wiggle: allow user-configurable error transformations

crates/wiggle/tests/errors.rs

@@ -0,0 +1,35 @@
+use wiggle_test::{impl_errno, WasiCtx};
+
+#[derive(Debug, thiserror::Error)]
+pub enum RichError {
+    #[error("Invalid argument: {0}")]
+    InvalidArg(String),
+    #[error("Won't cross picket line: {0}")]
+    PicketLine(String),
+}
+
+wiggle::from_witx!({
+    witx: ["tests/arrays.witx"],
+    ctx: WasiCtx,
+    errors: { errno => RichError },
+});
+
+impl_errno!(types::Errno, types::GuestErrorConversion);
+
+impl<'a> types::UserErrorConversion for WasiCtx<'a> {
+    fn errno_from_rich_error(&self, _e: RichError) -> types::Errno {
+        unimplemented!();
+    }
+}
+
+impl<'a> arrays::Arrays for WasiCtx<'a> {
+    fn reduce_excuses(
+        &self,
+        _excuses: &types::ConstExcuseArray,
+    ) -> Result<types::Excuse, RichError> {
+        unimplemented!()
+    }
+    fn populate_excuses(&self, _excuses: &types::ExcuseArray) -> Result<(), RichError> {
+        unimplemented!()
+    }
+}