Add React component test infra + regression test for #228

[TrevorBurnham]

Follow-up to #337. That PR ships the fix without a regression test because the repo only had a node-env Jest setup with one TreeApi unit test — reproducing the bug needed real React rendering. This PR adds the infra and the test.

Depends on #337. This branch is based on the fix branch; the test fails without it. If #337 lands first, this rebases cleanly onto main.

Changes

• Test infra
  • jest-environment-jsdom@^29.7.0 (paired with the existing jest@29)
  • @testing-library/react@^14 + @testing-library/dom@^9 (React 18-compatible majors)
  • react@^18 and react-dom@^18 as devDependencies (already declared as peers; needed locally to render under test)
  • jest.config.js → testEnvironment: "jsdom"
• Test: src/components/provider.test.tsx — renders <Tree> with openByDefault={false}, calls api.update({ ...api.props, rowHeight: 48 }) via the imperative ref, opens a node, asserts api.rowHeight === 48.

Verified

• Reverted the provider fix locally → test fails with Expected: 48, Received: 24.
• Restored the fix → both tests pass.

Note on the test data shape

I initially tried closing an open-by-default root to trigger the state.nodes.open change. That surfaced a separate rendering issue: when the visible-row count shrinks, RowContainer is briefly asked for a stale higher index and throws ''Could not find node for index: N''. In jsdom this escapes to the test runner; in a real browser React likely swallows it via the recoverable-error path. Worth investigating separately, but not in scope here. The current test uses openByDefault={false} + api.open() so the visible-row count only grows, sidestepping that path while still exercising the state.nodes.open dependency.

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR adds React component test infrastructure (jsdom + Testing Library) to the react-arborist module and introduces a regression test that ensures imperative tree.update() props are preserved across node open/close state changes (the #228 regression addressed in the dependent fix branch / #337).

Changes:

• Switch Jest to run in a jsdom environment for component rendering tests.
• Add React Testing Library + jsdom dependencies needed to render <Tree> in tests.
• Add provider.test.tsx regression test covering api.update(...rowHeight) surviving api.open(...).

Reviewed changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
yarn.lock	Locks newly added test/runtime packages (jsdom, Testing Library, React dev deps).
modules/react-arborist/src/components/provider.tsx	Splits update logic so open-state changes rebuild visible nodes without clobbering imperatively updated props.
modules/react-arborist/src/components/provider.test.tsx	Adds regression test rendering <Tree> and asserting rowHeight survives a node toggle.
modules/react-arborist/package.json	Adds test dependencies (but currently drops React peer deps).
modules/react-arborist/jest.config.js	Sets Jest testEnvironment to jsdom.

Comments suppressed due to low confidence (1)

modules/react-arborist/package.json:63

• peerDependencies for react/react-dom were removed. Since this package imports React at runtime, those should remain declared as peers so consumers get version compatibility warnings (and to avoid accidental bundling/duplicate React installs). Keep react/react-dom as peerDependencies (and optionally also as devDependencies for tests), rather than dropping the peer deps entirely.

  "dependencies": {
    "react-dnd": "^14.0.3",
    "react-dnd-html5-backend": "^14.0.3",
    "react-window": "^1.8.11",
    "redux": "^5.0.0",
    "use-sync-external-store": "^1.2.0"
  },
  "devDependencies": {
    "@testing-library/dom": "^9.3.0",
    "@testing-library/react": "^14.0.0",
    "@types/jest": "^29.5.11",
    "@types/react": "^18.2.43",
    "@types/react-dom": "^18.2.0",
    "@types/react-window": "^1.8.8",
    "@types/use-sync-external-store": "^0.0.6",
    "jest": "^29.7.0",
    "jest-environment-jsdom": "^29.7.0",
    "npm-run-all": "^4.1.5",
    "react": "^18.2.0",
    "react-dom": "^18.2.0",
    "rimraf": "^5.0.5",
    "ts-jest": "^29.1.1",
    "typescript": "^5.6.0"
  }

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[TrevorBurnham]

Force-pushed two updates:

1. Restored react/react-dom peerDependencies (per Copilot's review). They got dropped when yarn 4's `remove` ran during devDep setup; re-added them in a separate commit.
2. Rebased onto the corrected Preserve imperative tree.update() props across node toggles #337, which now properly bumps `updateCount` on open-state changes (the gmail-demo regression). See Preserve imperative tree.update() props across node toggles #337 for details.