docs: fix code example in HeroService

[romamatusevich]

getHeroes method is syncronous and returns this.heroes immediately. At the same time getAll method in BackendService returns resolved Promise that is why thenable chain should be returned and used.

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/angular/angular/blob/main/CONTRIBUTING.md#commit
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Documentation content changes
• angular.io application / infrastructure changes
• Other... Please describe:

What is the current behavior?

getHeroes returns this.heroes immediately.

Issue Number: N/A

What is the new behavior?

getHeroes returns thenable Promise chain.

Does this PR introduce a breaking change?

• Yes
• No

Other information

[pkozlowski-opensource]

This is good catch. I'm not sure if we need the explicit return type (PromiseLike<Hero[]>) as TypeScript will infer it for us. Personally I try to avoid adding info that TypeScript can figure out by itself, but I can see how it could be helpful for documentation / understanding.

WDYT?

[pkozlowski-opensource]

Looking at the whole example again and suggested modification - the example is kind of broken now since it mentions cache but it doesn't use any caching in the way it is "written". So we would need to modify the code example to remove caching bits.

[romamatusevich]

Yes, maybe explicit type is not so useful here that is why I removed it. Also removed the comment regarding cache.

[pkozlowski-opensource]

I'm assuming that we are talking about example on this page: https://angular.io/guide/architecture-components#introduction-to-components-and-templates , right?

If so I think that the example is fine as-is. It is just a simple code snippet that doesn't assume anything about the HeroService implementation, and specifically nothing about it being async.

Please revert.

[romamatusevich]

Reverted

[pkozlowski-opensource]

Thnx for this PR. I've left some comments I would like to see addressed.

[romamatusevich]

Thnx for this PR. I've left some comments I would like to see addressed.

@pkozlowski-opensource, thank you for the comments. I've applied the changes. At the same time revert of changes in hero-list.component.ts leads to broken tests 'test_docs_examples' (hero-list.component.ts depends on getHeroes method in hero.service.ts). So, there are several options:

• apply changes for hero-list.component.ts
• leave everything as it was before and just close PR
• make hero-list.component.ts and hero-list.component.ts independent from tests perspective aka remove tests (I personally against it)

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