fix: --stats printed the u128 sentinel as the smallest file size

src/aggregate.rs

@@ -233,7 +233,9 @@ fn aggregate_inner(
     let total = aggregates.iter().map(|aggregate| aggregate.bytes).sum();
     res.num_errors = aggregates.iter().map(|aggregate| aggregate.errors).sum();
 
-    if stats.entries_traversed == 0 {
+    // Entries whose metadata could not be read never contribute a size, so counting them is not
+    // enough to know that the minimum was ever set - only the sentinel still being in place is.
+    if stats.smallest_file_in_bytes == u128::MAX {
         stats.smallest_file_in_bytes = 0;
     }
 
@@ -810,6 +812,44 @@ mod tests {
         assert_eq!(result.num_errors, 1);
     }
 
+    #[cfg(unix)]
+    #[test]
+    fn unreadable_roots_do_not_leak_the_smallest_file_sentinel() {
+        let dir = tempfile::tempdir().unwrap();
+        let root = dir.path().join("missing");
+
+        let (result, statistics) = aggregate(
+            Vec::new(),
+            None::<Vec<u8>>,
+            WalkOptions {
+                threads: 1,
+                count_hard_links: true,
+                apparent_size: true,
+                // Crossing filesystems keeps the root out of `crossdev::init`, so it fails while
+                // being walked and is counted as a traversed entry without a size.
+                cross_filesystems: true,
+                ignore_dirs: std::collections::BTreeSet::default(),
+                ignore_patterns: None,
+                metadata_options: crate::TraversalOptions::default(),
+            },
+            false,
+            true,
+            ByteFormat::Bytes,
+            vec![root],
+        )
+        .unwrap();
+
+        assert_eq!(result.num_errors, 1);
+        assert_eq!(
+            statistics.entries_traversed, 1,
+            "the failing root is seen, even though its size is unknown"
+        );
+        assert_eq!(
+            statistics.smallest_file_in_bytes, 0,
+            "no file size was ever observed, so the sentinel must not be reported as a size"
+        );
+    }
+
     #[test]
     fn ignored_patterns_are_left_out_of_the_reported_size() {
         let dir = tempfile::tempdir().unwrap();