Quest: Sync with starbeam developments: (and actually get the lint implemented, since we have some footguns to protect against)

[NullVoxPopuli]

Tasks

• on.sync

  • manages changes in consumed reactive values
  • allows cleanup behavior to occur per set of reactive changes

• on.cleanup becomes on.finalize (but keep on.cleanup for compatibility)

• Lints

  • finish #709
  • add
    • family of lints for inlining resource definitions within the class body
      • explore forbidding consumption of tracked args within the resource body (can lint against arg usage specifically
        • potentially auto-fixable to on.sync + return cleanup function
      • favor linting for the returned () => return value, because returning lazily accessed () => this.args.input is fine, but returning this.args.input is not.
      • prefer defining resources in module space

• Learning materials

  • the resource body is "the constructor"-
  • on.sync allows easy managing of reactive updates, no worry about the whole thing getting torn down prematurely
  • on.finalize (formally on.cleanup) is tied to the lifetime of the parent context
  • before and after docs
    • how to be closest to starbeam
    • what was awkward before that resources make better

Notes:

resource(({ on }) => {
  evaluateCount++;
  on.sync(() => () => cleanupCount++);

  // THIS IS ILLEGAL. You can't read reactive values in the constructor
  // (because the entire would be torn down each time @input @changes)
  return this.args.input;
});

should instead be

resource(({ on }) => {
  on.sync(() => {
    syncCount++;
    return () => cleanupCount++;
  });

  return Formula(() => this.args.input);
});

however, Formula doesn't exist in ember-resources, and may not make sense today, as ember-resources already supports returning () => some value, and it's already a "cached value" (via the createCache api (which is internal in the helper managers)

[NullVoxPopuli]

Note: on.sync us impossfto implement in ember, pre-starbeam.

But moving the resource body into on.sync in the codemod should be safe/consistent