Broken output with "--bundle-node-modules" option

[jls-tschanzc]

Env:

"dependencies": {
  "aws-sdk": "2.585.0"
},
"externals": {
  "aws-sdk": "aws-sdk"
},
"devDependencies": {
  "@types/aws-lambda": "^8.10.47",
  "@types/node": "^13.9.8",
  "parcel-bundler": "^1.12.4",
  "parcel-plugin-externals": "^0.3.3-pre.20200323.2",
  "typescript": "^3.8.3"
},
"engines": {
  "node": ">=12.0.0 <13.0.0"
}

Code written in Typescript.

What I wanted to achieve:

Generally bundle all node_modules except a few external ones ("aws-sdk" for a lambda in my case).

Problem I encountered:

My index.ts looks something like this:

import { Handler } from 'aws-lambda'; // Types only "@types/aws-lambda" in devDependencies
import { Athena } from 'aws-sdk';
import { format } from 'util';
// Other code imports local to src folder [...]

export const handler: Handler = async (event, context) => {
  const athenaService = new Athena();

  //...

  return format('%s Done', 'Really');
};

When I compile this normally with e.g. parcel build ./src/index.ts --out-dir dist --out-file index.js --global handler --target=node --experimental-scope-hoisting --no-source-maps --no-content-hash it works correctly and the require('aws-sdk') is correctly left in the output.

But if I compile it with the --bundle-node-modules it breaks and the output contains something like this:

var k={};k=aws-sdk;

also the parcel output shows:

dist/index.js                                1.33 KB    1.38s
dist/aws-sdk => aws-sdk.5848e953.external        0 B     26ms

In both cases the require('util') is present in the output as it should.

[FlorianRappl]

Sounds reasonable. I'll investigate!

[jls-tschanzc]

Forgot to post my tsconfig, thanks for checking :)

{
  "compilerOptions": {
    "target": "ES2018",
    "module": "commonjs",
    "lib": ["ES2018"],
    "sourceMap": false,
    "outDir": "./dist",
    "strict": true,
    "noImplicitAny": true,
    "baseUrl": "./src",
    "typeRoots": ["node_modules/@types"],
    "types": ["node"],
    "esModuleInterop": true,
    "inlineSourceMap": false,
    "resolveJsonModule": true,
    "forceConsistentCasingInFileNames": true
  }
}

[FlorianRappl]

Alright so I looked into this and the behavior is not a bug.

The following things appear:

1. You use target=node, which - by default - does not bundle in any modules. So the plugin is not even active.
2. You use bundle-node-modules, which activates the plugin - however, you use as rule "aws-sdk": "aws-sdk", which - in the string array mode - would translate to "aws-sdk => aws-sdk". Obviously, this is not what is desired. Potentially this is a confusion with "react": "React". In this case a global variable React would be used instead of require('react').

For an existing module you'd still want require("aws-sdk"). So you now have 2 options.

1. Just use "aws-sdk => require('aws-sdk')
2. Go to the string array version

"dependencies": {
  "aws-sdk": "2.585.0"
},
"externals": [
  "aws-sdk"
],
"devDependencies": {
  "@types/aws-lambda": "^8.10.47",
  "@types/node": "^13.9.8",
  "parcel-bundler": "^1.12.4",
  "parcel-plugin-externals": "^0.3.3-pre.20200323.2",
  "typescript": "^3.8.3"
},
"engines": {
  "node": ">=12.0.0 <13.0.0"
}

Hope that helps!

[jls-tschanzc]

Thanks @FlorianRappl for taking the time to check this, but sadly your proposed way does not work. When I set:

  "externals": [
    "aws-sdk"
  ],

or

  "externals": [
    "aws-sdk => require('aws-sdk')"
  ],

parcel will fail:

> parcel build ./src/index.ts --out-dir dist --out-file index.js --global handler --target=node --experimental-scope-hoisting --no-source-maps --no-content-hash --bundle-node-modules

🚨  /aws-sdk.external:1:23: Cannot resolve dependency 'aws-sdk'
    at Resolver.resolve (node_modules/parcel-bundler/src/Resolver.js:71:17)
    at async Bundler.resolveAsset (node_modules/parcel-bundler/src/Bundler.js:433:18)
    at async Bundler.resolveDep (node_modules/parcel-bundler/src/Bundler.js:484:14)
    at async node_modules/parcel-bundler/src/Bundler.js:608:26
    at async Promise.all (index 1)
    at async Bundler.loadAsset (node_modules/parcel-bundler/src/Bundler.js:599:21)
    at async node_modules/parcel-bundler/src/Bundler.js:610:13
    at async Promise.all (index 2)
    at async Bundler.loadAsset (node_modules/parcel-bundler/src/Bundler.js:599:21)
    at async Bundler.processAsset (node_modules/parcel-bundler/src/Bundler.js:557:5)

[FlorianRappl]

It works for me - sure you, e.g., installed aws-sdk?

Keep in mind that the package must exist - externals just means that it will not be bundled in.

[jls-tschanzc]

After a bit more testing I found the issue to be the --experimental-scope-hoisting parcel option. When using the build command (e.g.):

parcel build ./src/index.ts --out-dir dist --out-file index.js --global handler --target=node --bundle-node-modules --no-minify --experimental-scope-hoisting 

it will fail as I described in my last comment but without using the scope-hoisting:

parcel build ./src/index.ts --out-dir dist --out-file index.js --global handler --target=node --bundle-node-modules --no-minify

it works as you said. Sadly this leads to an increased final bundle size.

[FlorianRappl]

Yeah good point. Not sure yet if its something about this configuration or in general.

Note that parcel's scope hoisting option is experimental and that parcel does not make a guarantee on its correctness (as a matter of fact it sometimes misses important stuff).