feat compile-time feature-gated Rust backtrace for JNI error diagnostics

Author: summaryzb

java/lance-jni/Cargo.toml

@@ -16,15 +16,15 @@ crate-type = ["cdylib"]
 default = []
 
 [dependencies]
-lance = { path = "../../rust/lance", features = ["substrait"] }
+lance = { path = "../../rust/lance", features = ["substrait", "backtrace"] }
 lance-datafusion = { path = "../../rust/lance-datafusion" }
 lance-encoding = { path = "../../rust/lance-encoding" }
 lance-linalg = { path = "../../rust/lance-linalg" }
 lance-index = { path = "../../rust/lance-index" }
 lance-io = { path = "../../rust/lance-io" }
 lance-namespace = { path = "../../rust/lance-namespace" }
 lance-namespace-impls = { path = "../../rust/lance-namespace-impls", features = ["rest", "rest-adapter"] }
-lance-core = { path = "../../rust/lance-core" }
+lance-core = { path = "../../rust/lance-core", features = ["backtrace"] }
 lance-file = { path = "../../rust/lance-file" }
 lance-table = { path = "../../rust/lance-table" }
 arrow = { version = "57.1", features = ["ffi"] }
@@ -51,7 +51,7 @@ prost-types = "0.14.1"
 chrono = "0.4.41"
 
 [profile.dev]
-debug = "line-tables-only"
+debug = true
 incremental = false
 
 # This rule applies to every package except workspace members (dependencies

java/lance-jni/src/error.rs

@@ -175,28 +175,36 @@ impl std::fmt::Display for Error {
 
 impl From<LanceError> for Error {
     fn from(err: LanceError) -> Self {
+        let backtrace_suffix = err
+            .backtrace()
+            .map(|bt| format!("\n\nRust backtrace:\n{}", bt))
+            .unwrap_or_default();
+        let message = format!("{}{}", err, backtrace_suffix);
+
         match &err {
             LanceError::DatasetNotFound { .. }
             | LanceError::DatasetAlreadyExists { .. }
             | LanceError::CommitConflict { .. }
-            | LanceError::InvalidInput { .. } => Self::input_error(err.to_string()),
-            LanceError::IO { .. } => Self::io_error(err.to_string()),
-            LanceError::NotSupported { .. } => Self::unsupported_error(err.to_string()),
-            LanceError::NotFound { .. } => Self::io_error(err.to_string()),
+            | LanceError::InvalidInput { .. } => Self::input_error(message),
+            LanceError::IO { .. } => Self::io_error(message),
+            LanceError::NotSupported { .. } => Self::unsupported_error(message),
+            LanceError::NotFound { .. } => Self::io_error(message),
             LanceError::Namespace { source, .. } => {
                 // Try to downcast to NamespaceError and get the error code
                 if let Some(ns_err) = source.downcast_ref::<NamespaceError>() {
-                    Self::namespace_error(ns_err.code().as_u32(), ns_err.to_string())
+                    let ns_message =
+                        format!("{}{}", ns_err, backtrace_suffix);
+                    Self::namespace_error(ns_err.code().as_u32(), ns_message)
                 } else {
                     log::warn!(
                         "Failed to downcast NamespaceError source, falling back to runtime error. \
                          This may indicate a version mismatch. Source type: {:?}",
                         source
                     );
-                    Self::runtime_error(err.to_string())
+                    Self::runtime_error(message)
                 }
             }
-            _ => Self::runtime_error(err.to_string()),
+            _ => Self::runtime_error(message),
         }
     }
 }

rust/lance-core/Cargo.toml

@@ -55,6 +55,10 @@ proptest.workspace = true
 rstest.workspace = true
 
 [features]
+# Capture Rust backtraces in error types. When disabled (the default),
+# the backtrace field is zero-sized with no overhead. At runtime, capture
+# is still gated by RUST_BACKTRACE=1.
+backtrace = []
 datafusion = ["dep:datafusion-common", "dep:datafusion-sql"]
 
 [lints]