1 files changed, 77 insertions, 0 deletions
diff --git a/crates/ra-mcp-engine/src/error.rs b/crates/ra-mcp-engine/src/error.rs
new file mode 100644
index 0000000..f40e1ae
--- /dev/null
+++ b/crates/ra-mcp-engine/src/error.rs
@@ -0,0 +1,77 @@
+use crate::lsp_transport::RpcErrorPayload;
+use ra_mcp_domain::{fault::Fault, types::InvariantViolation};
+use serde_json::Value;
+use thiserror::Error;
+
+/// Engine result type.
+pub type EngineResult<T> = Result<T, EngineError>;
+
+/// Structured rust-analyzer response error.
+#[derive(Debug, Clone, Error)]
+#[error("lsp response error: code={code}, message={message}")]
+pub struct LspResponseError {
+    /// LSP JSON-RPC error code.
+    pub code: i64,
+    /// LSP JSON-RPC error message.
+    pub message: String,
+    /// Optional JSON-RPC error data payload.
+    pub data: Option<Value>,
+}
+
+/// Engine failure type.
+#[derive(Debug, Error)]
+pub enum EngineError {
+    /// I/O failure while syncing source documents.
+    #[error("io error: {0}")]
+    Io(#[from] std::io::Error),
+    /// Domain invariant was violated.
+    #[error(transparent)]
+    Invariant(#[from] InvariantViolation),
+    /// Transport/process/protocol fault.
+    #[error("engine fault: {0:?}")]
+    Fault(Fault),
+    /// rust-analyzer returned a JSON-RPC error object.
+    #[error(transparent)]
+    LspResponse(#[from] LspResponseError),
+    /// Response payload could not be deserialized into expected type.
+    #[error("invalid lsp payload for method {method}: {message}")]
+    InvalidPayload {
+        /// Request method.
+        method: &'static str,
+        /// Decoder error detail.
+        message: String,
+    },
+    /// Request params could not be serialized into JSON.
+    #[error("invalid lsp request payload for method {method}: {message}")]
+    InvalidRequest {
+        /// Request method.
+        method: &'static str,
+        /// Encoder error detail.
+        message: String,
+    },
+    /// Path to URL conversion failed.
+    #[error("path cannot be represented as file URL")]
+    InvalidFileUrl,
+}
+
+impl From<Fault> for EngineError {
+    fn from(value: Fault) -> Self {
+        Self::Fault(value)
+    }
+}
+
+impl From<RpcErrorPayload> for LspResponseError {
+    fn from(value: RpcErrorPayload) -> Self {
+        Self {
+            code: value.code,
+            message: value.message,
+            data: value.data,
+        }
+    }
+}
+
+impl From<RpcErrorPayload> for EngineError {
+    fn from(value: RpcErrorPayload) -> Self {
+        Self::LspResponse(value.into())
+    }
+}