microsoft / microsoft/TypeScript

Object.values and Object.entries are unsound and inconsistent with Object.keys.

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Description

Search Terms:
Object.values Object.entries sound soundness unsound inconsistent Object.keys

Code
Proposed change: https://github.com/MicahZoltu/TypeScript/commit/603c36370c7fdcd142b1493ca8cbbb955db73b69

Related Issues:
#12207
#12253

Back in November 2016, a PR (#12207) was submitted to make the types of Object.entries and Object.values generic. This PR was reviewed and accepted, and as a note it was recommended that Object.keys be updated similarly. The author then submitted a PR to update Object.keys (#12253) but @ahejlsberg made the very valid point that this change was unsound and the PR was closed. The author of both PRs then suggested that perhaps #12207 should be reverted, but this revert never happened.

This issue is to discuss options for rectifying this situation and I propose we make Object.entries and Object.values consistent with the sound behavior of Object.keys. The major issue here is that this IS a breaking change since people may be relying on the currently unsound behavior of Object.values and Object.entries. However, I think having TypeScript be inconsistent on this front indefinitely is not good, and I don't think changing Object.keys to be unsound is the right solution, so at the least this change should be merged into TS 4.x.

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

No source files, tests, or entry points are identified in the issue. Start by reading the proposed commit, related issues #12207 and #12253, and the discussion about soundness and breaking changes. Done means the project has agreed on a concrete, consistent behavior for Object.values and Object.entries.

Written by the indexing model from the issue text.

Assessment

Tech stack
typescript
Domain
compilers
Issue type
Bug
Difficulty
5/5
Estimated time
Over a week
Activity status
Quiet
Clarity
Needs clarification
Newbie friendliness
35/100

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