Dropdown: Accessibility contract
Specifies semantics, keyboard behavior, focus handling, announcements, and inclusive interaction rules for dropdown. This reference fixes the adoption boundary, failure behavior, and observable evidence while leaving environment-specific limits configurable.
Package status: reference context ready for human review. The contract and test scenarios are complete, but no claim is made that an adopting implementation has passed them.
Decision
For Dropdown, adopt a reusable state and interaction contract using native semantics where available. Specify semantic, keyboard, focus, announcement, visual, motion, and error behavior as part of the component's functional contract. This package is a reference contract: the adopting team must choose numeric limits, providers, jurisdictions, and operational owners from evidence in its own environment.
Scope
- The Dropdown actors, inputs, outputs, states, policy or schema versions, and externally visible outcomes described by this accessibility block.
- Primary and alternate interfaces, background work, caches, integrations, support paths, and evidence that can exercise the same boundary.
- Adoption-specific configuration, rollout, recovery, and verification responsibilities needed to apply the reference safely.
Outside this block
- Choosing a universal vendor, framework, jurisdiction, numeric threshold, retention period, or service-level objective for every adopter.
- Claiming that packaged scenarios have run against a downstream implementation or that this reference grants legal, security, or accessibility certification.
Contract
- Define trigger, open or active, loading, success, empty, invalid, error, disabled, and dismissal states that the pattern can enter.
- Specify keyboard input, focus entry and return, accessible name, announcements, pointer behavior, and touch target behavior together.
- Make destructive, irreversible, or external effects explicit and prevent duplicate activation while work is pending.
- Keep content hierarchy and actions usable at narrow widths, high zoom, text expansion, forced colors, and reduced motion.
- Prefer native elements; when a custom widget is necessary, implement its complete expected interaction pattern rather than only adding a role.
- Test with multiple input modes and at least one representative screen-reader/browser combination defined by the adopting team.
- Expose a persistent label, current value, expanded state, option identity, selection mode, disabled state, and keyboard behavior using native select semantics or a documented composite pattern.
- Keep focus and active option stable through filtering, virtualization, async loading, invalidation, and responsive presentation and provide a clear empty, error, and recovery state.
Implementation guidance
- Write the keyboard and focus sequence before implementation and review copy with visible labels and programmatic names side by side.
- Model Dropdown inputs, outputs, actors, states, invariants, side effects, and evidence before selecting framework or vendor details.
- Store the applicable Dropdown contract or policy version with material state so migrations, replay, and support decisions remain attributable.
- Introduce the path behind controlled rollout, compare expected and observed outcomes, and keep a tested recovery route until adoption evidence is complete.
Failure handling and safeguards
- On failed action, preserve relevant input and focus, announce the result, and return the component to a state with a safe recovery path.
- Invalid or contradictory Dropdown state is rejected or quarantined; the implementation never guesses a value that broadens authority or duplicates an effect.
- Retries are bounded and use durable identity; after exhaustion, work reaches an inspectable terminal state with an accountable owner.
Verification and operations
- Verify automated rules, keyboard-only operation, focus visibility, announcements, contrast, zoom, and manual task completion.
- Monitor Dropdown success, denial, validation failure, dependency failure, retry exhaustion, and recovery by contract version without sensitive payload dimensions.
- Re-run paired positive and negative fixtures after policy, schema, dependency, migration, or boundary changes and preserve the resulting evidence.
Adoption assumptions
- Names and values in the example are a concrete fixture, not universal defaults; adopters replace them through documented evidence and ownership.
- The adopting system can provide authenticated identity, durable operation or record versions, bounded telemetry, and a controlled path for change.
The executable-looking examples in this package are fixtures and acceptance contracts. Run the collection validator to check structure and metadata, then translate and execute the scenarios in the target repository before recording implementation evidence.