What

Reproduction of an issue with Custom Conditions.

Problem

While BWIP-JS's export map is used by vite for module resolution (if you set resolve.browserField to false like in app's vite config), Typescript/tsc doesn't allow for cascading custom conditions.

As an example of the usecases, my team has a rendering abstraction for shapes. It's kind of like BWIP-JS's DrawingContext interface, since it lets us define label objects using shape primitives. For barcodes, we have a DrawingContext implementation that wraps our rendering abstraction.

The upside is that BWIP-JS doesn't need to know if we're rendering to an SVG or to a PDF. The downside is that BWIP-JS doesn't know if we're rendering to an SVG or to a PDF...

The determining factor for the exports map resolution is whether the rendering library is being imported in the application for a preview (SVG), or in the print-time renderer on the backend (PDF).

This was all well and good until I decided to try to migrate our Typescript codebase from using "moduleResolution": "Node" to "moduleResolution": "Bundler".

The conditions that tsc uses for exports map resolution are import and types, when moduleResolution is set to "Bundler". When moduleResolution is set to "Node", the exports map isn't even consulted. Instead, the main and browser fields are used (which explains why it worked before changing moduleResolution).

This made it impossible for Typescript to determine which type declaration file to resolve, which therefore broke our linting.