Use Case

downlevel-dts removes newer typescript features from type definitions without compromising their meaning. You can add a version specification in your package.json that will make older typescript versions pick up the older definitions, and latest typescript can use the unmodified types.

Dependencies

• downlevel-dts

Unknowns

• The minimum version that downlevel-dts can make our definitions compatible with.
  • Some features are too new to send back very far. 
  • Can't go further back than TypeScript 3.4.

Acceptance Criteria

Implementation Requirements

• downlevel-dts must run on prepare so that the generated defintions go into the release
• change the files property in package.json to pick up the new defintions
• builds should fail if downlevel-dts can't downlevel to any of the target versions of TypeScript.
• If possible, try to match the community types version.

Testing Requirements

Documentation Requirements

• Mention that users need to use at least x TypeScript version to make use of. This should be mentioned in the repo README/CONTRIBUTING (wherever seems most appropriate) as well as the 

  Follow Up Requirements

• Create or find a ticket that captures including a support matrix in our repo documentation.