Reactivity by NullVoxPopuli · Pull Request #2219 · ember-learn/guides-source

NullVoxPopuli · 2026-06-11T22:33:10Z

Advancement PR:

Advance RFC #1071 "Overload tracked to work outside of classes" to Stage Ready for Release emberjs/rfcs#1202

Merged RFC PR:

Overload tracked to work outside of classes emberjs/rfcs#1071

Docs Inspirations:

Read Order:

netlify · 2026-06-11T22:33:14Z

✅ Deploy Preview for ember-guides ready!

Name	Link
🔨 Latest commit	`ffd867a`
🔍 Latest deploy log	https://app.netlify.com/projects/ember-guides/deploys/6a78dcf4830534000856b7a8
😎 Deploy Preview	https://deploy-preview-2219--ember-guides.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.
🤖 Make changes	Run an agent on this branch

To edit notification comments on pull requests, go to your Netlify project configuration.

- Motivation references the in-flight reactivity guides (ember-learn/guides-source#2219) instead of claiming docs are sparse - remove the derived-vs-cached clarification paragraph (the guides cover it; not an ambiguation) - move the RFC 615 relationship to the Appendix, without any de-emphasize/deprecate intent Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

johanrd · 2026-07-31T08:01:04Z

+previously in the same computation.
+```
+
+This is sometimes called the _backtracking assertion_: render evaluates your


-This is sometimes called the _backtracking assertion_: render evaluates your … +This backtracking assertion evaluates your …

johanrd · 2026-07-31T09:20:26Z

+When a write that changes nothing shouldn't dirty anything, the decorator
+accepts an options form, `@tracked({ equals })`, that skips invalidation


Very cool!

Depends on release of emberjs/ember.js#21471, right? starting with 7.3.0?

yea, tho I think these docs are required to release in 7.3

@kategengler knows the task<->dependency chain.

johanrd · 2026-07-31T10:15:11Z

@NullVoxPopuli this was a great read – thanks! Also very exited to learn about the overloaded tracked of 7.3.

- Motivation references the in-flight reactivity guides (ember-learn/guides-source#2219) instead of claiming docs are sparse - remove the derived-vs-cached clarification paragraph (the guides cover it; not an ambiguation) - move the RFC 615 relationship to the Appendix, without any de-emphasize/deprecate intent Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

@NullVoxPopuli

* Add RFC: Overload cached for non-class use Derived-state companion to RFC 1071 (overloaded tracked). Re-uses the Reactive/ReadOnlyReactive interfaces defined there; cached(fn, options) returns a read-only CachedValue. * Fill in proposal PR URL Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> * Do not conflate derived state with cached state Derived state is just plain functions and needs no API; cached() is opt-in memoization of a derivation. Reword Summary, Motivation, usage headings, and How We Teach accordingly. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> * Address review: guides link, drop terms paragraph, RFC 615 to appendix - Motivation references the in-flight reactivity guides (ember-learn/guides-source#2219) instead of claiming docs are sparse - remove the derived-vs-cached clarification paragraph (the guides cover it; not an ambiguation) - move the RFC 615 relationship to the Appendix, without any de-emphasize/deprecate intent Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> * Address review: drop equals, drop 'memoization' wording - remove the equals option from the proposed API entirely (calling fn is the expensive part; re-running it to discard the result is silly); noted as deferred in the Appendix - say caching, not memoization, throughout - reword the 'born a ReadOnlyReactive' sentence - drop the implementation-would-be-lower aside Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> * Apply suggestion from @NullVoxPopuli * Address review: get on ReadOnlyReactive, trim examples and mentions - no new CachedValue interface; add get to ReadOnlyReactive instead (an RFC 1071 oversight) and return ReadOnlyReactive from cached() - apply suggested guides sentence (drop 'over the years') - Starbeam only in prior art; resources are a different concept - remove the contrived nested-let template example Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> --------- Co-authored-by: NullVoxPopuli-ai-agent <268630448+NullVoxPopuli-ai-agent@users.noreply.github.com> Co-authored-by: NullVoxPopuli <199018+NullVoxPopuli@users.noreply.github.com>

Copilot

Pull request overview

Adds advanced reactivity guidance supporting RFC #1071’s release advancement.

Changes:

Adds guides for root state, derived state, and effects.
Expands autotracking documentation and cross-references.
Updates navigation and spelling terminology.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
`.local.dic`	Adds reactivity terminology.
`guides/release/pages.yml`	Adds reactivity navigation.
`guides/release/in-depth-topics/autotracking-in-depth.md`	Expands tracking references and examples.
`guides/release/in-depth-topics/reactivity/index.md`	Introduces the reactivity model.
`guides/release/in-depth-topics/reactivity/root-state.md`	Documents reactive root state.
`guides/release/in-depth-topics/reactivity/derived-state.md`	Documents derivations and caching.
`guides/release/in-depth-topics/reactivity/inputs-and-outputs.md`	Documents effects, lifetimes, and async behavior.

Suppressed comments (1)

guides/release/in-depth-topics/reactivity/root-state.md:230

Keeping a tracked array's identity stable is useful, but mutating it does not guarantee that only the changed entry's consumers invalidate: current trackedArray writes dirty the collection tag. Preserve the identity recommendation without promising narrower invalidation.

a one-item change gets treated as if the entire array were new. Retain
identity wherever possible: keep one long-lived tracked collection and mutate
it, so that the system invalidates only what actually changed. Replacement is

💡 Add a code-review agent skill or configure MCP servers for context-aware, tailored reviews. Learn more in the docs.

+Storing derived values is sometimes pitched as an optimization. However,
+autotracking already recomputes lazily, and only when inputs change, so the
+optimization is usually imaginary. When a derivation really is expensive, you
+can [cache it](../derived-state/#toc_caching) instead of promoting it to root
+state.


NullVoxPopuli · 2026-08-09T20:01:48Z

+`tracked` also works as a plain function. Called with a value instead of
+applied as a decorator, it returns a standalone reactive value - root state
+that isn't attached to any class:


while true, I'm not sure how beneficial it is to mention in these docs.

This is implementation caveats that are very edge casey.

NullVoxPopuli · 2026-08-09T20:03:59Z

+- Once-per-change semantics. If a derivation must observably run at most once
+  per change (because it allocates, logs, or is just very hot), `@cached`
+  guarantees that.


🤷 I don't know how to best phrase this. sounds good

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

Copilot

Pull request overview

Copilot reviewed 7 out of 7 changed files in this pull request and generated no new comments.

Suppressed comments (6)

guides/release/in-depth-topics/reactivity/root-state.md:209

This copy guarantee does not hold for trackedWeakMap or trackedWeakSet: weak collections are not iterable, so Ember wraps and mutates a supplied weak collection instead of cloning it. Narrow the guarantee or document that exception.

to know: the collection functions copy the data you pass in, so mutating the
tracked collection never mutates the original; and tracked collections are
shallow - `trackedObject`'s properties are tracked, but objects stored inside
it are ordinary objects unless you wrap them too. See

guides/release/in-depth-topics/reactivity/inputs-and-outputs.md:212

A promise can reject with a falsy reason such as undefined or null. In that case status becomes rejected, but this condition falls through to the success branch and dereferences this.user.value.name while value is still null. Select the branch from status, which is the request-state discriminator.

    {{else if this.user.error}}

guides/release/in-depth-topics/reactivity/index.md:114

This overstates the scope and lifetime of the conditional dependency: another consumer can still be invalidated by nickname, and displayName stops depending on it if the condition later switches back. Describe invalidation through this getter and only while its branch is active.

While `useNickname` is `false`, changes to `nickname` don't invalidate
anything, because `displayName` never read it. If `useNickname` becomes
`true`, the next evaluation reads `nickname`, and from then on changes to it
propagate. The dependency graph rewires itself on every run.

guides/release/in-depth-topics/reactivity/index.md:136

With the new @tracked({ equals }) form, a write invokes the user-provided equality callback synchronously, so it is no longer true that no user code runs. The pull-based guarantee is specifically that writes do not execute derivations/getters; phrase it in those terms.

Autotracking is pull-based. When you write to a tracked property, no user
code runs at all. Your getters are not re-evaluated; nothing is recomputed.
The write just lets the renderer know that something it consumed is out of

guides/release/in-depth-topics/reactivity/derived-state.md:199

tracked is unused in this example. Keeping the import makes copied code fail the default unused-import lint rule and obscures that a plain function needs no tracking API.

import { tracked } from '@glimmer/tracking';

guides/release/in-depth-topics/reactivity/inputs-and-outputs.md:88

This chart is canvas-only, so its data has no accessible text representation for screen-reader users. Add an equivalent table/summary or an accessible name and description derived from the chart data; the appropriate representation depends on the data being visualized.

  <canvas {{drawChart @chartData}}></canvas>

NullVoxPopuli added 2 commits July 23, 2026 11:17

Reactivity

a8fef4c

wip

f93c0cf

NullVoxPopuli force-pushed the nvp/reactivity branch from 9553b2f to f93c0cf Compare July 23, 2026 18:10

NullVoxPopuli added 4 commits July 23, 2026 14:38

Up

8a84477

Up

2003404

Up

142e41b

Up

3befb9d

NullVoxPopuli mentioned this pull request Jul 31, 2026

Overload cached for non-class use NullVoxPopuli/rfcs#19

Merged

johanrd reviewed Jul 31, 2026

View reviewed changes

Comment thread guides/release/in-depth-topics/reactivity/derived-state.md Outdated

johanrd reviewed Jul 31, 2026

View reviewed changes

Comment thread guides/release/in-depth-topics/reactivity/index.md Outdated

johanrd reviewed Jul 31, 2026

View reviewed changes

Comment thread guides/release/in-depth-topics/reactivity/root-state.md Outdated

johanrd reviewed Jul 31, 2026

View reviewed changes

Comment thread guides/release/in-depth-topics/reactivity/root-state.md

Feedback

67ae08b

NullVoxPopuli mentioned this pull request Aug 9, 2026

Advance RFC #1071 "Overload tracked to work outside of classes" to Stage Ready for Release emberjs/rfcs#1202

Open

12 tasks

NullVoxPopuli requested a balanced review from Copilot August 9, 2026 19:36

Copilot started reviewing on behalf of NullVoxPopuli August 9, 2026 19:36 View session

Copilot AI reviewed Aug 9, 2026

View reviewed changes

Potential fix for pull request finding

ffd867a

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

NullVoxPopuli requested a balanced review from Copilot August 9, 2026 20:05

Copilot started reviewing on behalf of NullVoxPopuli August 9, 2026 20:05 View session

Copilot AI reviewed Aug 9, 2026

View reviewed changes

Navigation Menu

Uh oh!

Uh oh!

Reactivity - #2219

Reactivity#2219
NullVoxPopuli wants to merge 8 commits into
ember-learn:masterfrom
NullVoxPopuli:nvp/reactivity

NullVoxPopuli commented Jun 11, 2026 •

edited

Loading

Uh oh!

netlify Bot commented Jun 11, 2026 •

edited

Loading

Uh oh!

Uh oh!

johanrd Jul 31, 2026

Uh oh!

Uh oh!

johanrd Jul 31, 2026

Uh oh!

NullVoxPopuli Jul 31, 2026

Uh oh!

Uh oh!

Uh oh!

johanrd commented Jul 31, 2026

Uh oh!

Copilot AI left a comment

Uh oh!

Uh oh!

Uh oh!

NullVoxPopuli Aug 9, 2026

Uh oh!

NullVoxPopuli Aug 9, 2026

Uh oh!

Uh oh!

Copilot AI left a comment

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

3 participants

		When a write that changes nothing shouldn't dirty anything, the decorator
		accepts an options form, `@tracked({ equals })`, that skips invalidation

Uh oh!

Uh oh!

Conversation

NullVoxPopuli commented Jun 11, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

netlify Bot commented Jun 11, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

✅ Deploy Preview for ember-guides ready!

Uh oh!

Uh oh!

johanrd Jul 31, 2026

Choose a reason for hiding this comment

Uh oh!

Uh oh!

johanrd Jul 31, 2026

Choose a reason for hiding this comment

Uh oh!

NullVoxPopuli Jul 31, 2026

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

johanrd commented Jul 31, 2026

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull request overview

Reviewed changes

Uh oh!

Uh oh!

Uh oh!

NullVoxPopuli Aug 9, 2026

Choose a reason for hiding this comment

Uh oh!

NullVoxPopuli Aug 9, 2026

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull request overview

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

3 participants

NullVoxPopuli commented Jun 11, 2026 •

edited

Loading

netlify Bot commented Jun 11, 2026 •

edited

Loading