[combobox] Clear value on Escape from Trigger in input-inside-popup

[spokodev]

Fixes #4938.

In the input-inside-popup pattern (<Combobox.Trigger> outside, <Combobox.Input> inside <Combobox.Popup>), Combobox.Trigger was the keyboard entry point when the popup was closed, but it had no handler for Escape. So users could not clear a selected value without first opening the popup, focusing the Input, and pressing Escape there. The issue author posted a manual workaround that simulated a click on Combobox.Clear.

This adds an Escape branch to Combobox.Trigger's onKeyDown that mirrors the existing clear path in ComboboxInput.tsx (around line 399): it only fires when inputInsidePopup is true and the popup is not mounted, calls setSelectedValue with null (single) or [] (multiple), and stops propagation only when there was something to clear, not inline, and propagation was not explicitly allowed. disabled and readOnly are respected via the early return at the top of the handler.

Combobox.Input in the outside-popup pattern keeps its existing behavior. The Trigger handler only activates when the popup is closed, so when the popup is open the Escape goes through the Input as before.

11 new tests in ComboboxTrigger.test.tsx cover:

• Two positive cases (single value cleared to null, multi to [])
• Three negative cases (Tab on Trigger no-op; Trigger in input-outside-popup no-op; Trigger Escape while popup is open does not duplicate Input's clear)
• Six edge cases (no value selected, Trigger disabled, Combobox.Root disabled, Combobox.Root readOnly, controlled value flow, details.reason === REASONS.escapeKey)

All four fail on master and pass on this branch.

Verification

pnpm test:jsdom ComboboxTrigger --no-watch
# 54 passed | 1 skipped (55)

pnpm test:jsdom Combobox --no-watch
# 685 passed | 17 skipped (702) across 25 test files

pnpm typescript
# clean

pnpm eslint packages/react/src/combobox/trigger/ComboboxTrigger.tsx packages/react/src/combobox/trigger/ComboboxTrigger.test.tsx
# clean

pnpm prettier --check packages/react/src/combobox/trigger/
# clean

Open as draft until CI confirms.

[pkg-pr-new]

• base-ui-tanstack-start

• vite-css-base-ui-example

  pnpm add https://pkg.pr.new/mui/base-ui/@base-ui/react@4946
  

  pnpm add https://pkg.pr.new/mui/base-ui/@base-ui/utils@4946
  

commit: 4deae86

[code-infra-dashboard]

Bundle size

Bundle	Parsed size	Gzip size
@base-ui/react	🔺+246B(+0.05%)	🔺+39B(+0.03%)

Details of bundle changes

Performance

Total duration: 1,122.83 ms +24.80 ms^(+2.3%) | Renders: 50 ⁽⁺⁰⁾ | Paint: 1,687.75 ms +17.78 ms^(+1.1%)

Test	Duration	Renders
Popover mount (300 instances)	75.69 ms 🔺+15.04 ms(+24.8%)	1 (+0)
Mixed surface mount (app-like density)	57.86 ms ▼-16.55 ms(-22.2%)	5 (+0)

10 tests within noise — details

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