[rust] Avoid panic in error case (#3133)

Author: frankfliu

extensions/tokenizers/rust/src/models/mod.rs

@@ -4,7 +4,7 @@ mod distilbert;
 use crate::ndarray::as_data_type;
 use crate::{cast_handle, to_handle, to_string_array};
 use bert::{BertConfig, BertModel};
-use candle_core::DType;
+use candle_core::{DType, Error};
 use candle_core::{Device, Result, Tensor};
 use candle_nn::VarBuilder;
 use distilbert::{DistilBertConfig, DistilBertModel};
@@ -43,7 +43,10 @@ fn load_model<'local>(
 
     // Load config
     let config: String = std::fs::read_to_string(model_path.join("config.json"))?;
-    let config: Config = serde_json::from_str(&config).unwrap();
+    let config: Config = match serde_json::from_str(&config) {
+        Ok(conf) => conf,
+        Err(err) => return Err(Error::wrap(err)),
+    };
 
     // Get candle device
     let device = if candle_core::utils::cuda_is_available() {
@@ -55,7 +58,7 @@ fn load_model<'local>(
     }?;
 
     // Get candle dtype
-    let dtype = as_data_type(dtype).unwrap();
+    let dtype = as_data_type(dtype)?;
 
     let safetensors_path = model_path.join("model.safetensors");
     let vb = if safetensors_path.exists() {

extensions/tokenizers/rust/src/ndarray/mod.rs

@@ -295,22 +295,30 @@ fn as_device<'local>(env: &mut JNIEnv<'local>, device_type: JString, _: usize) -
     match device_type.as_str() {
         "cpu" => Ok(Device::Cpu),
         "gpu" => {
-            let mut device = CUDA_DEVICE.lock().unwrap();
-            if let Some(device) = device.as_ref() {
-                return Ok(device.clone());
-            };
-            let d = Device::new_cuda(0).unwrap();
-            *device = Some(d.clone());
-            Ok(d)
+            if candle_core::utils::cuda_is_available() {
+                let mut device = CUDA_DEVICE.lock().unwrap();
+                if let Some(device) = device.as_ref() {
+                    return Ok(device.clone());
+                };
+                let d = Device::new_cuda(0).unwrap();
+                *device = Some(d.clone());
+                Ok(d)
+            } else {
+                Err(Error::Msg(String::from("CUDA is not available.")))
+            }
         }
         "mps" => {
-            let mut device = METAL_DEVICE.lock().unwrap();
-            if let Some(device) = device.as_ref() {
-                return Ok(device.clone());
-            };
-            let d = Device::new_metal(0).unwrap();
-            *device = Some(d.clone());
-            Ok(d)
+            if candle_core::utils::metal_is_available() {
+                let mut device = METAL_DEVICE.lock().unwrap();
+                if let Some(device) = device.as_ref() {
+                    return Ok(device.clone());
+                };
+                let d = Device::new_metal(0).unwrap();
+                *device = Some(d.clone());
+                Ok(d)
+            } else {
+                Err(Error::Msg(String::from("metal is not available.")))
+            }
         }
         _ => Err(Error::Msg(format!("Invalid device type: {}", device_type))),
     }

extensions/tokenizers/src/main/java/ai/djl/engine/rust/RsModel.java

@@ -49,6 +49,14 @@ public void load(Path modelPath, String prefix, Map<String, ?> options)
                     "Model directory doesn't exist: " + modelPath.toAbsolutePath());
         }
         modelDir = modelPath.toAbsolutePath();
+        Path config = modelDir.resolve("config.json");
+        if (!Files.isRegularFile(config)) {
+            throw new FileNotFoundException("config.json file not found");
+        }
+        Path file = modelDir.resolve("model.safetensors");
+        if (!Files.isRegularFile(file)) {
+            throw new FileNotFoundException("model.safetensors file not found");
+        }
         long handle = RustLibrary.loadModel(modelDir.toString(), dataType.ordinal());
         block = new RsSymbolBlock((RsNDManager) manager, handle);
     }