serverless · krkcode60 · Aug 30, 2022 · Aug 31, 2022
diff --git a/lib/plugins/aws/invoke-local/index.js b/lib/plugins/aws/invoke-local/index.js
@@ -842,10 +842,18 @@ class AwsInvokeLocal {
           pathToHandler = `${pathToHandler}.cjs`;
           try {
             return require(pathToHandler);
-          } catch (innerError) {
-            // Throw original error if still "MODULE_NOT_FOUND", as not finding module with `.cjs` might be confusing
-            if (innerError.code !== 'MODULE_NOT_FOUND') {
-              throw innerError;
+          } catch (cjsInnerError) {
+            if (cjsInnerError.code !== 'MODULE_NOT_FOUND') {
+              throw cjsInnerError;
+            }
+            // Attempt to load `.mjs` extension
+            try {
+              return await import(`file:///${modulePath}.mjs`);
+            } catch (mjsInnerError) {
+              if (mjsInnerError.code !== 'MODULE_NOT_FOUND') {
+                throw mjsInnerError;
+                // Throw original error if still "MODULE_NOT_FOUND", as not finding module with `.cjs` might be confusing
+              }
             }
           }
         }

diff --git a/package.json b/package.json
@@ -120,6 +120,15 @@
           "no-console": "off"
         }
       },
+      {
+        "files": [
+          "test/fixtures/programmatic/invocation/cjs/**"
+        ],
+        "parserOptions": {
+          "sourceType": "module",
+          "allowImportExportEverywhere": true
+        }
+      },
       {
         "files": [
           "test/fixtures/programmatic/plugin/local-esm-plugin/**",

diff --git a/test/fixtures/programmatic/invocation/cjs/async-esm-mjs-in-commonjs-package-type.mjs b/test/fixtures/programmatic/invocation/cjs/async-esm-mjs-in-commonjs-package-type.mjs
@@ -0,0 +1,14 @@
+export const handler = async (event, context) => {
+  if (event && event.shouldFail) throw new Error('Failed on request');
+  return {
+    statusCode: 200,
+    body: JSON.stringify({
+      message: 'Invoked',
+      event,
+      clientContext: context.clientContext,
+      env: process.env,
+    }),
+  };
+};
+
+export default handler;
diff --git a/test/fixtures/programmatic/invocation/cjs/package.json b/test/fixtures/programmatic/invocation/cjs/package.json
@@ -0,0 +1,3 @@
+{
+  "type": "commonjs"
+}
diff --git a/test/fixtures/programmatic/invocation/esm/async-esm-mjs-in-module-package-type.mjs b/test/fixtures/programmatic/invocation/esm/async-esm-mjs-in-module-package-type.mjs
@@ -0,0 +1,14 @@
+export const handler = async (event, context) => {
+  if (event && event.shouldFail) throw new Error('Failed on request');
+  return {
+    statusCode: 200,
+    body: JSON.stringify({
+      message: 'Invoked',
+      event,
+      clientContext: context.clientContext,
+      env: process.env,
+    }),
+  };
+};
+
+export default handler;
diff --git a/test/fixtures/programmatic/invocation/serverless.yml b/test/fixtures/programmatic/invocation/serverless.yml
@@ -16,6 +16,10 @@ functions:
     handler: async-cjs.handler
   asyncEsm:
     handler: esm/async-esm.handler
+  asyncEsmMjsInModulePackageType:
+    handler: esm/async-esm-mjs-in-module-package-type.handler
+  asyncEsmMjsInCommonjsPackageType:
+    handler: cjs/async-esm-mjs-in-commonjs-package-type.handler
   contextDone:
     handler: context-done.handler
   contextSucceed:

diff --git a/test/unit/lib/plugins/aws/invoke-local/index.test.js b/test/unit/lib/plugins/aws/invoke-local/index.test.js
@@ -1192,6 +1192,24 @@ describe('test/unit/lib/plugins/aws/invokeLocal/index.test.js', () => {
         options: { function: 'asyncEsm' },
       });
 
+      expect(output).to.include('Invoked');
+    });
+    it('should support loading handlers that are ES modules with `.mjs` extension in packages of `module` type', async () => {
+      const { output } = await runServerless({
+        fixture: 'invocation',
+        command: 'invoke local',
+        options: { function: 'asyncEsmMjsInModulePackageType' },
+      });
+
+      expect(output).to.include('Invoked');
+    });
+    it('should support loading handlers that are ES modules with `.mjs` extension in packages of `commonjs` type', async () => {
+      const { output } = await runServerless({
+        fixture: 'invocation',
+        command: 'invoke local',
+        options: { function: 'asyncEsmMjsInCommonjsPackageType' },
+      });
+
       expect(output).to.include('Invoked');
     });
   });