fix: optional file should be put in cache key to avoid internet access when prefer_local_files = true (#241)

* feat: when file is 404, cache as NotFound

* explicitly mark optional file

* refactor

crates/tabby-download/src/lib.rs

@@ -14,6 +14,7 @@ impl CacheInfo {
         model_id: &str,
         path: &str,
         prefer_local_file: bool,
+        is_optional: bool,
     ) -> Result<()> {
         // Create url.
         let url = format!("https://huggingface.co/{}/resolve/main/{}", model_id, path);
@@ -25,13 +26,22 @@ impl CacheInfo {
         let filepath = ModelDir::new(model_id).path_string(path);
 
         // Cache hit.
-        let mut local_file_ready = false;
-        if !prefer_local_file && local_cache_key.is_some() && fs::metadata(&filepath).is_ok() {
-            local_file_ready = true;
-        }
+        let local_file_ready = if prefer_local_file {
+            if let Some(local_cache_key) = local_cache_key {
+                if local_cache_key == "404" {
+                    true
+                } else {
+                    fs::metadata(&filepath).is_ok()
+                }
+            } else {
+                false
+            }
+        } else {
+            false
+        };
 
         if !local_file_ready {
-            let etag = download_file(&url, &filepath, local_cache_key).await?;
+            let etag = download_file(&url, &filepath, local_cache_key, is_optional).await?;
             self.set_local_cache_key(path, &etag).await;
         }
         Ok(())
@@ -46,39 +56,58 @@ pub async fn download_model(model_id: &str, prefer_local_file: bool) -> Result<(
 
     let mut cache_info = CacheInfo::from(model_id).await;
 
-    cache_info
-        .download(model_id, "tabby.json", prefer_local_file)
-        .await?;
-    cache_info
-        .download(model_id, "tokenizer.json", prefer_local_file)
-        .await?;
-    cache_info
-        .download(model_id, "ctranslate2/config.json", prefer_local_file)
-        .await?;
-    let _ = cache_info
-        .download(model_id, "ctranslate2/vocabulary.txt", prefer_local_file)
-        .await;
-    let _ = cache_info
-        .download(
-            model_id,
-            "ctranslate2/shared_vocabulary.txt",
-            prefer_local_file,
-        )
-        .await;
-    cache_info
-        .download(model_id, "ctranslate2/model.bin", prefer_local_file)
-        .await?;
-    cache_info.save(model_id)?;
+    let optional_files = vec![
+        "ctranslate2/vocabulary.txt",
+        "ctranslate2/shared_vocabulary.txt",
+    ];
+    for path in optional_files {
+        cache_info
+            .download(
+                model_id,
+                path,
+                prefer_local_file,
+                /* is_optional */ true,
+            )
+            .await?;
+    }
 
+    let required_files = vec![
+        "tabby.json",
+        "tokenizer.json",
+        "ctranslate2/config.json",
+        "ctranslate2/model.bin",
+    ];
+    for path in required_files {
+        cache_info
+            .download(
+                model_id,
+                path,
+                prefer_local_file,
+                /* required= */ false,
+            )
+            .await?;
+    }
+
+    cache_info.save(model_id)?;
     Ok(())
 }
 
-async fn download_file(url: &str, path: &str, local_cache_key: Option<&str>) -> Result<String> {
+async fn download_file(
+    url: &str,
+    path: &str,
+    local_cache_key: Option<&str>,
+    is_optional: bool,
+) -> Result<String> {
     fs::create_dir_all(Path::new(path).parent().unwrap())?;
 
     // Reqwest setup
     let res = reqwest::get(url).await?;
 
+    if is_optional && res.status() == 404 {
+        // Cache 404 for optional file.
+        return Ok("404".to_owned());
+    }
+
     if !res.status().is_success() {
         return Err(anyhow!(format!("Invalid url: {}", url)));
     }