Design Meeting Notes, 12/3/2024

[DanielRosenwasser]

New --module Targets for Node.js

#60589
#60534

• Previously, we were pretty loose about JSON imports in nodenext.
  • We need to stop allowing named imports from these JSON files.
  • Also, Node.js requires you to use import attributes for JSON files.
• In 5.7 we added fixes for cases when we resolve to JSON files.
• We enabled this for node16 as well, but we error saying that you can only use import attributes in nodenext.
• In Node.js 16, you can only use import assertions (the old deprecated thing), not import attributes.
  • We will probably make things loose again in node16 as well - no checks for JSON modules.
• Node.js 16 is already EOL.
• So where does this leave us?
  • Node.js 18 is still in maintenance, but does support import attributes.
  • Node 23 will have require(ESM) support.
• Proposal:
  • --module nodenext allows require(ESM) (for Node.js 23/24, possibly 22)
    • Eventually settle on a specific line.
  • --module node20 depending on if the above features get back-ported.
  • --module node18 for import assertions and JSON import checks (what nodenext should be in TypeScript 5.7)
  • --module node16 to be deprecated farther down.
    • It is not the most ideal state (it is EOL, doesn't support JSON imports correctly), but TBD.
• We like this plan, we feel okay to move forward with this for TypeScript 5.8.