New exports condition breaks require('pg/lib/type-overrides')

[mmkal]

Hi! I got a bug report in pgkit which uses pg/lib/type-overrides: mmkal/pgkit#443

It seems to be because of the new exports definition on package.json

Here's an easy repro you can run in another project (empty directory after npm init -y, say):

npm i pg@~8.14.0 && node -e "require('pg/lib/type-overrides')" # succeeds
npm i pg@~8.15.0 && node -e "require('pg/lib/type-overrides')" # fails
npm i pg@~8.16.0 && node -e "require('pg/lib/type-overrides')" # fails

Error for the latter two looks like:

Error: Cannot find module '/Users/mmkal/src/scratch/node_modules/pg/lib/type-overrides'
    at createEsmNotFoundErr (node:internal/modules/cjs/loader:1441:15)
    at finalizeEsmResolution (node:internal/modules/cjs/loader:1430:15)
    at resolveExports (node:internal/modules/cjs/loader:661:14)
    at Function._findPath (node:internal/modules/cjs/loader:753:31)
    at Function._resolveFilename (node:internal/modules/cjs/loader:1391:27)
    at defaultResolveImpl (node:internal/modules/cjs/loader:1061:19)
    at resolveForCJSWithHooks (node:internal/modules/cjs/loader:1066:22)
    at Function._load (node:internal/modules/cjs/loader:1215:37)
    at TracingChannel.traceSync (node:diagnostics_channel:322:14)
    at wrapModuleLoad (node:internal/modules/cjs/loader:235:24) {
  code: 'MODULE_NOT_FOUND',
  path: '/Users/mmkal/src/scratch/node_modules/pg'
}

If you go into node_modules and delete the exports prop on package.json, it works ok again.

It also works if you add ./lib/type-overrides explicitly, so one option might be to explicitly write out every supported import like this:

  "exports": {
    ".": {
      "import": "./esm/index.mjs",
      "require": "./lib/index.js",
      "default": "./lib/index.js"
    },
    "./lib/type-overrides": {
      "import": "./esm/type-overrides.mjs",
      "require": "./lib/type-overrides.js",
      "default": "./lib/type-overrides.js"
    },
    "./lib/*": {
      "import": "./lib/*",
      "require": "./lib/*",
      "default": "./lib/*"
    }
  },

Possibly related to #3457 but arguably this is more serious since it affects runtime.

[pmalouin]

We're also affected by this issue.

It looks like the fix in #3428 solved the same issue just for extensioned require()s like require('pg/lib/type-overrides.js'), but not for extensionless expressions like require('pg/lib/type-overrides').

Sharing some of my findings while tinkering...

I noticed that adding .js at the end of the exports fixes calls to require('pg/lib/type-overrides'):

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

...but that breaks support for extensioned paths, so to maintain compatibility you'd also need two entries like:

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

As an aside, I think this can actually be simplified to:

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