ESM: fix swallowing MODULE_NOT_FOUND errors in case of type:module (#…

…4687)

lib/esm-utils.js

@@ -52,7 +52,21 @@ exports.requireOrImport = hasStableEsmImplementation
           err.code === 'ERR_UNKNOWN_FILE_EXTENSION' ||
           err.code === 'ERR_UNSUPPORTED_DIR_IMPORT'
         ) {
-          return require(file);
+          try {
+            return require(file);
+          } catch (requireErr) {
+            if (requireErr.code === 'ERR_REQUIRE_ESM') {
+              // This happens when the test file is a JS file, but via type:module is actually ESM,
+              // AND has an import to a file that doesn't exist.
+              // This throws an `ERR_MODULE_NOT_FOUND` // error above,
+              // and when we try to `require` it here, it throws an `ERR_REQUIRE_ESM`.
+              // What we want to do is throw the original error (the `ERR_MODULE_NOT_FOUND`),
+              // and not the `ERR_REQUIRE_ESM` error, which is a red herring.
+              throw err;
+            } else {
+              throw requireErr;
+            }
+          }
         } else {
           throw err;
         }

test/integration/esm.spec.js

@@ -1,8 +1,6 @@
 'use strict';
 var path = require('path');
-var helpers = require('./helpers');
-var run = helpers.runMochaJSON;
-var runMochaAsync = helpers.runMochaAsync;
+const {runMochaJSON: run, runMochaAsync} = require('./helpers');
 var utils = require('../../lib/utils');
 var args =
   +process.versions.node.split('.')[0] >= 13 ? [] : ['--experimental-modules'];
@@ -81,4 +79,18 @@ describe('esm', function() {
 
     expect(result, 'to have passed test count', 1);
   });
+
+  it('should throw an ERR_MODULE_NOT_FOUND and not ERR_REQUIRE_ESM if file imports a non-existing module', async function() {
+    const fixture =
+      'esm/type-module/test-that-imports-non-existing-module.fixture.js';
+
+    const err = await runMochaAsync(fixture, ['--unhandled-rejections=warn'], {
+      stdio: 'pipe'
+    }).catch(err => err);
+
+    expect(err.output, 'to contain', 'ERR_MODULE_NOT_FOUND').and(
+      'to contain',
+      'test-that-imports-non-existing-module'
+    );
+  });
 });

test/integration/fixtures/esm/type-module/package.json

@@ -0,0 +1,3 @@
+{
+  "type": "module"
+}

test/integration/fixtures/esm/type-module/test-that-imports-non-existing-module.fixture.js

@@ -0,0 +1,6 @@
+import assert from 'assert';
+import './this-module-does-not-exist.js';
+
+it('should not pass (or even run) because above import will fail', () => {
+  assert(true);
+});