fix(probe): do not hide prober failures or cover art

Review on #59. select_feature skipped every probe error, so a missing
ffprobe or a timeout reported "no video file" for a torrent that has
one; only per-file content failures are skipped now. And an audio file
with embedded artwork reports the cover as a video stream, which made a
soundtrack look importable.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

crates/arr-probe/src/error.rs

@@ -95,3 +95,24 @@ pub enum Error {
     #[error("no video file among the candidates")]
     NoCandidates,
 }
+
+impl Error {
+    /// Whether this failure is a fact about one file rather than about the
+    /// prober.
+    ///
+    /// Feature selection walks a torrent full of `.nfo`, `.jpg` and `.txt`
+    /// files, so a file that is not importable media is expected and gets
+    /// skipped. A missing binary, a timeout or unparseable output is not about
+    /// the file at all, and swallowing it would report "no video file" for a
+    /// torrent that has one.
+    #[must_use]
+    pub const fn is_about_the_file(&self) -> bool {
+        matches!(
+            self,
+            Self::Rejected { .. }
+                | Self::NotVideo { .. }
+                | Self::NoVideoStream { .. }
+                | Self::NoDuration { .. }
+        )
+    }
+}

crates/arr-probe/src/ffprobe.rs

@@ -35,6 +35,8 @@ pub(crate) struct Stream {
     pub color_transfer: Option<String>,
     pub duration: Option<String>,
     #[serde(default)]
+    pub disposition: Disposition,
+    #[serde(default)]
     pub tags: Tags,
     #[serde(default)]
     pub side_data_list: Vec<SideData>,
@@ -44,6 +46,20 @@ impl Stream {
     pub fn is_kind(&self, kind: &str) -> bool {
         self.codec_type.as_deref() == Some(kind)
     }
+
+    /// A real video stream, not the cover art bolted onto an audio file.
+    pub fn is_video(&self) -> bool {
+        self.is_kind("video") && self.disposition.attached_pic == 0
+    }
+}
+
+/// Stream flags. Only `attached_pic` is read: an MP3 or FLAC with embedded
+/// artwork reports it as a video stream, and taking that for video would make
+/// an audio file look importable.
+#[derive(Debug, Default, Deserialize)]
+pub(crate) struct Disposition {
+    #[serde(default)]
+    pub attached_pic: u8,
 }
 
 /// Stream metadata. Matroska writes `HANDLER_NAME`, MP4 writes `handler_name`,

crates/arr-probe/src/lib.rs

@@ -123,13 +123,15 @@ impl Prober {
     /// marked [`RuntimeMatch::Mismatched`]; deciding what to do about that is
     /// the import's call, not this crate's.
     ///
-    /// Paths `ffprobe` cannot read are skipped rather than failing the
-    /// selection — a torrent is full of `.nfo` and `.jpg` files.
+    /// Paths that are not importable media are skipped rather than failing the
+    /// selection — a torrent is full of `.nfo` and `.jpg` files. A failure of
+    /// the prober itself is not skipped: see [`Error::is_about_the_file`].
     ///
     /// # Errors
     ///
     /// [`Error::NoCandidates`] when no path in the set is a readable video
-    /// file.
+    /// file, and anything [`Prober::probe`] raises that is about the prober
+    /// rather than about one file.
     pub async fn select_feature(
         &self,
         paths: impl IntoIterator<Item = impl Into<PathBuf>>,
@@ -140,9 +142,10 @@ impl Prober {
             let path = path.into();
             match self.probe(path.clone()).await {
                 Ok(file) => candidates.push(file),
-                Err(error) => {
+                Err(error) if error.is_about_the_file() => {
                     tracing::debug!(path = %path.display(), %error, "not a video file, skipping");
                 }
+                Err(error) => return Err(error),
             }
         }
 

crates/arr-probe/src/model.rs

@@ -50,7 +50,7 @@ impl ProbedFile {
         let video = output
             .streams
             .iter()
-            .find(|stream| stream.is_kind("video"))
+            .find(|stream| stream.is_video())
             .ok_or_else(|| Error::NoVideoStream { path: path.clone() })?;
 
         let duration = duration(output).ok_or_else(|| Error::NoDuration { path: path.clone() })?;

crates/arr-probe/tests/probe.rs

@@ -128,6 +128,17 @@ async fn a_text_file_is_not_media() {
     assert!(matches!(error, Error::NotVideo { .. }), "{error:?}");
 }
 
+/// Cover art is a video stream as far as ffprobe is concerned.
+#[tokio::test]
+async fn an_audio_file_with_artwork_is_not_video() {
+    let error = Prober::new()
+        .probe(fixture("audio-with-cover.m4a"))
+        .await
+        .expect_err("an attached picture is not a video stream");
+
+    assert!(matches!(error, Error::NoVideoStream { .. }), "{error:?}");
+}
+
 #[tokio::test]
 async fn a_missing_file_is_an_error() {
     let error = Prober::new()
@@ -208,6 +219,19 @@ async fn nothing_within_tolerance_still_returns_the_largest_file() {
     );
 }
 
+/// A prober that cannot run is not the same fact as a torrent without video,
+/// and must not be reported as one.
+#[tokio::test]
+async fn a_broken_prober_fails_the_selection() {
+    let error = Prober::new()
+        .with_binary("ffprobe-that-does-not-exist")
+        .select_feature([fixture("movie-1080p.mkv")], None)
+        .await
+        .expect_err("nothing could be probed");
+
+    assert!(matches!(error, Error::Spawn { .. }), "{error:?}");
+}
+
 #[tokio::test]
 async fn a_torrent_with_no_video_file_selects_nothing() {
     let error = Prober::new()

scripts/make-probe-fixtures.sh

@@ -144,6 +144,15 @@ PY
 python3 "$work/dovi.py" "$work/base.mp4" "$out/dv-profile5.mp4" 5 0
 python3 "$work/dovi.py" "$work/base.mp4" "$out/dv-profile8-1.mp4" 8 1
 
+# An audio file with embedded artwork. ffprobe reports the cover as a video
+# stream, so this is what stops a soundtrack passing for a feature.
+ffmpeg -hide_banner -loglevel error -y \
+    -f lavfi -i "color=c=red:s=64x64:d=1" -frames:v 1 "$work/cover.jpg"
+ffmpeg -hide_banner -loglevel error -y \
+    -f lavfi -i "sine=frequency=440:duration=2" -i "$work/cover.jpg" \
+    -map 0:a -map 1:v -c:a aac -b:a 8k -c:v mjpeg -disposition:v attached_pic \
+    "$out/audio-with-cover.m4a"
+
 # Not media at all: the thing a multi-file torrent is full of.
 printf 'Release notes. Not a video file.\n' > "$out/notes.nfo"