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Enable "useDefineForClassFields" in tsc --init #39311
Description
Search Terms
useDefineForClassFields, tsc --init, tsconfig
Suggestion
tsc --init's generated tsconfig.json should include "useDefineForClassFields": true
Use Cases
All major web and non-web engines now ship Define-style semantics.
So the safest approach is to ensure new TypeScript projects use standard web-compatible behavior.
Examples
It looks like we just need to add one line here. I am happy to send a PR.
Checklist
My suggestion meets these guidelines:
- This wouldn't be a breaking change in existing TypeScript/JavaScript code
- This wouldn't change the runtime behavior of existing JavaScript code
- This could be implemented without emitting different JS based on the types of the expressions
- This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, etc.)
- This feature would agree with the rest of TypeScript's Design Goals.
Activity
RyanCavanaugh commentedon Jun 29, 2020
I think this is a good idea. Anders Hejlsberg (@ahejlsberg) Daniel Rosenwasser (@DanielRosenwasser) thoughts?
Enable "useDefineForClassFields" in tsc --init
sandersn commentedon Jul 2, 2020
Three concerns we should discuss:
[[Set]]and[[Define]]differences are observable.[[Define]]semantics are at stage 3, so strict standards compliance isn't really a motivator yet.We have existing features with non-compliant emit, iteration for example, and errors to prevent the non-compliance from being observed, so there's precedence for prioritising good emit over standards compliance.
If we had multiple
--initoptions, this would be the perfect addition to a "latest" init.orta commentedon Jul 5, 2020
I added it to the recommended tsconfig base: tsconfig/bases#15
sandersn commentedon Sep 18, 2020
From discussion in the design meeting: We decided not to do this until
[[Define]]semantics ship in some ES20xx spec, and that ES20xx becomes the default target intsc --init.Currently the default target is ES5, which we need to rethink -- in my opinion, ES2015 at least should be the default.