push(results.tests[index].fullTitle);
+        }
+        expect(
+          titles,
+          'to contain',
+          'esm written in esm should work',
+        ).and(
+          'to contain',
+          'esm written in esm with top-level-await should work',
+        ).and('to have length', 2);
+        done();
+      }
+    );
+  });
+});