Keen Yee Liau 81241af7ac fix(language-service): Suggest ? and ! operator on nullable receiver (#35200)
Under strict mode, the language service fails to typecheck nullable
symbols that have already been verified to be non-null.

This generates incorrect (false positive) and confusing diagnostics
for users.

To work around this issue in the short term, this commit changes the
diagnostic message from an error to a suggestion, and prompts users to
use the safe navigation operator (?) or non-null assertion operator (!).

For example, instead of

```typescript
{{ optional && optional.toString() }}
```

the following is cleaner:

```typescript
{{ optional?.toString() }}
{{ optional!.toString() }}
```

Note that with this change, users who legitimately make a typo in their
code will no longer see an error. I think this is acceptable, since
false positive is worse than false negative. However, if users follow
the suggestion, add ? or ! to their code, then the error will be surfaced.
This seems a reasonable trade-off.

References:

1. Safe navigation operator (?)
   https://angular.io/guide/template-syntax#the-safe-navigation-operator----and-null-property-paths
2. Non-null assertion operator (!)
   https://angular.io/guide/template-syntax#the-non-null-assertion-operator---

PR closes https://github.com/angular/angular/pull/35070
PR closes https://github.com/angular/vscode-ng-language-service/issues/589

PR Close #35200
2020-02-10 16:43:44 -08:00
..
2020-01-13 07:21:43 -08:00

Angular

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Usage information and reference details can be found in Angular documentation.

License: MIT