(node: @aws-cdk/region-info): using latest version of @aws-cdk/region-info throws an "Cannot find module 'aws-cdk-lib/core/lib/errors'" error

[eduardomourar]

Describe the bug

This already has been reported in issue #34690.

While using @aws-cdk/region-info v2.232.2, we get this error:

Error: Cannot find module 'aws-cdk-lib/core/lib/errors'

Regression Issue

• Select this option if this issue appears to be a regression.

Last Known Working CDK Library Version

2.199.0

Expected Behavior

That it doesn't crash on use.

Current Behavior

It crashes completely due to not being able to find a module.

Reproduction Steps

package.json

{
  "name": "aws-testing",
  "version": "1.0.0",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "",
  "license": "N/A",
  "description": "",
  "dependencies": {
    "@aws-cdk/region-info": "^2.232.2"
  }
}

Simple code:

const { Fact, FactName } = require("@aws-cdk/region-info");

const isValidRegion = (region) => {
    const myRegion = Fact.find(region, FactName.DOMAIN_SUFFIX);
    return myRegion !== undefined && myRegion !== null;
}

(() => {
    console.log(isValidRegion("eu-west-1"));
})();

Using latest version results in the error I mentioned, if you use version 2.199.0 then this script works and returns true.

Possible Solution

Either replace the UnscopedValidationError with Error instance or publish the error classes as a library to each package management.

Additional Information/Context

No response

AWS CDK Library version (aws-cdk-lib)

2.232.2

AWS CDK CLI version

2.232.2

Node.js Version

22.21.1

OS

MacOS 26.0.1

Language

TypeScript

Language Version

No response

Other information

I have not confirmed it, but I assume the same error will affect @aws-cdk/cx-api.

[pahud]

Hi @eduardomourar,

Thank you for reporting this issue. You're correct that this appears to be the same underlying problem as #34690.

The previous fix in PR #34691 exported errors.js from aws-cdk-lib, but it didn't address the fundamental issue: @aws-cdk/region-info imports from aws-cdk-lib at runtime, yet aws-cdk-lib is only listed as a devDependency in the package.json.

The root cause traces back to PR #33384, which changed the package to use UnscopedValidationError instead of plain Error instances. This introduced a runtime dependency on aws-cdk-lib that wasn't properly declared.

As a workaround, use aws-cdk-lib/region-info directly instead

If you're already using aws-cdk-lib, just import from there:

const { Fact, FactName } = require("aws-cdk-lib/region-info");

Since @mrgrain has self-assigned this issue, we'll defer to their expertise on the best approach forward.

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