module: add warning when import,export is detected in CJS context

This will allow users to know how to change their project to support
ES modules.

PR-URL: https://github.com/nodejs/node/pull/28950
Reviewed-By: Bradley Farias <bradley.meck@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Guy Bedford <guybedford@gmail.com>

1 files changed, 136 insertions, 0 deletions

diff --git a/test/es-module/test-esm-cjs-load-error-note.mjs b/test/es-module/test-esm-cjs-load-error-note.mjs
new file mode 100644
index 0000000000..ce0d1d7969
--- /dev/null
+++ b/test/es-module/test-esm-cjs-load-error-note.mjs
@@ -0,0 +1,136 @@
+// Flags: --experimental-modules
+
+import { mustCall } from '../common/index.mjs';
+import assert from 'assert';
+import fixtures from '../common/fixtures.js';
+import { spawn } from 'child_process';
+
+const Export1 = fixtures.path('/es-modules/es-note-unexpected-export-1.cjs');
+const Export2 = fixtures.path('/es-modules/es-note-unexpected-export-2.cjs');
+const Import1 = fixtures.path('/es-modules/es-note-unexpected-import-1.cjs');
+const Import2 = fixtures.path('/es-modules/es-note-promiserej-import-2.cjs');
+const Import3 = fixtures.path('/es-modules/es-note-unexpected-import-3.cjs');
+const Import4 = fixtures.path('/es-modules/es-note-unexpected-import-4.cjs');
+const Import5 = fixtures.path('/es-modules/es-note-unexpected-import-5.cjs');
+
+// Expect note to be included in the error output
+const expectedNote = 'To load an ES module, ' +
+'set "type": "module" in the package.json ' +
+'or use the .mjs extension.';
+
+const expectedCode = 1;
+
+const pExport1 = spawn(process.execPath, ['--experimental-modules', Export1]);
+let pExport1Stderr = '';
+pExport1.stderr.setEncoding('utf8');
+pExport1.stderr.on('data', (data) => {
+  pExport1Stderr += data;
+});
+pExport1.on('close', mustCall((code) => {
+  assert.strictEqual(code, expectedCode);
+  assert.ok(pExport1Stderr.includes(expectedNote),
+            `${expectedNote} not found in ${pExport1Stderr}`);
+}));
+
+
+const pExport2 = spawn(process.execPath, ['--experimental-modules', Export2]);
+let pExport2Stderr = '';
+pExport2.stderr.setEncoding('utf8');
+pExport2.stderr.on('data', (data) => {
+  pExport2Stderr += data;
+});
+pExport2.on('close', mustCall((code) => {
+  assert.strictEqual(code, expectedCode);
+  assert.ok(pExport2Stderr.includes(expectedNote),
+            `${expectedNote} not found in ${pExport2Stderr}`);
+}));
+// The flag --experimental-modules is not used here
+// the note must not be included in the output
+const pExport3 = spawn(process.execPath, [Export1]);
+let pExport3Stderr = '';
+pExport3.stderr.setEncoding('utf8');
+pExport3.stderr.on('data', (data) => {
+  pExport3Stderr += data;
+});
+pExport3.on('close', mustCall((code) => {
+  assert.strictEqual(code, expectedCode);
+  assert.ok(!pExport3Stderr.includes(expectedNote),
+            `${expectedNote} must not be included in ${pExport3Stderr}`);
+}));
+
+const pImport1 = spawn(process.execPath, ['--experimental-modules', Import1]);
+let pImport1Stderr = '';
+pImport1.stderr.setEncoding('utf8');
+pImport1.stderr.on('data', (data) => {
+  pImport1Stderr += data;
+});
+pImport1.on('close', mustCall((code) => {
+  assert.strictEqual(code, expectedCode);
+  assert.ok(pImport1Stderr.includes(expectedNote),
+            `${expectedNote} not found in ${pExport1Stderr}`);
+}));
+
+// Note this test shouldn't include the note
+const pImport2 = spawn(process.execPath, ['--experimental-modules', Import2]);
+let pImport2Stderr = '';
+pImport2.stderr.setEncoding('utf8');
+pImport2.stderr.on('data', (data) => {
+  pImport2Stderr += data;
+});
+pImport2.on('close', mustCall((code) => {
+  // As this exits normally we expect 0
+  assert.strictEqual(code, 0);
+  assert.ok(!pImport2Stderr.includes(expectedNote),
+            `${expectedNote} must not be included in ${pImport2Stderr}`);
+}));
+
+const pImport3 = spawn(process.execPath, ['--experimental-modules', Import3]);
+let pImport3Stderr = '';
+pImport3.stderr.setEncoding('utf8');
+pImport3.stderr.on('data', (data) => {
+  pImport3Stderr += data;
+});
+pImport3.on('close', mustCall((code) => {
+  assert.strictEqual(code, expectedCode);
+  assert.ok(pImport3Stderr.includes(expectedNote),
+            `${expectedNote} not found in ${pImport3Stderr}`);
+}));
+
+
+const pImport4 = spawn(process.execPath, ['--experimental-modules', Import4]);
+let pImport4Stderr = '';
+pImport4.stderr.setEncoding('utf8');
+pImport4.stderr.on('data', (data) => {
+  pImport4Stderr += data;
+});
+pImport4.on('close', mustCall((code) => {
+  assert.strictEqual(code, expectedCode);
+  assert.ok(pImport4Stderr.includes(expectedNote),
+            `${expectedNote} not found in ${pImport4Stderr}`);
+}));
+
+// Must exit with zero and show note
+const pImport5 = spawn(process.execPath, ['--experimental-modules', Import5]);
+let pImport5Stderr = '';
+pImport5.stderr.setEncoding('utf8');
+pImport5.stderr.on('data', (data) => {
+  pImport5Stderr += data;
+});
+pImport5.on('close', mustCall((code) => {
+  assert.strictEqual(code, 0);
+  assert.ok(!pImport5Stderr.includes(expectedNote),
+            `${expectedNote} must not be included in ${pImport5Stderr}`);
+}));
+
+// Must exit with zero and not show note
+const pImport6 = spawn(process.execPath, [Import1]);
+let pImport6Stderr = '';
+pImport6.stderr.setEncoding('utf8');
+pImport6.stderr.on('data', (data) => {
+  pImport6Stderr += data;
+});
+pImport6.on('close', mustCall((code) => {
+  assert.strictEqual(code, expectedCode);
+  assert.ok(!pImport6Stderr.includes(expectedNote),
+            `${expectedNote} must not be included in ${pImport6Stderr}`);
+}));