only one instance of babel-polyfill is allowed

[Gerst20051]

Serverless plugin "serverless-dynalite" initialization errored: only one instance of babel-polyfill is allowed

[Gerst20051]

I'm writing this 4 months after looking through this issue so some things may be incorrect but want to write down my thoughts as I remember them...

I think the root cause is when multiple packages require the package require("babel-polyfill");.

The two packages in my case were serverless-dynalite and @serverless/platform-sdk.

This issue started popping up after serverless version 1.28.0 which started including the @serverless/platform-sdk dependency.

See here: serverless/serverless@v1.27.3...v1.28.0#diff-b9cfc7f2cdf78a7f4b91a753d10865a2R95

Inside that dependency, you'll find the following line which also requires the package require("babel-polyfill");.

You can see that line in the @serverless/platform-sdk package here: https://github.com/serverless/platform-sdk/blob/master/src/index.js#L2-L5

if (!global._babelPolyfill) {
  require('babel-polyfill')
}

You can also see that line in the serverless-dynalite package here:

serverless-dynalite/index.js

Line 3 in 5883f8a

require("babel-polyfill");

require("babel-polyfill");

The major difference is that serverless-dynalite doesn't do the if (!global._babelPolyfill) { check.

THE FIX:

This issue was encountered in two different ways and it was fixed differently in both cases. You could also clone/fork this repo and add that check above that is missing.

The first was when running sls deploy in gitlab pipelines.

• This was fixed by updating .gitlab-ci.yml to use the version of serverless from the project's node_modules folder by changing sls deploy to npm run sls deploy.

• The command npm run sls references the script "sls": "npx serverless" in package.json.

• The version of serverless didn't seem to make a difference in this instance since this is what was defined in the package.json "serverless": "^1.30.3",.

• This might be because the serverless-dynalite module is included first or doesn't get bundled when deploying? Might be completely wrong on that though...

The second was when running serverless (npx serverless offline) locally.

• The latest version of serverless that works is version "1.27.3".

• There was an update mentioned above in version "1.28.0" that started causing this error. That update "broke" versions "1.28.0" through "1.30.3".

• I haven't checked versions "1.30.3" through "1.35.1".