Describe the bug

I want to reference libs in my layers with import { somefunc } from '@layer/somelib';.
When setting the alias build argument for esbuild, it throws an error :

const opts = {
            bundling: {
                externalModules: ['@aws-sdk/*', 'aws-lambda', '@layer/*'],
                esbuildArgs: {
                    '--alias': '@layer=',
                },
            },
        };

It will generate a bundling step like this:

esbuild --bundle src/index.js  --outfile=dist/index.js --alias=@layer=
✘ [ERROR] Invalid build flag: "--alias=@layer="

  Use "--alias:@layer=" instead of "--alias=@layer=". Flags that can be re-specified multiple times
  use ":" instead of "=".

By replacing the = with : it solves the issue

Expected Behavior

esbuildArgs key/value needs : when it can be re-specified.

Current Behavior

esbuildArgs['--alias'] is using = which leads to a bundle error.

Full stack:

    at AssetStaging.bundle (node_modules/aws-cdk-lib/core/lib/asset-staging.js:2:603)
    at AssetStaging.stageByBundling (node_modules/aws-cdk-lib/core/lib/asset-staging.js:1:4540)
    at stageThisAsset (node_modules/aws-cdk-lib/core/lib/asset-staging.js:1:1901)
    at Cache.obtain (node_modules/aws-cdk-lib/core/lib/private/cache.js:1:242)
    at new AssetStaging (node_modules/aws-cdk-lib/core/lib/asset-staging.js:1:2296)
    at new Asset (node_modules/aws-cdk-lib/aws-s3-assets/lib/asset.js:1:736)
    at AssetCode.bind (node_modules/aws-cdk-lib/aws-lambda/lib/code.js:1:4628)
    at new Function (node_modules/aws-cdk-lib/aws-lambda/lib/function.js:1:2829)
    at new NodejsFunction (node_modules/aws-cdk-lib/aws-lambda-nodejs/lib/function.js:1:1171)
    at new MyConstruct (stack/MyConstruct .ts:18:9)

Reproduction Steps

CDK:

new NodejsFunction(this, 'test-function', {
            entry: 'src/functions/test/index.ts',
            architecture: Architecture.ARM_64,
            runtime: Runtime.NODEJS_18_X,
            memorySize: 128,
            tracing: Tracing.ACTIVE,
            handler: 'index.handler',
            timeout: Duration.seconds(30),
            retryAttempts: 0,
            logRetention: RetentionDays.ONE_DAY,
            bundling: {
                minify: process.env.NODE_ENV === 'production',
                banner: 'import { createRequire } from \'module\'; const require = createRequire(import.meta.url);',
                mainFields: ['module', 'main'],
                target: 'node18',
                externalModules: ['@aws-sdk/*', 'aws-lambda', '@layer/*'],
                esbuildArgs: {
                    '--alias': '@layer=',
                },
                format: OutputFormat.ESM,
            },
        });

Lambda

// src/functions/test/index.ts
import { ping } from '@layer/echo';

Layer

// dist/layers/echo/index.js
export{console.log as ping};

Possible Solution

esbuildArgs key/value needs : when it can be re-specified; from documentation:

CLI: If you are using the command-line API, it may be helpful to know that the flags come in one of three forms: --foo, --foo=bar, or --foo:bar. The form --foo is used for enabling boolean flags such as --minify, the form --foo=bar is used for flags that have a single value and are only specified once such as --platform=, and the form --foo:bar is used for flags that have multiple values and can be re-specified multiple times such as --external:.

Additional Information/Context

No response

CDK CLI Version

2.76.0 (build 78c411b)

Framework Version

No response

Node.js Version

Node.js v19.8.1

OS

WSL2 Ubuntu

Language

Typescript

Language Version

Typescript (5.0.4)

Other information

No response