A site icon that is missing is not used (#79)

site_icon took the icon a site's page names in its <link> tags without
asking for it, so a dead one was stored and /favicon.ico never tried.
antirez.com names /images/favicon.png, which is a 404, while its
/favicon.ico is there; the feed showed no artwork, and since the lookup
happens once, never would. The named icon now has to answer with an
image, as /favicon.ico already did.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

CHANGELOG.md

@@ -32,6 +32,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+- A feed whose website names an icon that is missing shows the site's `/favicon.ico` instead of
+  no artwork.
 - The read button shows whether an item is read, as the pin beside it shows whether it is
   pinned: a tick when read, an envelope when not. It used to show the opposite.
 - In Directory and Popular, Subscribe is a plus again, not the tick that marks a feed you have.

src/feed.rs

@@ -377,22 +377,31 @@ pub async fn site_icon(client: &reqwest::Client, site: &str) -> Option<String> {
     // Relative to where the page ended up, not where it was asked for: a site that redirects
     // to /en/ would otherwise have its icon looked for in the wrong place.
     let base = resp.url().clone();
+    // The icon a page names can be gone: antirez.com names /images/favicon.png, a 404, while its
+    // /favicon.ico is there. Stored unchecked, it was a broken image that was never looked up again.
     if resp.status().is_success()
         && let Ok(page) = resp.bytes().await
         && let Some(href) = page_icon(&page)
         && let Ok(url) = base.join(&href)
+        && is_image(client, &url).await
     {
         return Some(url.into());
     }
     let ico = base.join("/favicon.ico").ok()?;
-    let resp = client.get(ico.clone()).timeout(timeout).send().await.ok()?;
-    let is_image = resp
-        .headers()
-        .get(reqwest::header::CONTENT_TYPE)
-        .and_then(|v| v.to_str().ok())
-        .is_some_and(|t| t.starts_with("image/"));
-    // A site with no favicon often answers 200 with its home page, which is not an icon.
-    (resp.status().is_success() && is_image).then(|| ico.into())
+    is_image(client, &ico).await.then(|| ico.into())
+}
+
+/// Whether `url` answers with an image. A site with no favicon often answers 200 with its home
+/// page, which is not an icon.
+async fn is_image(client: &reqwest::Client, url: &reqwest::Url) -> bool {
+    let timeout = std::time::Duration::from_secs(20);
+    let Ok(resp) = client.get(url.clone()).timeout(timeout).send().await else { return false };
+    resp.status().is_success()
+        && resp
+            .headers()
+            .get(reqwest::header::CONTENT_TYPE)
+            .and_then(|v| v.to_str().ok())
+            .is_some_and(|t| t.starts_with("image/"))
 }
 
 /// The icon a web page names in its `<link>` tags, the larger apple-touch-icon first: a plain