fix: show protocol handshake failures on the page (#213) - #260
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The handshake throws during the first hook mount, so a mismatch left a blank page whose only explanation was a DevTools console message. Every fatal handshake path now routes through `throwVisibly()`, which paints a fixed `#shinyreact-fatal-error` banner (role="alert") carrying the same text before throwing: the major mismatch in either direction, and the npm build's missing-tag / missing-protocolVersion errors. Plain DOM, no dependency on Shiny being initialized — the reported failure is that client and server cannot talk to each other. Literals (both versions, `#shinyreact-config`, `@posit/shinyreact`) are marked with backticks and render as `<code>` chips; the backticks are stripped from the thrown error and the console-only warning. Text is set with textContent, so a server-supplied version cannot inject markup. Colors are #7f1d1d on #fee2e2 (~9.5:1). Tests: unit coverage in config.test.ts for both mismatch directions, chip markup, HTML-injection safety, banner reuse, and throw/display parity; a Playwright e2e (apps/protocol_mismatch) asserting the banner is on screen and the app body never rendered.
# Conflicts: # pkg-js/dist/shinyreact.js # pkg-py/src/shinyreact/www/shinyreact.js # pkg-r/inst/lib/shiny/shinyreact.js
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Closes #213.
The protocol handshake throws during the first hook mount, so a mismatch left the page blank with the explanation only in the DevTools console.
What changed
Every fatal handshake path now goes through
throwVisibly()inpkg-js/src/shiny-react/config.ts, which paints a fixed banner and then throws the same message:assertProtocolCompatible)#shinyreact-configtagprotocolVersionFail fast is unchanged — the banner is additive.
Details:
<div id="shinyreact-fatal-error" role="alert">appended to<body>, one element reused across repeated failures.#shinyreact-config,@posit/shinyreact) are backticked in the message and render as<code>chips. Backticks are stripped from the thrown error and from the console-only warning.textContent, neverinnerHTML, so a server-supplied version string cannot inject markup.role="alert"carry the meaning.What it looks like
(versions rendered as
<code>chips, dark maroon on a pale red banner across the top)Tests
pkg-js/src/shiny-react/__tests__/config.test.ts: both mismatch directions, chip markup, HTML-injection safety, single-element reuse, throw/display parity, backtick stripping.npx vitest run→ 263 pass.pkg-py/tests/playwright/test_protocol_mismatch.py+ fixtureapps/protocol_mismatch/(server monkeypatched to claim protocol999.0): banner visible with both versions, chips,role="alert", and the app body never rendered.make py-test-e2e→ 11 pass.make py-check-tests→ 146 pass.make js-lintclean.make update-distrun.FEATURES.mdupdated with the new[js]subtree.Not done
No
Shiny.notifications.show()/ dev-mode error console surface. Shiny's error console is fed by server errors, not client throws, and notifications need Shiny initialized — exactly what is unreliable at the moment the handshake fails. Worth revisiting once the npm tier lands.