A feed's own artwork has to be there before it is used (#89)

A feed's itunes:image or <image><url> was stored without being asked
for, so a dead one stood in the way of the site's icon. Ken and Robin
Talk About Stuff names http://kenandrobin.wpengine.com/.../kartas_podcast.png,
a 404, while its site's apple-touch-icon works. The feed's artwork now has
to answer as an image, as the site icon already did, when the feed is
read in full; otherwise the site's icon is looked for.

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

CHANGELOG.md

@@ -42,6 +42,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+- A feed whose own artwork is missing shows its website's icon instead of nothing.
 - The log has no terminal colour codes when it is not going to a terminal, as in `docker logs`.
 - A feed whose website names an icon that is missing shows the site's `/favicon.ico` instead of
   no artwork.

src/feed.rs

@@ -385,19 +385,19 @@ pub async fn site_icon(client: &reqwest::Client, site: &str) -> Option<String> {
         && let Ok(page) = resp.bytes().await
         && let Some(href) = page_icon(&page)
         && let Ok(url) = base.join(&href)
-        && is_image(client, &url).await
+        && is_image(client, url.as_str()).await
     {
         return Some(url.into());
     }
     let ico = base.join("/favicon.ico").ok()?;
-    is_image(client, &ico).await.then(|| ico.into())
+    is_image(client, ico.as_str()).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 {
+pub async fn is_image(client: &reqwest::Client, url: &str) -> bool {
     let timeout = std::time::Duration::from_secs(20);
-    let Ok(resp) = client.get(url.clone()).timeout(timeout).send().await else { return false };
+    let Ok(resp) = client.get(url).timeout(timeout).send().await else { return false };
     resp.status().is_success()
         && resp
             .headers()

src/main.rs

@@ -1258,6 +1258,14 @@ async fn scan_one(
     // is stored as "", which the page draws as no art, and which stops the refetch above.
     // ponytail: a feed without validators is read in full every scan and asks its site each
     // time too; keep a checked-at time per feed if that shows up in anyone's logs.
+    // A feed's own artwork has to be there too: Ken and Robin's names a 404, and stored unasked
+    // it stood in the way of the site's icon, which works (#89).
+    if let Some(art) = &parsed.image
+        && !feed::is_image(&ctx.client, art).await
+    {
+        tracing::info!(feed = id, art = %art, "the feed's artwork is not an image; trying its site's icon");
+        parsed.image = None;
+    }
     if parsed.image.is_none() {
         parsed.image = Some(match &parsed.site {
             Some(site) => feed::site_icon(&ctx.client, site).await.unwrap_or_default(),