This commit performs a modularization of the Language Service's existing
diagnostic messages. Such a modularization has two primary advantages:
- Centralization and decoupling of error messages from the code that
generates them makes it easy to add/delete/edit diagnostic messages,
and allows for independent iteration of diagnostic messages and
diagnostic generation.
- Prepares for additional features like annotating the locations where a
diagnostic is generated and enabling the configuration of which
diagnostics should be reported by the language service.
Although it would be preferable to place the diagnostics registry in an
independent JSON file, for ease of typing diagnostic types as an enum
variant of 'ts.DiagnosticCategory', the registry is stored as an object.
Part of #32663.
PR Close#35678
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
The following files are consumed only by the language service and do not
have to be in compiler-cli:
1. expression_diagnostics.ts
2. expression_type.ts
3. typescript_symbols.ts
4. symbols.ts
PR Close#33809
ayazhafiz
Keen Yee Liau