fix(pixiv): keep a frame-zip download hiccup retryable

download_media_to_file's non-transport errors all folded into PixivError::Api, and Api is permanent in pixiv_error_is_retryable — so one 429/5xx, stalled transfer or temp-file write failure while fetching the ugoira frame zip permanently failed the whole post, while the bot's own upload downloads classify the very same classes as retryable (classify_download_error). A new PixivError::Transient carries those classes into the existing retry policy (and into startup validation's 'stays enabled' branch); Http keeps its arm and everything else stays permanent. The retryable table and the startup-validation loop pin both halves.

crates/x-media/src/site/pixiv/api.rs

@@ -39,6 +39,11 @@ pub enum PixivError {
     Status(u16),
     #[error("pixiv api error: {0}")]
     Api(String),
+    /// A bad moment while preparing media: a transient download status
+    /// (429 / 5xx), a stalled transfer or a temp-file write failure. A retry
+    /// can change the answer, so the pixiv retry policy re-fetches these.
+    #[error("transient pixiv error: {0}")]
+    Transient(String),
 }
 
 /// Native pixiv app-API client.
@@ -228,6 +233,14 @@ impl PixivAPI {
             .await
             .map_err(|e| match e {
                 FetchError::Http(e) => PixivError::Http(e),
+                // A bad moment (429/5xx, a stalled transfer, a temp-file
+                // write failure) must stay retryable: folding it into Api
+                // made one hiccup permanently fail the whole ugoira post,
+                // while the bot's own upload downloads retry the same
+                // classes.
+                transient @ (FetchError::Transient(_) | FetchError::Io(_)) => {
+                    PixivError::Transient(format!("frame zip download failed: {transient}"))
+                }
                 other => PixivError::Api(format!("frame zip download failed: {other}")),
             })?;
         let frame_delays = metadata.frames.iter().map(|f| f.delay).collect::<Vec<_>>();

crates/x-media/src/site/pixiv/interface.rs

@@ -102,7 +102,7 @@ pub fn is_retryable(err: &FetchError) -> bool {
 /// rejected credential is not.
 fn pixiv_error_is_retryable(err: &PixivError) -> bool {
     match err {
-        PixivError::Http(_) => true,
+        PixivError::Http(_) | PixivError::Transient(_) => true,
         PixivError::Status(code) if *code == 429 || *code >= 500 => true,
         PixivError::Status(_) | PixivError::Api(_) | PixivError::Json(_) | PixivError::NoAuth => {
             false
@@ -443,7 +443,11 @@ mod tests {
         // it calls `disable()`, a process-wide flag with no reset, so a test
         // touching it would order-couple every other pixiv test (the predicate
         // it keys on is covered by the table below).
-        for err in [PixivError::Status(429), PixivError::Status(503)] {
+        for err in [
+            PixivError::Status(429),
+            PixivError::Status(503),
+            PixivError::Transient("frame zip download failed: transient".into()),
+        ] {
             let enabled_before = api::enabled();
             let message = startup_validation(Err(err)).unwrap_err();
             assert!(message.contains("stays enabled"), "{message}");
@@ -458,11 +462,15 @@ mod tests {
 
     #[test]
     fn is_retryable_classifies_transient_and_permanent() {
-        // Transient: network errors, explicit transient, pixiv 429/5xx.
+        // Transient: network errors, explicit transient, pixiv 429/5xx, and a
+        // failed media download (the frame zip's own bad moment).
         assert!(is_retryable(&FetchError::Transient("429".into())));
         assert!(is_retryable(&FetchError::Pixiv(PixivError::Status(429))));
         assert!(is_retryable(&FetchError::Pixiv(PixivError::Status(500))));
         assert!(is_retryable(&FetchError::Pixiv(PixivError::Status(503))));
+        assert!(is_retryable(&FetchError::Pixiv(PixivError::Transient(
+            "frame zip download failed: transient: media status 429".into()
+        ))));
         // Permanent: pixiv 4xx (bad/expired token, forbidden, not found),
         // api/auth errors, unparseable bodies, not-found/blocked/sensitive.
         assert!(!is_retryable(&FetchError::Pixiv(PixivError::Status(400))));