New exports break TypeScript "bundler" compilation

[pfumagalli]

node-postgres/packages/pg-protocol/package.json

Lines 7 to 18 in 9bfc967

	"exports": {
	".": {
	"import": "./esm/index.js",
	"require": "./dist/index.js",
	"default": "./dist/index.js"
	},
	"./dist/*": {
	"import": "./dist/*",
	"require": "./dist/*",
	"default": "./dist/*"
	}
	},

It seems that by adding the new "exports" flags to package.json, now when compiling anything depending on pg (and relatively @types/pg) using the bundler module resolution fails with:

│ /home/runner/work/lib-sqs/lib-sqs/node_modules/@types/pg/index.d.ts
│   12:31  Cannot find module 'pg-protocol/dist/messages' or its corresponding type declarations. [TS2307]
│          | import { NoticeMessage } from 'pg-protocol/dist/messages';

I think the correct definition for the dist export in package.json should be something like the following:

"exports": {
  ".": {
    "import": "./esm/index.js",
    "types": "./dist/index.d.ts",
    "require": "./dist/index.js",
    "default": "./dist/index.js"
  },
  "./dist/*": {
    "types": "./dist/*.d.ts",
    "require": "./dist/*.js"
  }
}

Nothing in dist seems to be an ESM module (so no "import") and types and extensions should be explicit...

[brianc]

ah okay thanks for that report and thanks for the suggested changes! Any idea how I could repro this locally so I can test my fix works? Otherwise i'll just be kinda blindly publishing changes to npm hoping it fixes your issue.

[pfumagalli]

Upon further inspection, this might not be a bug in pg-protocolo but rather in the plethora of cross dependencies between all pg packages and related.

Spent some time to try and find a minimal reproduction (wasn't easy). It stems from here:

getsentry/sentry-javascript#16196

Now, it seems that @sentry/node imports @opentelemetry/instrumentation-pg@0.51.1, and that imports:

• @types/pg@8.6.1 (old version)
• @types/pg-pool@2.0.6 which imports @types/pg@8.11.14 (it's declared as * but NPM resolves to the latest)

To cut the story short, the problem is when an older version of the @types/pg (pre 8.11) is imported somewhere in the tree.

Version 8.10.9 of @types/pg imports simply the following:

import { NoticeMessage } from "pg-protocol/dist/messages";

rather than the newer:

import { NoticeMessage } from "pg-protocol/dist/messages.js";

Without the new exports field TypeScript was free to resolve all sorts of stuff and it somehow found the types, with when this was introduced, it now behaves a lot more strictly, and can't ultimately resolve the messages.d.ts file.

And given that dependencies to pg-protocol are associated with the * version, and this breaking change happened in a minor version, NPM gets lost, dedupes what it shouldn't, and the whole thing falls over!

The above changes definitely fix the problem for now but I wouldn't know if they will introduce some issues in the future.

I'd say that if anyone stumbles on this issue, they should make sure that there are no pre-8.11 versions of @types/pg in their tree or (as I did) should locally declare a dependency to pg-protocol to a version <1.9.

The minimal repro is attached. Basically, a simple package with two dependencies:

    "@types/pg": "<8.11"
    "pg": "<8.11"

makes compilation fail in bundler, nodenext and possibly other modes.

Here's the zip file.