fix(ToggleSwitch): fire onChange from the interaction instead of an effect

[mattcosta7]

Overview

For a controlled ToggleSwitch, onChange was fired from an effect rather than from the user interaction:

useEffect(() => {
  if (onChange && isControlled && !disabled) onChange(Boolean(checked))
}, [onChange, checked, isControlled, disabled])

Because the effect is keyed on onChange and checked, this caused onChange to fire:

• on mount (no user interaction),
• whenever the parent changes checked (echoing a change the parent already made), and
• on every render when onChange is an inline function (a new identity each render re-runs the effect).

This PR moves onChange to the interaction handler, where a controlled input should call it, and deletes the effect:

const handleToggleClick = e => {
  if (disabled || loading) return
  const next = !isOn
  if (isControlled) onChange?.(next)   // notify on the actual interaction
  else setIsOn(next)                    // uncontrolled: setIsOn already notifies onChange
  onClick?.(e)
}

Changelog

Fixed

• ToggleSwitch: onChange no longer fires on mount, on external checked changes, or on every render with an inline handler. It now fires on user interaction, as expected for a controlled input.

Rollout strategy

• Patch release
• Minor release
• Major release
• None

Testing & Reviewing

• The existing controlled-onChange test still passes (the click still reports the new value).
• Added a regression test asserting onChange does not fire on mount or on an external checked change.
• Full ToggleSwitch suite (17 tests) passes.

Note: this is a behavior change — consumers that (perhaps unintentionally) relied on onChange firing on mount/checked changes will no longer see those calls.

Merge checklist

• Added/updated tests
• Added/updated documentation
• Added/updated previews (Storybook)
• Changes are SSR compatible
• Tested in Chrome
• Tested in Firefox
• Tested in Safari
• Tested in Edge

[github-actions]

⚠️ Action required

👋 Hi, this pull request contains changes to the source code that github/github-ui depends on. If you are GitHub staff, test these changes with github/github-ui using the integration workflow. If this doesn't work, you can also use the original workflow here. Check the integration testing docs for step-by-step instructions. Or, apply the integration-tests: skipped manually label to skip these checks.

To publish a canary release for integration testing, apply the Canary Release label to this PR.

[changeset-bot]

🦋 Changeset detected

Latest commit: cc87dff

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@primer/react	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[primer-integration]

Integration test results from github/github-ui PR:

  CI Passed
  VRT Running
  Projects Waiting

[Copilot]

Pull request overview

This PR fixes ToggleSwitch controlled-mode behavior so onChange is fired from the actual user interaction instead of a useEffect, preventing unintended calls on mount, on externally-driven checked updates, and on rerenders where onChange changes identity.

Changes:

• Move controlled onChange invocation into the click handler and remove the effect that previously echoed checked changes.
• Add a regression test ensuring onChange is not called on mount or when checked changes externally.
• Add a patch changeset documenting the behavior fix.

Show a summary per file

File	Description
packages/react/src/ToggleSwitch/ToggleSwitch.tsx	Removes effect-driven onChange and triggers onChange from the interaction handler for controlled usage.
packages/react/src/ToggleSwitch/ToggleSwitch.test.tsx	Adds regression coverage for unintended onChange calls in controlled mode.
.changeset/toggleswitch-onchange-from-handler.md	Documents the patch-level behavioral fix for consumers.

Copilot's findings

• Files reviewed: 3/3 changed files
• Comments generated: 2