fix: return JS eval results on Windows/WebView2 (execute_js/dom_snapshot/screenshot time out)#29
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The non-macOS execute_js path returns results through a JS->IPC postback
(invoke('plugin:mcp-bridge|script_result')) that never completes on WebView2,
so execute_js / dom_snapshot / the html2canvas screenshot fallback all time
out at the server's handshake. This is the same failure class that hypothesi#12 fixed
for macOS by switching to native evaluateJavaScript:completionHandler:.
Route synchronous scripts on non-macOS through Tauri's
WebviewWindow::eval_with_callback, which returns the result via WebView2's
ExecuteScript completion handler (WebKitGTK on Linux) with no JS postback —
the cross-platform analogue of the macOS native path. Async/Promise scripts
keep the existing IPC-callback fallback, since the callback only captures the
script's synchronous return value.
Verified on Windows 11 (WebView2, Tauri 2.11.2): execute_js, dom_snapshot,
and screenshot all return correctly where they previously timed out.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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Problem
On Windows (WebView2), every webview tool that returns a value —
webview_execute_js,webview_dom_snapshot, and the html2canvas / Screen-Capturewebview_screenshotfallbacks — fails withWebView execution failed: Request timeout after 2000ms. The WebSocket transport and all Rust-native commands (ipc_get_backend_state,manage_window, …) work fine; only the JS-eval result round-trip hangs.Root cause
execute_jsforks by OS. macOS uses nativeWKWebView evaluateJavaScript:completionHandler:— added precisely because "the eval-and-IPC-callback approach … fails on some setups." Every other platform falls through toeval_with_ipc_callback, which runs a fire-and-forgetwindow.eval()whose wrapper posts the result back viawindow.__TAURI__.core.invoke('plugin:mcp-bridge|script_result', …). On WebView2 that postback never completes, and the wrapper's.catchswallows the failure without falling through to theevent.emitbackup — so the Rustoneshotnever resolves and the server's 2000 ms handshake (waitForResolveRefHelper) times out.In other words, #12 was not macOS-specific — the same IPC-callback path also fails on Windows/WebView2; it was only worked around for macOS.
Fix
Route synchronous scripts on non-macOS through Tauri's
WebviewWindow::eval_with_callback, which hands the JSON-serialized result back through WebView2'sICoreWebView2::ExecuteScriptcompletion handler (WebKitGTK on Linux) — a real result channel with no JS→IPC postback, the cross-platform analogue of the macOS native path. Async/Promise scripts keep the existingeval_with_ipc_callbackfallback, since the callback only captures the script's synchronous return value.#[cfg(not(target_os = "macos"))]).{ success, data }/{ success, error }shape as the macOS path.Verification
Built and run on Windows 11 (WebView2, Tauri 2.11.2) against a real Tauri app, via a local path-override of the crate:
execute_js→ returns values (e.g.ok:complete:…:tauri=true)dom_snapshot→ full element tree with refsscreenshot→ native capture succeedsread_logs console→ worksAll four previously timed out at 2000 ms.
Related to #12 (extends that macOS fix to Windows/Linux).
🤖 Generated with Claude Code