fix(ivy): reuse compilation scope for incremental template changes. - #31932

Use .has for map key presence and not || null

Honestly, I think that this results in more verbose, ugly and less clear code:

  getScopeForComponent(clazz: ClassDeclaration): LocalModuleScope|null {
    const metadata = this.metadata.has(clazz.getSourceFile()) ?
        this.metadata.get(clazz.getSourceFile()) ! :
        null;
    return metadata && metadata.componentScope.has(clazz) ? metadata.componentScope.get(clazz) ! :
                                                            null;
  }

Notice the repetition and the need to use the ! operator.

I think it is fair to use has() when the type of the stored object could be falsy. But where a falsy return from get() can only mean the value was not there, then I think it is better to avoid the extra call to has().

Slightly cleaner version, which I can accept:

  getScopeForComponent(clazz: ClassDeclaration): LocalModuleScope|null {
    if (!this.metadata.has(clazz.getSourceFile())) {
      return null;
    }
    const metadata = this.metadata.get(clazz.getSourceFile()) !;
    if (!metadata.componentScope.has(clazz)) {
      return null;
    }
    return metadata.componentScope.get(clazz) !;
  }

I live for the day .has() will narrow the type of a subsequent .get() 😁

OOC wouldn't doing just a get be more performant anyway if you need the value? I see has for the use case of just testing whether or not a key exists without needing the actual value.

Can you file a JIRA and add a TODO here...

Remote scoping is gonna be tricky. If a component requires remote scoping, it means that the component's template changing requires the module to be re-emitted. Also, we need to make sure the cycle detector works well across rebuilds. Incremental compilation is ugly.

Done https://angular-team.atlassian.net/browse/FW-1501