feat: report received mail links on stderr

src/mailto_links.rs

@@ -105,23 +105,43 @@ pub(super) fn receive_from_macos(app: &AppWindow) {
             return;
         };
         window_controller::activate(&app, None);
-        open(&app, [url]);
+        open(&app, "apple-event", [url]);
     });
 }
 
-/// Open mailto links in the composer as soon as it can take them.
-pub(super) fn open<S: AsRef<str>>(app: &AppWindow, uris: impl IntoIterator<Item = S>) {
-    let mut unreadable = false;
+/// Open mailto links in the composer as soon as it can take them. `source`
+/// says how they arrived ("message", "launch", "forwarded" or
+/// "apple-event") for the diagnostic line.
+pub(super) fn open<S: AsRef<str>>(
+    app: &AppWindow,
+    source: &'static str,
+    uris: impl IntoIterator<Item = S>,
+) {
+    let (mut received, mut unreadable) = (0_usize, 0_usize);
     LINKS.with(|links| {
         let mut links = links.borrow_mut();
         for uri in uris {
             match mailto::parse(uri.as_ref()) {
-                Some(message) => links.pending.push_back(message),
-                None => unreadable = true,
+                Some(message) => {
+                    links.pending.push_back(message);
+                    received += 1;
+                }
+                None => unreadable += 1,
             }
         }
     });
-    if unreadable {
+    if received + unreadable > 0 {
+        // Whether a link reached the application, without any of its
+        // content, like the FLECTAR_RENDERER lines.
+        eprintln!(
+            "FLECTAR_MAIL_LINKS {}",
+            serde_json::json!({
+                "event": "received", "source": source,
+                "links": received, "unreadable": unreadable,
+            })
+        );
+    }
+    if unreadable > 0 {
         app.set_render_status(UiMessage::plain("This email link is too long to open."));
     }
     open_pending_soon(app);

src/main.rs

@@ -1806,13 +1806,13 @@ pub fn run(platform: PlatformContext) -> Result<(), Box<dyn std::error::Error>>
         instance.serve(&runtime, move |activation| {
             let _ = app.upgrade_in_event_loop(move |app| {
                 window_controller::activate(&app, activation.activation_token);
-                mailto_links::open(&app, activation.links);
+                mailto_links::open(&app, "forwarded", activation.links);
             });
         });
     }
     // They open once the mail store is ready and the composer connected.
     #[cfg(desktop)]
-    mailto_links::open(&app, launch_links.unwrap_or_default());
+    mailto_links::open(&app, "launch", launch_links.unwrap_or_default());
     // The launcher's token was meant for this window: it lets the desktop
     // focus it (Wayland) and ends the launch feedback (X11).
     #[cfg(desktop)]

src/reader_validation.rs

@@ -842,7 +842,11 @@ fn mailto_links_open_without_losing_the_draft(
     app.set_compose_subject("My own subject".into());
     // The reader's link handler was replaced by a recorder above; open the
     // link the way it does.
-    mailto_links::open(app, ["mailto:second@example.com?attach=/etc/passwd"]);
+    mailto_links::open(
+        app,
+        "message",
+        ["mailto:second@example.com?attach=/etc/passwd"],
+    );
     frame();
     assert_eq!(
         *saved.borrow(),

src/renderer_input_controller.rs

@@ -116,7 +116,7 @@ pub(super) fn register_renderer_input_callbacks(
             return;
         }
         if flectar_mail_core::mailto::is_mailto(&url) {
-            crate::mailto_links::open(&app, [url.as_str()]);
+            crate::mailto_links::open(&app, "message", [url.as_str()]);
             return;
         }
         if let Err(error) = open_email_link(&opener, &url) {