Downgrade Build

Duplicates your project, locking your dependencies to their minimums, and tries to build it.

Usage

Adding this package to your devDependencies will give you access to a downgrade-build binary, which you can call from any npm script.

It will duplicate your project, with mutated dependencies, and run npm install, then npm run with whatever parameters you passed to the script. For many projects, you'll either want to run downgrade-build build or downgrade-build test. If you need to run more than one script, chain them together in a new script.

Motivation

With any kind of open version specification for dependencies, we risk breaking when we use features that only exist in new versions but don't bump our spec.

This utility will attempt to install and build your package with the lowest versions that are compatible, helping you to keep as wide as possible a dependency spec.

Implementation

We use ignore to avoid copying files that aren't part of your repository, and also don't copy node_modules, .git, or package-lock.json, even if they're not found at top level.

Unfortunately, none of the globbing libraries I could find actually manage to work with .gitignore files in superdirectories or subdirectories. So I wrote my own, which exposes an async generator.

Once we have a clean project in a temporary directory, we can run npm install on it.