Does it make sense to allow `module: nodenext` + `moduleResolution: node`?

[DanielRosenwasser]

In #48835, a user ran into an issue where the combined options were questionable. It seems like an innocent mistake, and by all means moduleResolution: node sounds compatible with module: nodenext or moduleResolution: node.

Should we issue an error in some of these cases?

CC @weswigham @andrewbranch

[weswigham]

So it is technically a useful configuration - we won't detect any esm files (since the resolution mode is pre-esm), but we will use the new cjs transform (ie, leaving dynamic import alone) on all the input modules.

[craigphicks]

To make a long story short

module	moduleResolution	uses package.json:type
unset	"node12"	true
"node12"	unset	true
"node12"	"node"	false

If you had a simple table like that (possibly with more entries) next to the documentation for both module and moduleResolution, I think it would prevent unnecessary confusion.

That is apart from the question of whether that combination should be allowed

[magicdawn]

the moduleResolution option naming is bad, classic & node is well documented on page https://www.typescriptlang.org/docs/handbook/module-resolution.html

but not node12/nodenext(now node16/nodenext), and not updated on tsconfig reference page

the node12 / node16 / nodenext should be renamed to node-esm and points a link to the Node.js ESM resolve spec https://nodejs.org/dist/latest-v16.x/docs/api/esm.html#resolver-algorithm-specification

[andrewbranch]

Strongly disagree. The TSConfig reference docs should change. node16/nodenext is the only correct module resolution option if you are targeting Node 16+ (really 12+ with some caveats about async/await and certain package.json exports features). node16/nodenext do not imply that everything uses ESM resolution; they simply correspond to versions of Node where ESM is available side-by-side with CJS. The resolution algorithm switches between CJS (more or less what you get all the time in --moduleResolution node) and Node’s new ESM resolver algorithm based on the input type that Node will see for the given import, which varies based on package.json type, file extension, and import syntax. Even if you are using exclusively CJS source and dependencies in Node 12+, using --moduleResolution node would be incorrect because it doesn’t respect package.json exports, while CJS resolution in Node 12+ does. Eventually, I would like to rename node to something that implies it’s only suitable for legacy code.