chore(download): properly implement partitioned model download (Tabby…

…ML#3294)

* bug: fix ignored local model

* feat: should redownload if part of models not found

* test: fix sha256 check returned error

* [autofix.ci] apply automated fixes

* [autofix.ci] apply automated fixes (attempt 2/3)

---------

Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>

crates/aim-downloader/src/hash.rs

@@ -9,7 +9,7 @@ impl HashChecker {
     pub fn check(filename: &str, expected_hash: &str) -> Result<(), ValidateError> {
         let mut result = Ok(());
         if filename != "stdout" && (!expected_hash.is_empty()) {
-            let actual_hash = HashChecker::sha256sum(filename);
+            let actual_hash = HashChecker::sha256sum(filename)?;
             if actual_hash != expected_hash {
                 result = Err(ValidateError::Sha256Mismatch);
             }
@@ -22,15 +22,21 @@ impl HashChecker {
         result
     }
 
-    fn sha256sum(filename: &str) -> String {
+    fn sha256sum(filename: &str) -> Result<String, ValidateError> {
         let mut hasher = Sha256::new();
-        let mut file = fs::File::open(filename).unwrap();
-
-        io::copy(&mut file, &mut hasher).unwrap();
+        let mut file = fs::File::open(filename).map_err(|e| {
+            println!("Can not open {filename}:\n  {e}");
+            ValidateError::Sha256Mismatch
+        })?;
+
+        io::copy(&mut file, &mut hasher).map_err(|e| {
+            println!("Can not read {filename}:\n  {e}");
+            ValidateError::Sha256Mismatch
+        })?;
         let computed_hash = hasher.finalize();
         drop(file);
 
-        format!("{computed_hash:x}")
+        Ok(format!("{computed_hash:x}"))
     }
 }
 
@@ -61,7 +67,7 @@ mod tests {
     fn test_sha256sum_api() {
         let expected = "21d7847124bfb9d9a9d44af6f00d8003006c44b9ef9ba458b5d4d3fc5f81bde5";
 
-        let actual = HashChecker::sha256sum("LICENCE.md");
+        let actual = HashChecker::sha256sum("LICENCE.md").unwrap();
 
         assert_eq!(actual, expected);
     }

crates/tabby-download/src/lib.rs

@@ -85,34 +85,45 @@ async fn download_model_impl(
         );
     }
 
-    if !prefer_local_file {
-        info!("Checking model integrity..");
-
-        let mut sha256_matched = true;
-        for (index, url) in urls.iter().enumerate() {
-            if HashChecker::check(
-                partitioned_file_name!(index + 1, urls.len()).as_str(),
-                &url.1,
-            )
-            .is_err()
-            {
-                sha256_matched = false;
-                break;
-            }
+    let mut model_existed = true;
+    for (index, _) in urls.iter().enumerate() {
+        if fs::metadata(
+            registry
+                .get_model_store_dir(name)
+                .join(partitioned_file_name!(index, urls.len())),
+        )
+        .is_err()
+        {
+            model_existed = false;
+            break;
         }
+    }
 
-        if sha256_matched {
-            return Ok(());
-        }
+    if model_existed && prefer_local_file {
+        return Ok(());
+    }
 
-        warn!(
-            "Checksum doesn't match for <{}/{}>, re-downloading...",
-            registry.name, name
-        );
+    info!("Checking model integrity..");
 
-        fs::remove_dir_all(registry.get_model_dir(name))?;
+    let mut sha256_matched = true;
+    for (index, url) in urls.iter().enumerate() {
+        if HashChecker::check(partitioned_file_name!(index, urls.len()).as_str(), &url.1).is_err() {
+            sha256_matched = false;
+            break;
+        }
+    }
+
+    if sha256_matched {
+        return Ok(());
     }
 
+    warn!(
+        "Checksum doesn't match for <{}/{}>, re-downloading...",
+        registry.name, name
+    );
+
+    fs::remove_dir_all(registry.get_model_dir(name))?;
+
     // prepare for download
     let dir = registry.get_model_store_dir(name);
     fs::create_dir_all(dir)?;
@@ -123,7 +134,7 @@ async fn download_model_impl(
             .get_model_store_dir(name)
             .to_string_lossy()
             .into_owned();
-        let filename: String = partitioned_file_name!(index + 1, urls.len());
+        let filename: String = partitioned_file_name!(index, urls.len());
         let strategy = ExponentialBackoff::from_millis(100).map(jitter).take(2);
 
         Retry::spawn(strategy, move || {