switch to esm-only with development condition enabling dev-instanceOf-check

[yaacovCR]

Takes the no-op trick from #4426, but responding in a small way to feedback from @glasser in terms of discoverability, uses the development condition to enable this behavior by default.

The development condition must be passed to node via a flag node --conditions=development ... and is not set automatically from NODE_ENV=development.

[yaacovCR]

where we get the import-only warning, we are actually relying on esm-require

[glasser]

For what it's worth, I do think this will hinder adoption due to popular testing libraries like Jest still having pretty terrible support for using ESM-only modules even when Node and TypeScript are in better shape. While I think graphql-js should go here eventually, it will be disappointing if 3+ years worth of incremental improvements are made inaccessible to users who don't want to fight with their test tooling. I think it would be better to get out a GraphQL v17 that has the huge number of small improvements (but no major changes to the build system, implementation of dev mode, etc) and then rapidly release a GraphQL v18 that ONLY has these "build level" changes, so that users can separate their "application-level" migration from their "build system" migration.

[yaacovCR]

The underlying motivation is that require-esm supposedly “just works” in the latest versions of Node, so that our users using Jest would not be impacted.

I hope to push another alpha to allow the broader community to experiment with it.

[glasser]

I encourage you to try it out yourself. I tried making a simple package (@as-integrations/express4) ESM-only and found that it worked great when run directly from a Node CJS project but that trying to get it to work with Jest (while the project was still CJS-based) was hopeless.