windows smoke: opt-in WebView2 DevTools port via LOTUS_WEBVIEW2_DEBUG_PORT (#19)

WebView2's WEBVIEW2_ADDITIONAL_BROWSER_ARGUMENTS is ignored because the app
sets its browser arguments explicitly (seen on the runner: the WebView2
command line had only the app's arguments). The app now appends
--remote-debugging-port only when LOTUS_WEBVIEW2_DEBUG_PORT holds a valid
port (>= 1024); otherwise the arguments are exactly as before.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA

.gitea/workflows/windows-smoke.yml

@@ -95,7 +95,9 @@ jobs:
           Copy-Item scripts\windows-smoke.mjs smoke-deps\windows-smoke.mjs
           # Same step as the test: a process started in an earlier step may be
           # cleaned up when that step ends.
-          $env:WEBVIEW2_ADDITIONAL_BROWSER_ARGUMENTS = '--remote-debugging-port=9222 --use-fake-device-for-media-stream'
+          # The app sets its own WebView2 arguments, so WebView2's env var doesn't
+          # apply; the app opens the DevTools port itself when asked (#19).
+          $env:LOTUS_WEBVIEW2_DEBUG_PORT = '9222'
           $app = Join-Path $env:LOCALAPPDATA 'Lotus Chat\cinny.exe'
           Start-Process $app
           Start-Sleep -Seconds 15

src-tauri/src/lib.rs

@@ -1128,9 +1128,9 @@ pub fn run() {
                 // Tauri's default WebView2 args (setting this overrides them) and
                 // appends the Chromium background-throttling disables. Windows-only
                 // in effect; harmless elsewhere. Does not block system sleep.
-                .additional_browser_args(
-                    "--disable-features=msWebOOUI,msPdfOOUI --disable-background-timer-throttling --disable-renderer-backgrounding --disable-backgrounding-occluded-windows",
-                )
+                .additional_browser_args(&webview2_browser_args(
+                    std::env::var("LOTUS_WEBVIEW2_DEBUG_PORT").ok().as_deref(),
+                ))
                 .on_page_load(move |window, payload| {
                     if matches!(payload.event(), PageLoadEvent::Finished) {
                         // Reveal only on the FIRST settle: later page loads (e.g. a
@@ -1289,6 +1289,44 @@ pub fn run() {
         .expect("error while building tauri application");
 }
 
+/// WebView2 browser arguments. Setting them replaces Tauri's defaults, so
+/// they're kept, plus the Chromium background-throttling disables (P5-42).
+///
+/// cinny-desktop #19: `LOTUS_WEBVIEW2_DEBUG_PORT=<port>` in the environment
+/// opens WebView2's DevTools port on localhost so the Windows smoke test can
+/// drive the installed app. WebView2's own `WEBVIEW2_ADDITIONAL_BROWSER_ARGUMENTS`
+/// doesn't apply because the app sets its arguments explicitly. Off unless the
+/// variable holds a valid port; only whoever launches the app can set it.
+pub(crate) fn webview2_browser_args(debug_port: Option<&str>) -> String {
+    let mut args = String::from(
+        "--disable-features=msWebOOUI,msPdfOOUI --disable-background-timer-throttling --disable-renderer-backgrounding --disable-backgrounding-occluded-windows",
+    );
+    if let Some(port) = debug_port
+        .and_then(|p| p.trim().parse::<u16>().ok())
+        .filter(|p| *p >= 1024)
+    {
+        eprintln!("webview: DevTools port {port} open (LOTUS_WEBVIEW2_DEBUG_PORT)");
+        args.push_str(&format!(" --remote-debugging-port={port}"));
+    }
+    args
+}
+
+#[cfg(test)]
+mod webview2_args_tests {
+    use super::webview2_browser_args;
+
+    #[test]
+    fn debug_port_only_when_asked_for_and_valid() {
+        let base = webview2_browser_args(None);
+        assert!(base.contains("--disable-renderer-backgrounding"));
+        assert!(!base.contains("remote-debugging"));
+        assert!(webview2_browser_args(Some("9222")).ends_with(" --remote-debugging-port=9222"));
+        for bad in ["", "abc", "80", "70000", "9222 --evil", "-1"] {
+            assert_eq!(webview2_browser_args(Some(bad)), base, "{bad}");
+        }
+    }
+}
+
 #[cfg(test)]
 mod tray_tests {
     use super::*;