Expose fallibility of individual SQL results

`LocalGeneration::sql::files()` runs an SQL query, iterates over the
results and collects the rows into a `Vec`. This can fail at any step:
the query might fail to run, or one of the rows might fail to be fetched
or processed.

Right now, we lump all those failures into a `Result` that wraps the
whole return value. This is only possible because we process each row
before returning. Once `Vec` is replaced by an iterator, we won't have
that luxury anymore, so we now wrap each individual element into its own
`Result` (as well as wrapping the whole vector into a `Result` of its
own).

1 files changed, 10 insertions, 7 deletions

diff --git a/src/cmd/show_gen.rs b/src/cmd/show_gen.rs
index ba39809..7dc52cf 100644
--- a/src/cmd/show_gen.rs
+++ b/src/cmd/show_gen.rs
@@ -23,14 +23,17 @@ impl ShowGeneration {
         let gen = client.fetch_generation(&gen_id, temp.path())?;
         let files = gen.files()?;
 
-        let total_bytes = files.iter().fold(0, |acc, file| {
-            let e = file.entry();
-            if e.kind() == FilesystemKind::Regular {
-                acc + file.entry().len()
-            } else {
-                acc
-            }
+        let total_bytes = files.into_iter().try_fold(0, |acc, file| {
+            file.map(|file| {
+                let e = file.entry();
+                if e.kind() == FilesystemKind::Regular {
+                    acc + e.len()
+                } else {
+                    acc
+                }
+            })
         });
+        let total_bytes = total_bytes?;
 
         println!("generation-id: {}", gen_id);
         println!("file-count: {}", gen.file_count()?);