Add anyhow-inspired error utilities

src/hyperlight_guest/src/error.rs

@@ -51,3 +51,294 @@ impl From<serde_json::Error> for HyperlightGuestError {
         }
     }
 }
+
+/// Extension trait to add context to `Option<T>` and `Result<T, E>` types in guest code,
+/// converting them to `Result<T, HyperlightGuestError>`.
+///
+/// This is similar to anyhow::Context.
+pub trait GuestErrorContext {
+    type Ok;
+    /// Adds context to the error if `self` is `None` or `Err`.
+    fn context(self, ctx: impl Into<String>) -> Result<Self::Ok>;
+    /// Adds context and a specific error code to the error if `self` is `None` or `Err`.
+    fn context_and_code(self, ec: ErrorCode, ctx: impl Into<String>) -> Result<Self::Ok>;
+    /// Lazily adds context to the error if `self` is `None` or `Err`.
+    ///
+    /// This is useful if constructing the context message is expensive.
+    fn with_context<S: Into<String>>(self, ctx: impl FnOnce() -> S) -> Result<Self::Ok>;
+    /// Lazily adds context and a specific error code to the error if `self` is `None` or `Err`.
+    ///
+    /// This is useful if constructing the context message is expensive.
+    fn with_context_and_code<S: Into<String>>(
+        self,
+        ec: ErrorCode,
+        ctx: impl FnOnce() -> S,
+    ) -> Result<Self::Ok>;
+}
+
+impl<T> GuestErrorContext for Option<T> {
+    type Ok = T;
+    #[inline]
+    fn context(self, ctx: impl Into<String>) -> Result<T> {
+        self.with_context_and_code(ErrorCode::GuestError, || ctx)
+    }
+    #[inline]
+    fn context_and_code(self, ec: ErrorCode, ctx: impl Into<String>) -> Result<T> {
+        self.with_context_and_code(ec, || ctx)
+    }
+    #[inline]
+    fn with_context<S: Into<String>>(self, ctx: impl FnOnce() -> S) -> Result<T> {
+        self.with_context_and_code(ErrorCode::GuestError, ctx)
+    }
+    #[inline]
+    fn with_context_and_code<S: Into<String>>(
+        self,
+        ec: ErrorCode,
+        ctx: impl FnOnce() -> S,
+    ) -> Result<Self::Ok> {
+        match self {
+            Some(s) => Ok(s),
+            None => Err(HyperlightGuestError::new(ec, ctx().into())),
+        }
+    }
+}
+
+impl<T, E: core::fmt::Debug> GuestErrorContext for core::result::Result<T, E> {
+    type Ok = T;
+    #[inline]
+    fn context(self, ctx: impl Into<String>) -> Result<T> {
+        self.with_context_and_code(ErrorCode::GuestError, || ctx)
+    }
+    #[inline]
+    fn context_and_code(self, ec: ErrorCode, ctx: impl Into<String>) -> Result<T> {
+        self.with_context_and_code(ec, || ctx)
+    }
+    #[inline]
+    fn with_context<S: Into<String>>(self, ctx: impl FnOnce() -> S) -> Result<T> {
+        self.with_context_and_code(ErrorCode::GuestError, ctx)
+    }
+    #[inline]
+    fn with_context_and_code<S: Into<String>>(
+        self,
+        ec: ErrorCode,
+        ctx: impl FnOnce() -> S,
+    ) -> Result<T> {
+        match self {
+            Ok(s) => Ok(s),
+            Err(e) => Err(HyperlightGuestError::new(
+                ec,
+                format!("{}.\nCaused by: {e:?}", ctx().into()),
+            )),
+        }
+    }
+}
+
+/// Macro to return early with a `Err(HyperlightGuestError)`.
+/// Usage:
+/// ```ignore
+/// bail!(ErrorCode::UnknownError => "An error occurred: {}", details);
+/// // or
+/// bail!("A guest error occurred: {}", details); // defaults to ErrorCode::GuestError
+/// ```
+#[macro_export]
+macro_rules! bail {
+    ($ec:expr => $($msg:tt)*) => {
+        return ::core::result::Result::Err($crate::error::HyperlightGuestError::new($ec, ::alloc::format!($($msg)*)));
+    };
+    ($($msg:tt)*) => {
+        $crate::bail!($crate::error::ErrorCode::GuestError => $($msg)*);
+    };
+}
+
+/// Macro to ensure a condition is true, otherwise returns early with a `Err(HyperlightGuestError)`.
+/// Usage:
+/// ```ignore
+/// ensure!(1 + 1 == 3, ErrorCode::UnknownError => "Maths is broken: {}", details);
+/// // or
+/// ensure!(1 + 1 == 3, "Maths is broken: {}", details); // defaults to ErrorCode::GuestError
+/// // or
+/// ensure!(1 + 1 == 3); // defaults to ErrorCode::GuestError with a default message
+/// ```
+#[macro_export]
+macro_rules! ensure {
+    ($cond:expr) => {
+        if !($cond) {
+            $crate::bail!(::core::concat!("Condition failed: `", ::core::stringify!($cond), "`"));
+        }
+    };
+    ($cond:expr, $ec:expr => $($msg:tt)*) => {
+        if !($cond) {
+            $crate::bail!($ec => ::core::concat!("{}\nCaused by failed condition: `", ::core::stringify!($cond), "`"), ::core::format_args!($($msg)*));
+        }
+    };
+    ($cond:expr, $($msg:tt)*) => {
+        $crate::ensure!($cond, $crate::error::ErrorCode::GuestError => $($msg)*);
+    };
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_context_option_some() {
+        let value: Option<u32> = Some(42);
+        let result = value.context("Should be Some");
+        assert_eq!(result.unwrap(), 42);
+    }
+
+    #[test]
+    fn test_context_option_none() {
+        let value: Option<u32> = None;
+        let result = value.context("Should be Some");
+        let err = result.unwrap_err();
+        assert_eq!(err.kind, ErrorCode::GuestError);
+        assert_eq!(err.message, "Should be Some");
+    }
+
+    #[test]
+    fn test_context_and_code_option_none() {
+        let value: Option<u32> = None;
+        let result = value.context_and_code(ErrorCode::MallocFailed, "Should be Some");
+        let err = result.unwrap_err();
+        assert_eq!(err.kind, ErrorCode::MallocFailed);
+        assert_eq!(err.message, "Should be Some");
+    }
+
+    #[test]
+    fn test_with_context_option_none() {
+        let value: Option<u32> = None;
+        let result = value.with_context(|| "Lazy context message");
+        let err = result.unwrap_err();
+        assert_eq!(err.kind, ErrorCode::GuestError);
+        assert_eq!(err.message, "Lazy context message");
+    }
+
+    #[test]
+    fn test_with_context_and_code_option_none() {
+        let value: Option<u32> = None;
+        let result =
+            value.with_context_and_code(ErrorCode::MallocFailed, || "Lazy context message");
+        let err = result.unwrap_err();
+        assert_eq!(err.kind, ErrorCode::MallocFailed);
+        assert_eq!(err.message, "Lazy context message");
+    }
+
+    #[test]
+    fn test_context_result_ok() {
+        let value: core::result::Result<u32, &str> = Ok(42);
+        let result = value.context("Should be Ok");
+        assert_eq!(result.unwrap(), 42);
+    }
+
+    #[test]
+    fn test_context_result_err() {
+        let value: core::result::Result<u32, &str> = Err("Some error");
+        let result = value.context("Should be Ok");
+        let err = result.unwrap_err();
+        assert_eq!(err.kind, ErrorCode::GuestError);
+        assert_eq!(err.message, "Should be Ok.\nCaused by: \"Some error\"");
+    }
+
+    #[test]
+    fn test_context_and_code_result_err() {
+        let value: core::result::Result<u32, &str> = Err("Some error");
+        let result = value.context_and_code(ErrorCode::MallocFailed, "Should be Ok");
+        let err = result.unwrap_err();
+        assert_eq!(err.kind, ErrorCode::MallocFailed);
+        assert_eq!(err.message, "Should be Ok.\nCaused by: \"Some error\"");
+    }
+
+    #[test]
+    fn test_with_context_result_err() {
+        let value: core::result::Result<u32, &str> = Err("Some error");
+        let result = value.with_context(|| "Lazy context message");
+        let err = result.unwrap_err();
+        assert_eq!(err.kind, ErrorCode::GuestError);
+        assert_eq!(
+            err.message,
+            "Lazy context message.\nCaused by: \"Some error\""
+        );
+    }
+
+    #[test]
+    fn test_with_context_and_code_result_err() {
+        let value: core::result::Result<u32, &str> = Err("Some error");
+        let result =
+            value.with_context_and_code(ErrorCode::MallocFailed, || "Lazy context message");
+        let err = result.unwrap_err();
+        assert_eq!(err.kind, ErrorCode::MallocFailed);
+        assert_eq!(
+            err.message,
+            "Lazy context message.\nCaused by: \"Some error\""
+        );
+    }
+
+    #[test]
+    fn test_bail_macro() {
+        let result: Result<u32> = (|| {
+            bail!("A guest error occurred");
+        })();
+        let err = result.unwrap_err();
+        assert_eq!(err.kind, ErrorCode::GuestError);
+        assert_eq!(err.message, "A guest error occurred");
+    }
+
+    #[test]
+    fn test_bail_macro_with_error_code() {
+        let result: Result<u32> = (|| {
+            bail!(ErrorCode::MallocFailed => "Memory allocation failed");
+        })();
+        let err = result.unwrap_err();
+        assert_eq!(err.kind, ErrorCode::MallocFailed);
+        assert_eq!(err.message, "Memory allocation failed");
+    }
+
+    #[test]
+    fn test_ensure_macro_pass() {
+        let result: Result<u32> = (|| {
+            ensure!(1 + 1 == 2, "Math works");
+            Ok(42)
+        })();
+        assert_eq!(result.unwrap(), 42);
+    }
+
+    #[test]
+    fn test_ensure_macro_fail() {
+        let result: Result<u32> = (|| {
+            ensure!(1 + 1 == 3, "Math is broken");
+            Ok(42)
+        })();
+        let err = result.unwrap_err();
+        assert_eq!(err.kind, ErrorCode::GuestError);
+        assert_eq!(
+            err.message,
+            "Math is broken\nCaused by failed condition: `1 + 1 == 3`"
+        );
+    }
+
+    #[test]
+    fn test_ensure_macro_fail_no_message() {
+        let result: Result<u32> = (|| {
+            ensure!(1 + 1 == 3);
+            Ok(42)
+        })();
+        let err = result.unwrap_err();
+        assert_eq!(err.kind, ErrorCode::GuestError);
+        assert_eq!(err.message, "Condition failed: `1 + 1 == 3`");
+    }
+
+    #[test]
+    fn test_ensure_macro_fail_with_error_code() {
+        let result: Result<u32> = (|| {
+            ensure!(1 + 1 == 3, ErrorCode::UnknownError => "Math is broken");
+            Ok(42)
+        })();
+        let err = result.unwrap_err();
+        assert_eq!(err.kind, ErrorCode::UnknownError);
+        assert_eq!(
+            err.message,
+            "Math is broken\nCaused by failed condition: `1 + 1 == 3`"
+        );
+    }
+}