microsoft / microsoft/TypeScript
`!.` after `?.` should be warned
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Description
This is an anti-pattern on the current type system. And the compiler must not do quick fix so. !. after ?. is simply replaceable with ?. and should do so.
TypeScript Version: 3.7.x-dev.20191105
Search Terms:
Code
document.querySelector('_')!.textContent!.split('') // old code
document.querySelector('_')?.textContent!.split('') ?? 0 // string[]
document.querySelector('_')?.textContent?.split('') ?? 0 // string[] | 0
Expected behavior:
document.querySelector('_')!.textContent!.split('') // old code
document.querySelector('_')?.textContent!.split('') ?? 0 // unsafe, warning
document.querySelector('_')?.textContent?.split('') ?? 0 // safe
Actual behavior:
document.querySelector('_')!.textContent!.split('') // old code
document.querySelector('_')?.textContent!.split('') ?? 0 // unsafe, no warning
document.querySelector('_')?.textContent?.split('') ?? 0 // safe
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Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start by reproducing the examples in the TypeScript nightly playground and inspect the compiler diagnostics handling for optional chaining and non-null assertions. The change is done when !. following ?. produces a warning, no quick fix is offered, and the unsafe and safe examples are covered by a regression test.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- typescript
- Domain
- compilers
- Issue type
- Feature
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100