chore(lambda-nodejs): update default runtime (aws#13664)

If the installed node version is >= 14, use Node.js 14.x. Otherwise, use
Node.js 12.x.

This removes a default on the deprecated Node.js 10.x runtime.

BREAKING CHANGE: the default runtime of a `NodejsFunction` is now Node.js 14.x if the environment from which it is deployed uses Node.js >= 14 and Node.js 12.x otherwise.


----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

packages/@aws-cdk/aws-lambda-nodejs/lib/function.ts

@@ -34,8 +34,8 @@ export interface NodejsFunctionProps extends lambda.FunctionOptions {
    * The runtime environment. Only runtimes of the Node.js family are
    * supported.
    *
-   * @default - `NODEJS_12_X` if `process.versions.node` >= '12.0.0',
-   * `NODEJS_10_X` otherwise.
+   * @default - `NODEJS_14_X` if `process.versions.node` >= '14.0.0',
+   * `NODEJS_12_X` otherwise.
    */
   readonly runtime?: lambda.Runtime;
 
@@ -105,9 +105,9 @@ export class NodejsFunction extends lambda.Function {
     // Entry and defaults
     const entry = path.resolve(findEntry(id, props.entry));
     const handler = props.handler ?? 'handler';
-    const defaultRunTime = nodeMajorVersion() >= 12
-      ? lambda.Runtime.NODEJS_12_X
-      : lambda.Runtime.NODEJS_10_X;
+    const defaultRunTime = nodeMajorVersion() >= 14
+      ? lambda.Runtime.NODEJS_14_X
+      : lambda.Runtime.NODEJS_12_X;
     const runtime = props.runtime ?? defaultRunTime;
 
     super(scope, id, {

packages/@aws-cdk/aws-lambda-nodejs/test/function.test.ts

@@ -7,6 +7,7 @@ import { Runtime } from '@aws-cdk/aws-lambda';
 import { Stack } from '@aws-cdk/core';
 import { NodejsFunction } from '../lib';
 import { Bundling } from '../lib/bundling';
+import { nodeMajorVersion } from '../lib/util';
 
 jest.mock('../lib/bundling', () => {
   return {
@@ -35,8 +36,13 @@ test('NodejsFunction with .ts handler', () => {
     entry: expect.stringContaining('function.test.handler1.ts'), // Automatically finds .ts handler file
   }));
 
+  const runtime = nodeMajorVersion() >= 14
+    ? Runtime.NODEJS_14_X
+    : Runtime.NODEJS_12_X;
+
   expect(stack).toHaveResource('AWS::Lambda::Function', {
     Handler: 'index.handler',
+    Runtime: runtime.name,
   });
 });