[boboshan]

Description

ElementSnapshot reads role, label, value and the state flags from an observed element's native node, but not its description or placeholder, so a UI test cannot check either on a painted element. Both reach assistive technology: Base's input editor writes aria_placeholder (gpui-component's Input passes its placeholder there), and the questionnaire and diff controls write aria_description. Today a test can only check them by building the element and calling write_a11y_info by hand, as focus_trap.rs and lifecycle.rs do, which reaches the outermost element and not one painted inside a view. GPUI's Window::debug_a11y_tree_json() includes both, but a test window never activates accessibility, so it returns None.

This follows #3531, which added disabled() the same way. Snapshots now record description and placeholder from the node they already read label from. A frame with a semantic owner takes both from its editor, like its other semantic facts, so an Input's placeholder is found through the component ID.

We need this in an application's tests: a picker trigger with nothing chosen gives its prompt as a placeholder and no value, so a screen reader does not read the prompt as the choice, and a toggle without a visible label announces its description.

Public API

gpui-base

• test_support::ElementSnapshot::description(&self) -> Option<&str> — the accessibility description, read after the label; it does not replace it.
• test_support::ElementSnapshot::placeholder(&self) -> Option<&str> — the accessibility placeholder, the prompt shown while the element has no value.

Both are also reachable through gpui_kit::test::ElementSnapshot. ElementSnapshot's Debug output lists the two fields after label.

How to Test

• snapshot_reads_description_and_placeholder (crates/kit/tests/integration/lifecycle.rs) paints an observed div with a label, description and placeholder, and reads all three with no value.
• placeholder_is_read_from_the_editor_and_is_not_a_value (crates/kit/tests/integration/input.rs) paints a component Input with a label and a placeholder, and reads the placeholder through the semantic owner with an empty value.
• Negative controls: without the capture in prepaint, both tests fail; without the two fields in the semantic-owner snapshot, only the Input test fails.
• The English and Chinese testing and accessibility guides list the two readers.
• On this branch, macOS, Rust 1.99.1: cargo test -p gpui-kit --features test-support,component --locked, cargo test -p gpui-base --features test-support --lib --locked, cargo clippy -p gpui-base -p gpui-kit --features gpui-kit/test-support,gpui-kit/component --all-targets --locked -- --deny warnings, cargo fmt --all --check and typos 1.40.0.

Checklist

• I have read the CONTRIBUTING document and followed the guidelines.
• Reviewed the changes in this PR and confirmed AI generated code (If any) is accurate.
• Passed cargo run for story tests related to the changes.
• Tested macOS, Windows and Linux platforms performance (if the change is platform-specific)

🤖 Generated with Claude Code