Type error between Angular CLI and Browserslist when extending a browserslist config

[maharielrosario]

Command

build

Is this a regression?

• Yes, this behavior used to work in the previous version

The previous version in which this bug was not present was

No response

Description

I have a fresh Angular 19 application and I am trying to extend a browserslist configuration from a TS library that I changed to JS while debugging this issue. When I run the Angular build, it throws a type error.

Originally, I opened a ticket with the browserslist team so you can see browserslist/browserslist#891 for further context. I was getting errors with browserslist as they are using CommonJS requires in their code and my library and app were ESM. After removing browserslist-useragent-regexp, simplifying my library to JS, and still getting errors, they asked me to reach out to Angular as they were thinking Angular had an over complicated environment.

Minimal Reproduction

Create a shareable config following browserslist's instructions here: https://github.com/browserslist/browserslist?tab=readme-ov-file#shareable-configs

Here is my particular example with text changed as it's for a client I'm working with:

Snippet of application's package.json:

  "type": "module",
  "browserslist": [
    "extends @scope/browserslist-config-xxxx"
  ]

Here is the library's code for this config:

index.js

const BROWSERSLIST_QUERY = ['defaults'];
export default BROWSERSLIST_QUERY;

snippet of package.json

  "type": "module",
  "browserslist": [
    "extends @scope/browserslist-config-xxxx"
  ]

Exception or Error

[error] TypeError: Cannot read properties of undefined (reading 'length')
    at find (/../node_modules/browserslist/parse.js:12:25)
    at matchBlock (/../node_modules/browserslist/parse.js:46:10)
    at /../node_modules/browserslist/parse.js:73:17
    at Array.map (<anonymous>)
    at parse (/../node_modules/browserslist/parse.js:70:13)
    at parseQueries (/../node_modules/browserslist/index.js:454:16)
    at resolve (/../node_modules/browserslist/index.js:322:10)
    at Function.select (/../node_modules/browserslist/index.js:1163:14)
    at /../node_modules/browserslist/index.js:332:29
    at Array.reduce (<anonymous>)

Your Environment

Angular CLI: 19.2.8
Node: 22.14.0
Package Manager: npm 10.9.2
OS: darwin arm64

Angular: 19.2.7
... common, compiler, compiler-cli, core, forms
... platform-browser, platform-browser-dynamic, router

Package                         Version
---------------------------------------------------------
@angular-devkit/architect       0.1902.8
@angular-devkit/build-angular   19.2.8
@angular-devkit/core            19.2.8
@angular-devkit/schematics      19.2.8
@angular/cli                    19.2.8
@schematics/angular             19.2.8
rxjs                            7.8.2
typescript                      5.7.3
zone.js                         0.15.0

Anything else relevant?

No response