Don't trigger authentication flow unless credentials expired (#35570)

This fixes a regression introduced in
https://github.com/zed-industries/zed/pull/35471, where we treated
stored credentials as invalid when failing to retrieve the authenticated
user for any reason. This had the side effect of triggering the auth
flow even when e.g. the client/server had temporary networking issues.

This pull request changes the logic to only trigger authentication when
getting a 401 from the server.

Release Notes:

- N/A

crates/client/src/client.rs

@@ -884,27 +884,28 @@ impl Client {
 
         let old_credentials = self.state.read().credentials.clone();
         if let Some(old_credentials) = old_credentials {
-            self.cloud_client.set_credentials(
-                old_credentials.user_id as u32,
-                old_credentials.access_token.clone(),
-            );
-
-            // Fetch the authenticated user with the old credentials, to ensure they are still valid.
-            if self.cloud_client.get_authenticated_user().await.is_ok() {
+            if self
+                .cloud_client
+                .validate_credentials(
+                    old_credentials.user_id as u32,
+                    &old_credentials.access_token,
+                )
+                .await?
+            {
                 credentials = Some(old_credentials);
             }
         }
 
         if credentials.is_none() && try_provider {
             if let Some(stored_credentials) = self.credentials_provider.read_credentials(cx).await {
-                self.cloud_client.set_credentials(
-                    stored_credentials.user_id as u32,
-                    stored_credentials.access_token.clone(),
-                );
-
-                // Fetch the authenticated user with the stored credentials, and
-                // clear them from the credentials provider if that fails.
-                if self.cloud_client.get_authenticated_user().await.is_ok() {
+                if self
+                    .cloud_client
+                    .validate_credentials(
+                        stored_credentials.user_id as u32,
+                        &stored_credentials.access_token,
+                    )
+                    .await?
+                {
                     credentials = Some(stored_credentials);
                 } else {
                     self.credentials_provider
@@ -1709,7 +1710,7 @@ pub fn parse_zed_link<'a>(link: &'a str, cx: &App) -> Option<&'a str> {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::test::FakeServer;
+    use crate::test::{FakeServer, parse_authorization_header};
 
     use clock::FakeSystemClock;
     use gpui::{AppContext as _, BackgroundExecutor, TestAppContext};
@@ -1835,6 +1836,75 @@ mod tests {
         ));
     }
 
+    #[gpui::test(iterations = 10)]
+    async fn test_reauthenticate_only_if_unauthorized(cx: &mut TestAppContext) {
+        init_test(cx);
+        let auth_count = Arc::new(Mutex::new(0));
+        let http_client = FakeHttpClient::create(|_request| async move {
+            Ok(http_client::Response::builder()
+                .status(200)
+                .body("".into())
+                .unwrap())
+        });
+        let client =
+            cx.update(|cx| Client::new(Arc::new(FakeSystemClock::new()), http_client.clone(), cx));
+        client.override_authenticate({
+            let auth_count = auth_count.clone();
+            move |cx| {
+                let auth_count = auth_count.clone();
+                cx.background_spawn(async move {
+                    *auth_count.lock() += 1;
+                    Ok(Credentials {
+                        user_id: 1,
+                        access_token: auth_count.lock().to_string(),
+                    })
+                })
+            }
+        });
+
+        let credentials = client.sign_in(false, &cx.to_async()).await.unwrap();
+        assert_eq!(*auth_count.lock(), 1);
+        assert_eq!(credentials.access_token, "1");
+
+        // If credentials are still valid, signing in doesn't trigger authentication.
+        let credentials = client.sign_in(false, &cx.to_async()).await.unwrap();
+        assert_eq!(*auth_count.lock(), 1);
+        assert_eq!(credentials.access_token, "1");
+
+        // If the server is unavailable, signing in doesn't trigger authentication.
+        http_client
+            .as_fake()
+            .replace_handler(|_, _request| async move {
+                Ok(http_client::Response::builder()
+                    .status(503)
+                    .body("".into())
+                    .unwrap())
+            });
+        client.sign_in(false, &cx.to_async()).await.unwrap_err();
+        assert_eq!(*auth_count.lock(), 1);
+
+        // If credentials became invalid, signing in triggers authentication.
+        http_client
+            .as_fake()
+            .replace_handler(|_, request| async move {
+                let credentials = parse_authorization_header(&request).unwrap();
+                if credentials.access_token == "2" {
+                    Ok(http_client::Response::builder()
+                        .status(200)
+                        .body("".into())
+                        .unwrap())
+                } else {
+                    Ok(http_client::Response::builder()
+                        .status(401)
+                        .body("".into())
+                        .unwrap())
+                }
+            });
+        let credentials = client.sign_in(false, &cx.to_async()).await.unwrap();
+        assert_eq!(*auth_count.lock(), 2);
+        assert_eq!(credentials.access_token, "2");
+    }
+
     #[gpui::test(iterations = 10)]
     async fn test_authenticating_more_than_once(
         cx: &mut TestAppContext,