fix(lit-virtual): add setOptions to VirtualizerController for reactive option updates

[waterWang]

Description

Fixes #1251

() never calls after the initial construction, so reactive option updates (a changed , , , etc.) never reach the underlying instance.

Root cause

The constructor captures options once and passes them to . The lifecycle method only calls without re-applying options. Every other framework adapter (, ) calls before every .

Fix

1. Added method to — stores the options on the instance, merges with new partial options, and calls + . Matches the pattern used by 's and 's injectable.

2. Stored as a private field — enables the method to merge partial updates with the base options (including defaults from and subclass constructors).

Consumer usage

Changes

• : Added method, stored as private field
• : Added test verifying renders items beyond the initial count of 10

Summary by CodeRabbit

• New Features

  • Added the ability to update virtualizer options dynamically during rendering.
  • Changes to options now immediately refresh the displayed item range and count.

• Tests

  • Added coverage confirming that updated item counts render newly available items correctly.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 25ca0c64-2677-4427-879d-32d97020388b

📥 Commits

Reviewing files that changed from the base of the PR and between d2cf98b and e548ded.

📒 Files selected for processing (2)

• packages/lit-virtual/src/index.ts
• packages/lit-virtual/tests/index.test.ts

---

📝 Walkthrough

Walkthrough

VirtualizerControllerBase now supports runtime option updates through setOptions(). The update path preserves callbacks, applies merged options to the virtualizer, and triggers its lifecycle. A test verifies that changing count renders item index 15.

Changes

Lit virtualizer option updates

Layer / File(s)	Summary
Controller option update flow packages/lit-virtual/src/index.ts	The controller stores its options and adds setOptions() to merge updates, rebuild onChange, update the virtualizer, and invoke _willUpdate().
Rendering validation packages/lit-virtual/tests/index.test.ts	A test changes the count from 10 to 20 during rendering and verifies that item index 15 renders.

Estimated code review effort: 2 (Simple) | ~10 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies the addition of setOptions for reactive lit-virtual option updates.
Description check	✅ Passed	The description explains the bug, root cause, implementation, issue reference, and test coverage, so it is mostly complete.
Linked Issues check	✅ Passed	The PR adds a public setOptions channel, merges options, updates the virtualizer, and tests reactive count changes as required by issue #1251.
Out of Scope Changes check	✅ Passed	The changes are limited to the requested controller API update and its focused regression test.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

Warning

There were issues while running some tools. Please review the errors and either fix the tool's configuration or disable the tool if it's a critical failure.

🔧 ESLint

If the error stems from missing dependencies, add them to the package.json file. For unrecoverable errors (e.g., due to private dependencies), disable the tool in the CodeRabbit configuration.

packages/lit-virtual/tests/index.test.ts

Parsing error: "parserOptions.project" has been provided for @typescript-eslint/parser.
The file was not found in any of the provided project(s): packages/lit-virtual/tests/index.test.ts

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}